300d New thermostat, water pump = cold radiator and overheating
 

edit: 1987 300d
The only thing I can imagine is that the radiator is clogged. Also, from working on bimmers, I'm used to a coolant bleeder valve but I don't see one on this car (maybe i haven't looked hard enough). Is it possible that i have air in my system keeping coolant from flowing properly? If so, how do i get it out?

the metal hose above your thermostat that goes over to the expansion tank is the bleeder.
you could also have a stuck closed thermostat. did you test it? is is an O.E. stat or a "same as"?
call Roy at the "buy parts" button. he has a nice long list of updated thermostats for this car. get the latest and greatest.

Not to doubt you but did you get the orientation of the tstat correct?

My thought as well. Is the thermostat in backwards? Don't laugh (or ask) how I know it can be done......

It would be useful if you could tell us a little more.
When does the car overheat?
What is the condition of the coolant?
Have you done any recent work on the cooling system?

There are many good threads on cooling system problems, even diagrams on the correct installation of a thermostat.

Try this link http://www.dieselgiant.com/thermostatreplacementandmodif.htm

Yes it is an OE thermostat. I installed it with the longer, protruding portion facing the engine. I think that was the only way it would fit.

There's really not much to it. Once you start the car, the temperature increases when idling (faster when driving) and within a few minutes the temp needle creeps all the way up.

When I stop the car and open the hood the radiator is cold to the touch. The top hose is hot but not really too pressurized. The bottom hose is hot but squishy.

I was thinking a cracked head or gasket but i have no white smoke at all and there is no coolant in the oil.

it sounds like you did not get water into the block.
be sure and fill the head with the upper hose, and possibly disconnect the heater hose, and fill from there.
actually, I'm not familiar with the 603 yet. (I'm learning quickly) but be SURE water is exiting the small upper hose that connects to the expansion tank.

Thanks, I'll definitely take your advice. Has anyone had a radiator actually clog? I've read threads alluding to it but I've never experienced that in the past. I've only seen them leak.

oh sure. I've seen tons of clogged radiators.
morons that start out with a leak, fill with tap water, and keep filling and driving this way. rust, and lime from the tap water really does a number on aluminum and cast iron.
also letting the coolant expire and driving for years on old coolant will do the same thing.
I've seen shop rags in the radiator too... can't really blame the radiator on that one...

Ok, one more dumb question: What do you think of using CLR (calcium lime rust) to flush out the radiator? I think they sell it in walmart. If it doesn't hurt aluminum it seems like a win.

I'd only use the recommended citric flush myself. no.
and I'd only use it if the parts determined to have corrosion and damage. and I'd be prepared to replace the radiator if I had to use it.
pull the block plug, and see what comes out. look into the radiator and see if the tubes are plugged or corroded.
then flush normally, and see if the gunk and corrosion is still present. only then would I use the citric acid flush on this car.
also pull and inspect the water pump. the vanes could have been corroded out.

x2 on this.

You can make an acid flush using vinigar, citric flush, CLR, glacial acidic acid, anything I suppose if you understand pH and alkali metals (aluminum et al) but you will eat metal as you eat sediment, no way around it. If the metal is already thin (original with miles), it might make it too thin.

Antother thing that can clog radiators: mixing Dexcool with regular glycol-based coolant, or over-use of "stop-leak" products. Take both hoses off of the radiator, flush with water, if it comes out of the other end (bottom to top is best) then it's not clogged.

heh, keep the expansion tank cap on for this test...:rolleyes:

Ok, now I'm more confused.

I removed the radiator and flushed it well with the hose. Flow seemed normal, no chunks of anything, clear water coming out. looking inside through the neck, clean with no corrosion. I think it's safe to assume it is not blocked.

I fill up using the above method, filling through the top hose so the block is full (i assume), filling from the top neck of the radiator until full and then topping off the expansion tank.

After i hook it back up I took it for a ride only long enough for the temp gauge to go to the hash mark above 80. I pull over and feel around the radiator. The top hose is very hot as well as the radiator within a 6" radius of the top hose neck. The top hose seems under a lot of pressure and hard to the touch. The rest of the radiator is ice cold. The lower hose is cold and slightly less pressurized than the top.

Does the coolant flow bottom to top or top to bottom?

Coolant flows top to bottom.

We're back to "is thermostat installed correctly? Is thermostat opening at correct temp?"

Have you measured radiator temp with a thermometer to confirm temp? What caused you to change the thermostat to begin with?

I suspect that the Walmart automotive department sells some stuff specifically designed for use in automobiles. And if Walmart doesn't have it, any auto parts store worth its salt will.

Remove the thermostat and do a test drive.

Considering that the pump is new, that might not be all that probable.

On the subject of the pump, however, it is possible to get a pump (especially an overhauled pump) that has vanes oriented in the wrong direction. (That happens quite often with some domestic engines that have different drive belt configurations in different vehicles.) Incorrect belt routing can also cause a water pump to rotate backwards in some applications.

Only a few components to deal with :
Radiator
Thermostat
Water pump
Block

With a hot upper and cold lower, indicating zero flow, its looking like either
a bad thermostat or a bad water pump.

I replaced the thermostat because the radiator was cold. I'm sure it's in correctly and I would be surprised if the old one was bad as well as the new one. I would like to take it out completely for testing purposes but I don't think there is a way without it leaking. I suppose I could gut out an old one. It seems to me that the pump may be at fault. Im going to try to find a picture of a new one and compare vanes.

I'm thinking pump. Cavitation pitting can destroy the pump over years/miles of incorrect or inadequate coolant.

To test the thermostat, heat some water on the stove with the thermostat in it, observe the temperature where it opens with a thermometer.

IIRC the cooling system does not circulate correctly without the thermostat in the housing, I might be thinking of the wrong engine though.

If the title of the thread is any indication, that's not the problem.

I pulled the guts out of an old one, and stuck it in there with the oring in place to flush and clean everything.
do you still have the old pump?

Just a quick update.

I tested the old thermostat in a pan on the stove. It pops open at around 85C, definitely not 80C. I don't think this would cause the type of overheating i'm seeing but I gut it anyway and install.

Around town the temp now hovers around 80 maybe a little more. When you stop the car the radiator is only moderately warm all over. Taking the car on the highway things change. Temp starts to go way up after about 5 minutes at 65mph. If I put it in neutral for 5 or 10 seconds and then drop back into drive the temp goes way down.

So it looks like the radiator is fine as well as the thermostat. All signs point to the water pump or some type of clog or crack in the water pump housing. (I would like to hold off on a cracked head diagnosis until the end).

It seems very strange though. The water pump is new! And looking at pictures it doesn't look physically possible that the vanes could be put on backwards. Maybe it's a pump from an older model that had a reversed coolant flow?

I don't have the old pump. I wish I had

pull it and take a picture. we'll compare it to ones we have.
could have gotten a gasser pump that spins the wrong way for your motor.

Ok, here's a picture of the water pump. Looks new and spins freely. There's a little surface corrosion because I've been using water to test with. Other than that it looks fine. I don't see how the impeller could have been put on wrong. Is this correct?

check your belt routing, just to be sure.

It's not about whether the impeller was installed correctly; it's about whether it's the correct impeller was installed.

That said, the impeller vane orientation does appear to be correct.

The belt routing was the first thing checked.

Well, if the vanes are oriented correctly and the pump is spinning, water should be flowing. But it's not. With the pump and housing off of the engine the next step will be to flush the block.

At what point should I stick a rag in the tank and light the car on fire?

I would also check the radiator for debris in the fins. My 85 300TD has been running hot (up around 100 deg.) with similar symptoms. My radiator was cold in the center and hot at the edges. I took the radiator out and power washed it, blowing the fins out back to front until it drained clear. A new genuine T-stat and my temps are now steady just above the 80 mark and my radiator is hot all over.

Soft Red,

What is the latest? I have the EXACT same issue with my 98 W210. It has a new RAD, and OEM T-Stat.

It is really strange... Up to 60MPH it sits around 90C... When I go over 70 it will hover around 100 and shake a bit then shoot up to 120.

Sometimes it comes back down.. sometimes not.

Rad is warm/hot, hoses are hot and firm...

I went to the stealership and got a temp sensor since it seems to be all over the place.

If that doesnt work Im pulling all the hoses off, pull out the water pump and take a look..

Then flush the block..

After that I may resort to your solution.. rag with gas haning out of the tank and a match.. JUST KIDDING... LOVE the car..

This is just a new "ISSUE" I havent had to deal with yet and frustrating..

Im hoping its the sensor since I have NO indications the car is really running that hot.

keep us posted and Ill do the same.:D

On the W123 90C is where it opens to the radiator and shuts off the bypass. Probably the same/similar for your engine?

Not much of an update, I haven't gotten the car back together yet. I'm just waiting on the housing gasket. My efforts at cutting my own out of gasket material with a pair of kid's scissors haven't turned out too well.

One thing worth mentioning: when the water pump was last installed, the gasket was "sealed" with that translucent blue silicone crap that people love to use. An excess was squeezed out into the cavity of the pump housing and may or may not have caused problems. I cleaned up the area, degreased the passenger side of the engine (just because), flushed out the block (without anything really getting flushed out), and am going to put it all back together (correctly) and hope for the best.

If the hose is cold then you have no flow and should look elsewhere, not the radiator. That should flow some, as you have done the hose in the radiator test.

Although I think now you are having some flow as from some of your latest posts. Your radiator was warm all over and temps were around 80 around town - light driving.

I had tried flushing my system after having some high temp problems. I was fine around town for a while, but rising under load. I tried thermostats to no avail. I finally took the radiator to a radiator shop and they flushed it out. They had to boil it and backflush it three times before it came out clean. It cost me less than $60 and the car has never run better. The temp is always within 1 needle width of 80* summer or winter, AC on or not.

I haven't seen your gasket however, if it is made from a sheet of regular gasket material: Use a ball peen hammer to make the gasket. Simply lay the gasket material on the housing and tap the material with the ball side until the housing comes through. Much quicker than waiting on the pre-made gasket.

Just a quick update:

Everything is back in and re-installed. Same problem, still overheating on the highway. I took the radiator to a shop that specializes in radiator repair and he ran a flow rate test. According to his test it only flows 10 gpm vs. the 39 gpm which it should according to it's dimensions. Case closed, the radiator is clogged. So it turns out that crouching in my driveway flushing with a garden hose is not the best way to test your radiator. Go figure.

So I just installed a brand new radiator and took it for a drive. SAME EXACT PROBLEM. top and bottom hoses are hot and slightly firm. The radiator is warm on the extreme ends and cold in the middle. How is it possible to have no flow with a new radiator, water pump, and no thermostat?

With no thermostat the bypass is open.

Can you please explain some more for a merc newbie? How does the bypass work?

The bypass circulates the water out of the engine and right back in. This is before you get to the radiator. While some warm water will push out to the radiator it is entirely possible that the outlet of the radiator is cool. I still think its a bad tstat.

Your symptoms indicate that there is not enough coolant inside the block to open up the thermostat. I had the same exact problem years ago and some cars are just too stubborn to burp, and my car is one of them, but it's an '85 with a 617. I'm not familiar with an '87 but filling the system at the heater hose closest to the firewall with the car's nose up did the trick for me after several attempts.
Good luck!

I'm going to give it a try. Thanks

Put the thermostat back in and burp it.

I tend to agree. I think you have an air bubble somewhere in the system preventing proper flow (most likely in the block I'm thinking) put a NEW thermostat in and try burping it.

Ok, I've tried all of the above. All the are bubbles are out and still no dice. It looks like I have the dreaded cracked head based on other research. So, the car is up for sale as a whole to start with. Thanks for all the good advice.

http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/282551-1987-300d-whole-car-parts-ct-%24800-post2521938.html#post2521938

Sorry it has gotten you to this point, but I clearly understand your frustration.

I have been driving my 240D without a thermostat almost 10 years.

About 10 years ago I bought a complete engine from the dealer and replaced my old motor on my 240D 77. Shortly thereafter a big chunk of rust that was stuck somewhere in the remanufactured motor came loose and filled the cooling system, the coolant was dark brown in color. At any rate the mechanic suggested that I replace the radiator, change the thermostat and clean up the mess. It was all done except that the new thermostat refused to open no matter what, they burped and did all the tricks, nothing helped, I finally told the shop to remove the thermostat, it all started to work fine without one.

It has been almost ten years without a thermostat and since I live in Houston where summers last 9 months not having a thermostat keeps the engine a bit cooler. In the winters I put a little cardboard in front of the radiator to help with the heat, everything works just fine.

Vahe

A whole parts car??? :splat:

Was there a "smoking gun" that brought you to this conclusion? Since joining this forum, it seems like there have been several threads with engines getting hot and virtually every part associated with cooling is replaced, yet the problem goes unsolved. If I had the money, I'd buy it and replace the head, BECAUSE NOW, I JUST WANNA KNOW!!! :vbac47679