Head Gasket vs Cracked Engine Block
 

Is there a way for me to tell if I have a cracked engine block or is it a head gasket job I need on my 1991 300 SE

Symptoms: When the car is at a red light the temp guage goes up. When the light changes to green and I accelerate, the temp gauge goes back down. I was told about 3 years ago by a Mercedes Dealer that I needed a head gasket. This is a "second car" to me, I don't drive it that much. The problem has stayed the same, it does not appear to have gotten any worse or better over all this time. I am a bit hesitant to believe the dealer because I also have a Mazda and oddly enough around the same time a Mazda Dealer told me that my Mazda needed a head gasket and I have found out that was not true.

My 3000 SE is really starting to go through coolant. I normally only drive it once a week and that is just around the block but I find that I need to put coolant in the overflow every week. When I moved the car today I could tell that the coolant was leaking from further back and not by the front of the car. When I took the car in to the Mercedes dealer 3 years ago they also told me I needed a radiator and a water pump.

My concern about a cracked engine block is this. About 3 months ago I had taken the car around the block and I did not know it, but the overflow was bone dry and the car heated up and went into the hot. I shut it down right away. Since then, it has continued to do what it has always done. It runs ok until I am at a stop light then heats up but once I accelerate the temp gauge goes back down.

If I cracked my engine block - would the car even run?

It sounds to me that you may need a new water pump. If you had a cracked block you would find coolent in the engine oil and oil floating in the overflow tank for the radiator. Have you checked the belt. Check the color of your oil. How old are the hoses?

92 300E 139,000
77 Datsun 280 2+2 68,000
02 Dodge Quad 4 By 4
04 Expedition 4 by 4 38,000
00 Mustang 6 198,000
05 Mustang G.T. 23,000
89 Jeep Pick up 198,000

I don't know how old the hoses are, I did have a major tune up done on it about 2 1/2 years ago. I needed to replace the distributor cap and it had been awhile since I had a tune up so I did that, as well as a transmission service and got all new plugs.

I do keep an eye on the oil and it looks pretty clean to me. And I really don't seem to loose oil. It's about half way between full and low.

As far as I can tell, I can't see any oil in the overflow tank. What I do see is the coolant level going down.

I had a transmission guy driving my Miata several months ago and I was describing the symptoms of my Benz to him and he said it sounded like a water pump. This was before I drove it that one time without there being any coolant in it. I did take the cap off the overflow when it was really hot, but it was empty. I don't think anything happened, because nothing came out.

Which belt should I check? I'm not afraid to go looking around under my hood.

One other thing I have noticed under there is the long black cover over the plugs seems to be loose or it won't shut down all the way. I don't know what the deal with that is but I guess it does not affect the driveability of the car.

As stated above, with either a cracked block or blown head gasket there would be high probability of water in the oil or oil in the water.

Double check the cooling system. Have you tried filling the cooling system, idling the car in the driveway and you under the hood/car looking for a water leak? If the water exits the overflow tank, then the cooling system is at fault.

I never thought of doing that but I will try it. (I'm female and I know nothing about cars).

To me, what does appear to be true is that a mazda dealer told me my miata needed a head gasket, which ended up not being the case. And a mercedes dealer has told me that my benz needs a head gasket which from the sounds of it, may not be the case either.

It seems to me that you can't trust dealers and all they want is your money.

Thanks everyone for your advice. I wish I would have found this site months ago, it would have saved me a few headaches.

Hi,
Park you car on a hill so that the front of the car is higher than the back. Remove the cap on the overflow cap and add water/antifreeze. When the engine comes up to temp check to see if the water/antifreeze in the tank goes down. If it does keep adding until you have a quarter full in the tank. If you see air bubbles coming out that would be great. Check around the water pump and hoses and the radiator for leaks. Check the wheel on the water pump and make sure it is working right,not wobbling.

If you want to ensure that you do not have a cracked block ( doesn,t sound as if you do) ensure the over flow is at a good level and let the engine set over night. If you do have a cracked block you will see a flim of oil in the overfow tank. There could be many more reasons for this problem but at least its a start.

Thanks for the tip. I might try that. What I really need to do is get the car into the mechanic I use that I trust and have him do a block test. I've been putting off doing that because the dealer said I needed a head gasket and a valve job and he gave me a price of $3,500. This was 2 years ago so I am sure they would charge me more now.

After reading the replies here it really does not sound like I need a head gasket. I don't have any oil floating around in the overflow tank and my engine oil is clean. I've been told if water was in there there would be a white color mixed in with the oil. Nothing like that is on my dip stick. I've been looking for a Mercedes board for awhile. I found a Miata board last year and discussed my problem with the guys on there and they said that the Mazda dealer was full of crap. It appers that the Mercedes dealer might be full of the same thing! I think some of these dealers know that a lot of women don't know a thing about their car. Which in my case, is true.

Let's get back to simple basics.

Check your viscous fan clutch.

Verify that the aux cooling fans (electric fans in front of the condenser/radiator, right behind the grill) turn on as the temp rises at a red light.

When the weather is warm, it is normal for the temp to rise when the car is stopped in traffic, especially with the AC on. As the temp rises the aux fans will turn on at high speed and cool it down, and the viscous fan clutch should engage the engine-driven fan. You can hear that fan make a sort of roaring noise as it moves the air through the radiator when you accelerate.

The coolant loss is not normal but based on what you've reported, to assume it is the head gasket is premature. It could simply be a hose. A cracked block is not likely.

Thanks for your response.

Boy, this is starting to sound a lot like the Miata board. The Mazda dealer had my Miata for 20 whole minutes and swore up and down I needed a head gasket. The guys on the Miata board said that those cars hardly ever need a head gasket and how did I run my car so hot that I needed one? Answer was - I didn't.

Based on all the replies here and also on what the transmission guy who worked on my other car said, I think my Mercedes needs a water pump. Oddly enough, that is one of the things the Mercedes dealer said I needed! A Water Pump, A Radiator and a Head Gasket.

Thanks again everyone.

PS Brewtoo - I live in Los Angeles and the temp gauge does the same thing no matter what time of day or time of year. If it is hot, or if it is raining. If I sit at a red light for more than say 5-10 seconds it goes from around 80 degrees up to the 100 mark and sometimes a little over that. As soon as I accelerate, it goes back down to the 80 degrees. Of course this whole head gasket thing has freaked me out a little and now I hardly ever drive the car. I put about 4,000 miles on it last year and I live in LA!

It sounds as if you know more than you think! At least when it comes to people feeding you a bunch of B.S. If the car had a cracked block or bad head gasket two years ago you have known it by now. Your problem doesn,t sound that bad, at least for a car with that much age. Please let us know how it comes out.

J.D.
Charlottesville, V.A.

Just curious, why a water pump? They are usually replaced on these cars because they leak (but they don't tend to leak as much coolant as you say you are losing and you said your leak is more toward the rear of the engine). Loss of pumping capacity is not likely.

Besides the coolant loss, everything you have reported is within the realm of normal.

Have a look at those heater hoses above the engine in the back on the driver's side. I saw one of those with a pinhole in it once and the coolant loss was significant.

This may very well turn out to be a simple problem.

You are asking wise questions. Listening to the dealer can be like asking a barber if you need a haircut!

I will. I am planning on having it towed into my mechanic in a week or so. I have to get a smog by July so I need to get whatever is wrong with it fixed.

I have done some homework. The Miata board I found was a bunch of guys who rip Miata's apart then rebuild them as race cars. So they did give me some of the ins and outs of things. But I took that as pertaining to a Miata, not a Mercedes. My Miata had entirely different symptoms than the Benz does. And the head gasket that the Mazda dealer diagnosed turned out to really be a sticky thermostat! $30. part and my mechanic installed it for free!

From my experiences:

Loss of coolant:
- Cracked coolant tank
- Hose going bad (in my case, the heater hose burst a few weeks ago on my W124...also in the shop for the head gasket btw.

Water pump failure:
- Weeping coolant leak near pump at first, complete purge of coolant on garage floor upon total failure.

Head Gasket:
- Worsening oil leak, actually BAD oil leak. Temps climb significantly while stopped, even in cold weather. Depending on engine, oil and coolant mix is also a symptom.

Cracked engine block:
- Oil/coolant loss, mix of both in coolant tank. Noiser engine. I find this to be a rare issue.

thanks again brewtoo. It does leak toward the back of the engine, I could tell when I moved it today. There was a bunch around the front of the car, but when I moved it I could tell by the trail of coolant that it stated at the back and went to the front (I was parked on a slight incline).

Something else I do notice when I put coolant in the overflow, if I look down at where the oil pan or whatever is there at the bottom of the engine, I can see a bunch of coolant laying there. Which makes me wonder how safe it is to even drive it around the block - is that stuff flamable?

I'm going to print all this stuff and take it into my mechanic when I tow it in. I did that from the stuff on the Miata board and it was helpful.

G-benz - I really don't have any oil leaks, or at least not anything major. I do keep an eye on it. I've only had to add oil to it once in the last 3 years and that was probably a year and a half ago and right now the dip stick is half way between full and empty.

I can't swear that I don't see any oil in the overflow, but it sure does not look like it. I just see the coolant level going down. But I don't drive the car enough. Just around the block once or twice 1 time a week. Maybe I should do it more than that then check it out? But the engine does not make any noises, and my mechanic said if I cracked my engine block he would think it would be making some kind of noise. Like a pinging sound or a clanging sound. A knocking type sound. I don't hear any noise like that.

By the coolant level going down. Last Sunday I filled it to the full level, and today it was probably 3/4 of that. And from last Sunday to today, all it did was sit (except for the drive around the block). When I moved my car is when I saw the trail of coolant from the back part of the engine (I would say the mid point of the car maybe), to the front of the car.

Just an FYI,
I had to replace the water pump on my 92 300E last week. All of the coolent that came out of the pump ended up near the back of the engine on the ground. From what you have stated I would think that the water pump would be the worst case sitution.

boy I wish I would have found this board before today. It appears I have been putting off getting my car fixed for nothing! Once I get it fixed I am going back to that Mercedes Dealer. I have the write up they gave me and it says head gasket, water pump, radiatior. By the way, I think it does say hoses. If I really don't need a head gasket they are going to hear it. This was 3 years ago that they gave me the diagnosis, and I have the exact same symptoms today as I did then. They have not gotten any worse. The only thing that has gotten worse is the amount of coolant that is leaking. I agree with what you said in an earlier post, if I really needed a head gasket I think the overall problems would be worse today.

At a minimum, a bad coolant leak
 

Get it fixed before you roast the engine at a stop light.

Could be hoses, radiator, water pump or all three. Likely not headgasket.

sounds to me from your description that you will need the following----------fan clutch-----probably radiator-------radiator cap----and depending on the colour of the plastic a new radiator reservoir.it's possible that the water pump is leaking[especially if the leaking happens as the engine is allowed to cool]----the almost instant heating up when you come to a stop suggests that the fan clutch is at fault.when warmed up you can probably turn off the engine but the fan will still be turning for a while?the radiators are made from aluminum and over the years the tubes will shrink so that at idle there is not enough flow-----but as soon as you hit the gas and speed up the temp comes back down.

david you pretty much have nailed it. Though I would not say the heating up is actually "instant". I would say that it happens at every red light if I am stopped there for more than 15-20 seconds, though I have never timed it. I do notice that the longer I drive the car the quicker it is to heat up at a light.

You are right about the fan still going after I shut off the engine. It does that occasionally, probably because I don't drive it that far anymore. I can say that one time I drove it without coolant was the first time I noticed the fan still going after I shut off the car. I was pretty worried when that happened.

I called Mr. MB Motors in Tarzana today and that is where I'm going to be towing the car to soon. Thanks for your input. Once I have a diagnosis I will come back and post it.

You never said at what temperature the temp guage is getting to.
How high does it gets?
On normal driving , you should see 80+
Stuck in traffic during the summer time, 100deg is not abnormal

I thought I did on the other page. It goes from about 80 to close to the 100 degree mark or just a little over. But then as soon as the traffic light goes green and I accelerate it goes right back down to 80. It probably does that in about 5 seconds or so.

I notice that the longer I drive the car, the quicker it is to heat up at a light. But the temp gauge always goes back down. I tested it a few weeks ago by letting it sit in park for awhile. After it got close to 100 I put the car in drive and drove down the block and the temp gauge went right back down to around 80

The only difference I have seen in the car since the 2 plus years the stupid dealer said I needed a head gasket is that it is loosing more coolant.

Water pump and fan clutch will fix you up.

The viscous fan clutch should engage the engine fan and cool the engine at idle -- it will go up to about 100C otherwise, where the electric fan comes on.

The water pump leak shows up about half way back, because the coolant runs down the engine along the head/block interface and drips off the rear corner of the oil pan sump, it drips onto the block.

The water pump will be expensive, it's a fiddly repair. However, a new pump and fan clutch should fix you right up.

Have them change the coolant to Zerex G-05 or MB coolant at the same time, do not use green antifreeze in that engine, it causes corrosion and will plug the radiator.

Don't be shocked if you also need a radiator eventually, too.

Peter

Finding a water leak is not very easy.
The best way is to pressurize the cooling system when the engine is cold. Any good shop must be able to do this.
The engine has to be really cold, best to let it cool down overnight and test in the morning.
Overheating at a stop sounds like a bad fan clutch, my 300SE behaved the same until I replaced the clutch. Also if you radiator has never been replaced it won’t be very effective any more after 16 years.

Rob

I've been using the green antifreeze, I guess I should stop using that?

I replaced my water pump in my Miata about 5 years ago and I know it cost some bucks. That thing failed at my office in the parking garage. I'm glad it did it there instead of on the freeway somewhere.

Thanks again everyone for all of your responses. I am glad I found this board, I have learned a great deal. I will post once I find out what is really wrong with my car, I am taking it to Mr. MB Motors. If I do not need a head gasket, and it does not sound like I do, the dealer that told me I did is going to be sorry they told me that. Even more sorry that they gave me something in writing saying that I needed that, a valve job, hoses, radiator and water pump. They even put in writing that I needed new spark plugs. I found that a bit interesting considering I got all new plugs 6 months before when I had a tune up at another shop.

Awww, really now. You know you'd be better off with all these things replaced. After all, the parts to be replaced are no longer brand new, right? So obviously, brand-new would be better. The dealer is probably just doing an extra-special job of keeping you safe.

:P

It is for me hard to say why the dealer made those recommendations, you did not give all the details; mileage, maintenance etc.

A temperature of 100 degrees is not serious overheating, if the cooling system is not leaking this should not be a problem. It indicates that some parts of the system are not as good as new. For a daily driver that has to endure summer heat in traffic jams I would fix it as soon as possible, but since you only use it once a week this may be different for you.

The water leak has to be fixed! If the water level drops below the head gasket it will overheat and blow out. Also the head my overheat an warp. These are much more expensive repairs than fixing a leak!! Have your cooling system pressurized (when really cold) and have the leak fixed. With the engine warm the water vaporizes making it hart to find the leak. With the engine running the fan will blow the water toward the back, making a failing water pump (front of the engine) look like it is coming from the rear..

If your car has 400K mls without a valve job the guides and seats may by worn, with 40K mls it would be very unlikely.

It is always best to make very clear to a Dealer/shop what you want to be repaired. If they recommend other repairs they must be able to explain why. It is up to you to follow their recommendations or not. You may be disappointed with the dealer if your car would have a problem shortly after being repaired and they did not warn you about it. With expensive repairs a second (or more) opinion is always a good idea.

Rob

I had the same problem you had years ago on my 300, everyone thought it was the head gasket including me, I was leaking coolant bad once it heated up, well It wasnt the headgasket althouht I did need one for the leaking oil, the coolant leak from the back turned out to be a hose that was located in the back of the engine a simple repair.

Thanks for the info Leon!

Rob - my car has about 88,500 miles on it. I bought it used about 4 years ago. I could tell that whoever owned it before me did not drive it much, the interior looked like it hardly had been sat in. I bought it from a place that sells very high end used cars, this one was pretty much the bottom of the barrell in their lot. But it has that old boxy shape that I like so I got it.

I got a tune up after I bought it, replaced the distributor cap, flushed the coolant and flushed the auto transmission, got an oil change. Considering gas prices over the last few years, I have not driven it much and mostly drive my other car. I bought it at around 82,000 miles. Did a car fax check on it. I had my regular mechanic look at it before I got it. I'm driving it once a week so it has a chance to get out and 'exercise'.

I did have to replace the shocks about 2 years ago, found out they were the originals, so I think it is safe to say that maybe everything in there is original. The car only had one owner prior to me and it was an older couple who said that was their 'sunday driving' car. Which probably explains why the low mileage for a car in Los Angeles.

I've got a 93 Miata that I bought new, I always get it serviced on time and right now there is nothing wrong with it.

Just curious. What was the reason for replacing the shocks?

I was getting abnormal wear on my tires, I had some high spots and low spots. It seemed like the front end went down a bit when I would brake sometimes. Plus I think they were leaking.

I think it was only the front ones that were bad, but it was recommended that I replace both front and rear at the same time so I did. I got the ones they took off the car and they were the original shocks, about 14 years old.

It was either the shocks or struts. I don't know the difference between one or the other or if my car has shocks, struts, or both.

David - question for you. I went down and started my car tonight, with all the info I have gotten from this board on my mind. I did notice that when I started it, it sounded like a fan or something was running. I also recall that I had not heard that before until the time I took the car out when apparently there was no coolant in it and the temp gauge went up to the red for maybe a few seconds (I shut it off pretty quickly and let it sit for a few mintues. I was not far from home, maybe 3-4 blocks). It seems like since then when I start the car I hear this fan running. Would that be the fan clutch that you are refering to above?

That fan sound is the only thing I hear. I don't hear any noises other than that coming from my engine.

no,that would be the aux fan[s].apparently the temp switch[blue double pin] has gone bad and the circuit is doing what it is supposed to do when that happens i.e. run the fans at all times.

if the temp switch is bad, could that be another reason why the temp gauge goes up so much at a red light? I know that is not going to be the cause of the coolant leak!

Thanks.

no that is a diff temp switch than the one used to operate the gauge.

Thanks David. I'm sure learning alot on this forum!

you're welcome.

I just found the write up from the dealer. This was written up on Dec 17, 2004 which was obviously awhile ago. I see the head gasket and valve job on there and a couple people on here have said that if I needed a head gasket 2 years ago I would really know by now if I needed one. I don't know much about cars, but I tend to agree with those statements.

The write up also says water pump (has seepage), radiator, coolant bypass hose. (I think that is what the real problem with the car is).

I'm doing this post because it also says steering shock and p/s pump reseal kit. Does that mean they are trying to say my power steering pump is leaking? Can you guys tell me where I can check the fluid level for that? I know where it is on my Miata but I don't know where it is on my Benz. I read the recent post on here about leaking power steering fluid and if the result of that is having problems steering, I don't seem to have any problems steering my car when I drive it around the block.

It also says 2 Motor Mounts, 1 Trans Mount, 1 belt tensioner + shock. I don't know if they are talking about my shocks for my tires, but I had those replaced before I took the car in there.

Oddly enough they also say I need 6 spark plugs and this was Dec 2004. I replaced all spark plugs in Oct 2004 I really wonder sometimes if they ever even looked at my car completely.

Any help on this would be appreciated. It's probably going to be a few more weeks before I tow it in. I have a small hole in my exhaust manifold on my Miata and I need to get that fixed first since that is what I am mainly driving.

300se Coolant Lose
 

Check your monovalve. The thing by the battery that has hoses going to it and sometimes that plastic case cracks and u could be loosing coolant that way. This is behind the motor up on the firewall it has two wires going to the top of it. Also check under the dash on the passenger's side for the floor board to be wet you might have a possibly leaking heater evaporator. Whatever it is should be simple! GOOD LUCK and please keep us all posted!

Well everyone, I am towing it in tomorrow to Mr. MB Motors. I should know soon what the problems are and I will let you know.

Thanks again for everyones help on here, I appreciate it! :)

I had my car towed in on a flat bed and when the driver took my car off of it there was coolant all over the truck bed.

I explained the whole thing to Enrique and he took a quick look under the hood and right away said I needed a water pump, he could see where it was leaking. He's going to replace that, then do a pressure test and tell me what is what.

I asked him about the head gasket and he pulled out the oil dip stick, looked at it, shook his head no and that was that!

Best of luck!

DIAGNOSIS:

Water pump. After Enrique put that in he did a pressure test and he said I didn't have any leaks. He told me he let my car run for a half hour and it did not go above 80 degrees.

I also needed a belt tensioner and shock. I have no idea what that is but he put that in.

So, out of the 10 items on the list the Mercedes dealer gave me in Dec 2004, I only needed 2 items. I will never go back to that place again. Imagine - they wanted to charge me $3,500. for a head gasket and valve job I don't even need!

I also needed front brakes, oil change, and whatever it is my A/C uses to run. My sliding sunroof is off the track, so he ordered the parts for that and should have them in a few days.

The needle on my dash for the RPM's does not work, so I am going to have him check that out. That happened to my Miata once. (it was the speedometer on that one and I replaced the cable). I am guessing it is the same senario here.

So, those are the problems in my 16 year old car. I've got no complaints!

Thanks again everyone - most everyone was right on the money. Enrique said my radiator is working perfectly and no reason to change it now.

If somebody could tell me what a belt tensioner plus shock is I would appreciate it. I didn't ask Enrique when he called me this afternoon, I could tell he was busy. I'm sure glad I found this guy. He has to be the most honest car mechanic I've met!

The belt tensioner keeps the serpentine (aka fan) belt tight. It is a legitimate maintenance item that does have a limited life.

The tach is electric and has no cable.

Good job dodging the sharks!

Yep, way to stay with it. The waterpump.
This topic was worked over well. Nice to see.
If you leave it up to the dealer, his primary
objective is to bill, bill, bill. He wants to make you happy,
but he has a lot of people to pay. If you had left it up to him,
sure, he would have replaced the waterpump, and also every other
superfluous system part he could squeeze into the work order.
Have seldeom seen a dealer that didn't. They have a lot more
overhead than your typical independent mechanic. They
almost don't have a choice but to write big work orders,
and a MB dealer, they figure you've got $ growing
out of your ears.

A pet tip: Make sure your dog doesn't lap up any coolant.
It's sweet, and they like it, and it will kill them.
Some folks even use it as a dog/coyote poison.

Yes the dealer did make me mad, I'm just glad I found this board.

So I had a Mazda dealer tell me I needed a head gasket on my Miata and a Mercedes dealer tell me I need a head gasket and a valve job on my Mercedes. Neither car needed those things!!!!! Amazing..........

Oh - I convinced Enrique to give me a new radiator even though he said I did not need one. I felt if I got a new water pump and thermostat and then had a 16 year old radiator, that probably was not the smartest thing. Even if the radiator was working fine at the moment. It's supposed to be a hot summer.

Thanks again EVERYONE!!