Radiator. Gauge, or block?
 

Here's my situation:

After doing an overhaul of my cooling system (changing water pump, thermostat, and extensively flushing block and radiator) my temperature rose to a consistent 100C, either at highway speeds or city driving, but with no needle bouncing or erratic behavior.

The only problem with this is that the block is not ridiculously hot to the touch, the radiator is barely warm to the touch except at the top black plastic cover (where it is very hot), and the coolant in the reservoir is lukewarm at best.

Furthermore I can remove the cap of the reservoir when it is purportedly 100C in the system without any pressure escaping, much less heat.

--The hose connecting the block to the radiator at the top is very hot, as is the top of the radiator.--

I drained the radiator again, suspecting a slight blockage in there, flushed it, refilled, and this time bled the system. But this only dropped it to about 95C when driving at city speed and 98C at idle. Probably 100C at highway still.

I don't suspect the gauge since it is behaving smoothly, so there must be some blockage in the system, right? I really don't want to have to replace the radiator, it seemed to flow fine when I flushed it, could there be a blockage in the engine?

I need to fix this since this is my daily driver car, and I don't want to damage the engine with this high heat. Thanks everyone who helps me out with this car, I wouldn't be able to do it myself without y'all.

hell mine doesn't even quite get to 80 c on the highway....................but then I just got it working that well yesterday.................

Also...
 

I forgot to add:

I bled the system by starting the engine cold with the reservoir cap off and running it at operating temp. a while, let me know if this is wrong, it's what I read on some threads. The car is a 300cd turbo. I'd love it to be an air pocket.

I don't think the aux. fan is coming on at 100C, but I'd have to check further to be sure. I know at least it was working some 6months ago.

Will 100C (if it is in fact at that temp) hurt the engine, or is that within the acceptable range for very temporarily?

On my car, 120 C is redline. During the hot summer months when I'm doing 75 - 80mph on the interstate, my temp stays around 100 C. I've never had any problems. However, what I personally consider normal operating temp. on my paticualr vehicle is a little bit over the 80 C. mark. Cheers.

I am having a similar problem. I just replaced the water pump, thermosat, belts and hoses. Now my top hose and top of the radiator are hot, but the top hose is not hard as it was before and I can remove the radiator cap right away. The bottom hose is noticably cooler than the top, which also is not hard. I was wondering if I installed my thermostat backwards? Maybe this is now normal? Temps hold consistently at 81-82.

I highly recommend you perform the following procedure. If it works, it will save you from purchasing a new radiator:

Pull the radiator out of the vehicle. I know, it's a PITA, but, it's worth it.

Hold the radiator up to the sun. Look through the fins. See all that crap?

You mission, should you decide to accept it, is to remove every bit of that crap which is blocking airflow in a big way.

Use compressed air, a chemical cleaner that foams, and a whole lot of patience and repetitive cleansings from the rear side of the radiator to attempt to flush as much of that crap out as you can. It takes a good two hours and it won't be perfect, but, you'll drop the temperatures at least 5°C. and maybe even 10°C. if the radiator is quite bad.

Unfortunately, there is no tool that I could find that can be stuck into the fins to clean them. I think even pipe cleaners are a problem, but, I haven't tried it.

If this does not solve the issue, then the radiator is partially plugged internally and a new radiator is probably going to be required to significantly drop the temps.

Brian, I don't want to hijak 83's thread, but we both just did similar work, and we both now have similar results. I am running 20 degrees cooler than him, however. But my concern is that I never saw the soft upper hose before and being able to remove the radiator cap right away.
Th only thing I can figure is I changed something when I put everything back together. Well, you can't put in the water pump incorrectly, nor the fan or belts or hoses. The only thing I can think of is maybe I wasn't paying attention and put the thermostat in backwards. What symptoms would a backwards thermostat cause?
I have another gasket so I am tempted to check it out.
Your thoughts?

I would not remove the thermostat. If you had it backwards, the temps would climb well over 81-82°C.

My guess is that the new thermostat allows the engine to run a bit cooler than the previous one and, therefore, pressure has not built up in the system.

Take it out for a good run uphill when the ambient temperature is above 80°F. I'll bet it develops some pressure under those conditions.

Take PEH advice on this one: If it ain't broke, don't fix it. ;)

An interesting point is raised here. Shouldn't the side of the thermostat with the spring be facing towards the block entrance so that it is pushed open as the coolant heats/pressurizes?

Would a backwards thermo cause a temp like 100, like mine? Also I could try putting in a different thermo if that one is bad, I actually happen to have one, but the one in now is a behr, not likely defective.

I take it if the thermostat is not the problem I will either have to clean or get a new radiator?

Alright, I'll leave it alone.

The thing is my old thermostat ran at around 84 or so and the upper hose was always hard and the system was pressurized.

Maybe it is running cooler because I did repeated flush's after using Prestone Flush? The PO apparently hadn't touched the coolant in years as it was rust water that came out initially. Probably why the water pump started weeping. Man, whoever replaced that pump before used gobs of black silicone and a "made in Japan" water pump with odd looking fins - they weren't the cast ones that the German manufacturers use. The only reason I replaced the thermostat was I was in there already doing the water pump etc. and decided to do it as a PM.

So, the upper and lower hoses being soft to the touch, and the lower one feeling considerably cooler than the upper one is nothing to worry about? Just being over anal about my old benz's I guess :D Man, my kids think I'm nuts messing with these old things all the time when I have "nice cars" sitting on the sidelines ;)

The lower hose should be cooler than the upper hose. If it's not, the radiator is not doing a very good job!

That's the correct orientation, but not for the reason stated.

I believe that the aux fan is energized on the basis of refrigerant temp in the a/c system, not by engine coolant temp.

But this only dropped it to about 95C when driving at city speed and 98C at idle. Pro
 

"But this only dropped it to about 95C when driving at city speed and 98C at idle. Probably 100C at highway still".
Something is wrong with the above scenario.
That engine should not run 100 C unless its driven up a steep hill, on a hot day in the desert.
I suspect you have installed a bad thermostat. There has been reports on this happening with new thermostats, Bosch or Behr? I don't recall but you can search the subject and read it.
I would not drive an OM617 that acted that way unless I used an infrared thermometer to prove my gauge reading was incorrect! :eek: :eek:

"I bled the system by starting the engine cold with the reservoir cap off and running it at operating temp. a while, let me know if this is wrong, it's what I read on some threads. The car is a 300cd turbo. I'd love it to be an air pocket."
Did you back-fill the system using the port on the head as the inlet?
You might just have a bad thermostat and no water in the head (aka air pocket)
Did you measure how much water you put into the system? I add approx. 1.75 gallons. (one gal antifreeze and the rest purified water) About 1/2 gal remains in the heater and connecting pipes.

I recently did similar work on my 95 E300D, and ended-up with similar symptoms. In my case it turned out to be trapped air in the system. Took close to 300 Miles, over an 6 day period to get rids of it. Coincidentally, my 1 year old Rad cap gave-up at the same time, would not keep pressure.

Try the following: 1) squeeze the top of the radiator hose when its hot. Should be pressurized. If not than its the cap. 2) Squeeze it when its stone cold. Is it soft and spongy, do you feel air bubbles?

So if your problem is trapped air, be patient, it will escape on its own.

Phil

If I am not mistaken the key to all these problems are to jack up the car in the front as high as you can and bleed the system that way...Had the same problem and after the previous procedure it is fine....

The temperature no longer hits 100C, having flushed the radiator again, but I will try putting my other thermostat. Keep you posted on that.
While I'm at it I think I'll also put in a new radiator since the one currently in it was left for a while with old antifreeze in it and not driven. I'm guessing there's some rust on the inside.

When you say to back fill it through the port on the head, you are referring to the top port directly to the front left (as looking at the engine from the front of the car) of the valve cover? The one that the top radiator hose plugs into?

If so, then, yes, this was filled totally. I did not think to measure the amount of coolant I put in, but I will certainly do this when I change the thermostat.

Why would you jack up the car? The return line from the top of the radiator to the reservoir is already the high point of the cooling system and therefore the air is constantly escaping through there and will release when the cap is taken off. What procedure are you referring to?

Simple....take a look at where the thermostat housing is....take a look at where the top of the head is.........thats where the air pocket is....not the top of the radiator. that helps force th eair buble forward and out of the head.....

AN incorrectly installed thermostat will cause overheating - not sure that it would stop at 100'C though?

Remove the thermostat - check it's orientation when removing it -was it installed correctly?
Test the thermostat in a saucepan of water on stove, 100'C thermometer, note temperature thermostat starts to open,
Check your other thermostat too.
Reinstall the better thermostat in the correct orientation.
Report to us the results of your investigation and test drive engine temperatures too.

Why did I ever FIX the cooling system?!
 

Ironically, I installed the new thermostat and water pump to get engine temp up, my old thermo was broken open all the time. Well, I got what I wanted right?

I put in the other thermostat correctly...the old one was in correctly after all...and no result. I tried jacking up the front end as high as it would go and running the car for 10 minutes with the reservoir cap off, and still no luck. Temp the same, even a little higher since the air pockets haven't cleared out yet this latest drain and refill of the system.

So probably my radiator then? Here's what puzzles me:
Lower radiator hose to thermostat housing=cool, which means radiator is working
Upper radiator hose, block to radiator=very hot, which also seems right.
Thermostat housing=hot, right.
Thermostat to block connection=very hot, which all seems right.
Where is my problem? Just not enough flow through the radiator maybe?

Also, could someone explain the best bleeding procedure? I've read to jack the car up, to run it with the res. cap off, to do nothing and wait for it to go out, and on and on. Are there any bolts or plugs I have to remove to do it? What is the best way? I feel like maybe I'm missing something on this part and maybe an air pocket is plaguing me.

I have had good success by using the upper radiator hose to refill the cooling system. I disconnect the hose at the radiator, bend it back and up, and add the water/antifreeze through the hose instead of the coolant reservoir. When I filled at the reservoir, I always had a problem with trapped air. But it always seemed to "burp" pretty quickly, at which time the reservoir would empty itself. So the fact that your problem has lasted so long causes me to suspect that perhaps your thermostat is bad. (I am assuming that your reservoir is still at the proper level.)

The reservoir is slightly above the recommended fill level.

It can't be my thermostat, because I have put in two different, new thermostats, both with the exact same results.

My suspicion is the radiator (not a high enough flow rate through it) and so I will replace that this weekend. Then I'll refill with the exact right mixture coolant/antifreeze, in the right amount, fill with the best procedure (I did use your method of the top hose as that does work well), and hope for the best.

Did you install a genuine Mercedes water pump or some other version?

It was not a MBZ part, but it was a german pump (I forget what brand, I could tell you if you really want to know), and it had the metal fins and everything---not like the crappy ones with the plastic fins---appeared identical to pump already installed which was original equipment.

The reason that I asked is that there have been a number of reports on the forum regarding poor performance of non-OE water pumps. The problems had to do with the impeller design, which resulted in poor coolant flow.
It's difficult to believe that your problem is being caused by the radiator, considering that the engine was running too cool before. That demonstrated the radiators cooling ability. It doesn't make sense that it would loose that ability all of a sudden.

What brand of non-OE pumps showed problems. Do you know? I always use LASO brand pumps. I agree with tangofox007 about radiator - it would not suddenly stop working properly (unless you used stop leak or something awful in the system ;)
I once had a suspect radiator so I took out the thermostat and the engine took a long time to warm up (of course!) and ran cool as a cucumber even with A/C on and a hot day it never approached 100 deg C. Installed a new thermostat and everything was fine, so the old thermostat was sticking or not opening fully when it should have. Try that as a test, it's easier (and cheaper) than a new radiator! PS you can reuse the gasket if its new just don't tear it taking it off though.

I don't know.

I've been thinking about this again.

If the engine was running too cool prior to all of this work, then the radiator cannot be the culprit. The radiator does not go bad overnight.

I am assuming that you had no cooling problems and the engine would never get up to 100°C. prior to all this work, correct?

And, you have installed two different thermostats, with the same results. So, this basically rules them out.

The only other items are the water pump and the fill procedure.

These engines can get some air in them and I have also found that it's best to fill the engine via the upper radiator hose after you disconnect it from the radiator.

Then, take it out for a drive. See where the temperature stabilizes. It may climb up to 100°C. and then settle back to 90°C. after more air is returned to the tank. Make sure the heat is on full during the drive.

If you still cannot get it down near 90°C., then you have two possibilites:

1) The pump is not up to par (very doubtful).

2) The gauge is not reading correctly.

To prove #2, you would need one of those infrared temperature probes to check the temperature of the coolant in the upper hose. If you read 90°C., then you know it's either the gauge or the sending unit.

Thanks. I will try using one of the IR thermometers if I can get my hands on one (would this be at a hardware store or an auto store?).

Also will report back if the temperature happens to drop to correct level as air leaves the system.

I may try the thermostat test, but the chances of two different thermostats both being equally bad is almost nil.

As far as the radiator, yes, I know it didn't go bad in such a short time, but it can't hurt to put in a new one because my old one does drain some particulate matter each time I drain/flush the system, so I'd like to do it preventatively before it gets plugged up or plugs up the block.

I am assuming that you had your heater set to full heat when you were trying to purge your system of air. If not than air, could still be trapped in your heating system.

Also, if you set your heater controls to full heat, do you get hot air out of the ducts? When your engine is at operating temperature, and depending on your ambient temperature at the time, the air temperature coming out of the ducts should be somewhere between 100F - 125F (approximately).


Phil

I went through all of this crap last year when I started running the A/C. I had an infrared thermometer and used that 1st to determine whether the guage was reading correctly. It was close enough. I did the standard internal flushing with no results. I finally did pull the radiator and did the look through test and it was very clogged. I used my power washer and cleaned the radiator fins in about 15 minutes. I also cleaned the fins on the a/c condensor, but you need to be very careful here as the fins are thinner and can bend under power washer pressure. Problem fixed.

Those fins on the radiator are quite thin and delicate. How did you operate the power washer to prevent bending them?

I presume that you placed the nozzle directly against the fins for maximum effect. The velocity of the water in this situation would be of a concern. Please provide more details of the pressure in the machine and the technique utilized.

This is an electric power washer (Wal-Mart special--1300 psi IIRC) and I used an adjustable nozzle with a fan shaped output. I sprayed directly up against the radiator fins with no damage and no problem. I sprayed de-greaser on the fins before I power washed. I used the same washer for the A/C condenser but held the nozzle about a foot from the fins. Again, no damage and no problem.

Before I knew better, I bent the fins on an a/c condenser on a jeep with a higher pressure washer one time.

Excellent. I new there was something special about that setup. The 1300 psi is low enough that it won't do any damage.

Did you check it by holding up to the sun when finished? How clean does it get?

An attempt to dissolve internal deposits can be made with citric acid. It will dissolve the white calcium deposits. Another post dealt with this topic today. A good radiator shop can also "rod" the tubes to mechancially remove heavy deposits then solder the top tank back in place. That's the nice thing about not having one of those plastic radiators Mercedes beancounters are so fond of you can do some repair....

I find that the power washers at a DIY Car Wash works good for cleaning the external fins.

Heating sys. may be problem!
 

I did not run the heat when I purged the system! It hasn't been blowing hot air for a long time when the system was running too cold, and now it must be because there is no water in the pipes! I didn't bother running it because I didn't think it was working.

I'll go out and try the purge now with the heat on and maybe it will have some effect. (fingers crossed....PLEASE FIX IT!)

"No heat" is symptomatic of air in the system. It should start blowing hot air when it "burps."

Heat Purge Unsuccessful...
 

Last night when I did the purge with heat on, heat began coming out of the vents at a certain point, and the temp dropped to 85-90C, however the coolant level in the reservoir did not drop.

Today I attempted again and heat did not come out until I was almost finished, then stopped coming out when I switched to a different blowing pattern on the climate control panel. Again, the coolant reservoir level did not drop.

I'm almost positive there is air in the system, but it does not seem to want to come out. I suppose this is what's causing my wacky heating. I don't really want to do a complete flush and refill, at least not until I have my radiator since that requires a flush/refill anyways.

Also...
 

The coolant in the reservoir is not hot at all when I open it, and the top radiator hose is spongy and I can hear air moving in the system when I squeeze the hose, but cannot get it out.

Go back and re-read my comments in post #16. The air WILL come out on its own without you doing anything special, exept driving with the heater on at Max heat.

Be patient.

Phil

Did you take it out for a drive?

If not, you need to do this if you expect the water pump to force the air back to the tank. Even after one drive, the process is not complete. It sometimes takes several hundred miles to fully get all the air out. The expansion tank level will always be a tad low, every time you check it. Then, finally, it will stabilize.

Strange...
 

The temp. may be dropping slightly as the air leaves the system. I'll keep my fingers crossed, I think running the heat helps. However, the heat is working strangely.

When the car is running, it sometimes blow warm air when on the control for blowing out the 4 vents, but mostly cold air, engine temp does not drop.

When I turn the car off to just electrical, no engine, it blows very hot air at me and does drop the engine temp, unlike when the car is running. Why is this?

Also, when I press the control labeled "EC" it blows very hot air at me whether I'm driving or not. What does the "EC" control mean? Is it not using the engine heat to generate that heat, because it doesn't drop my engine temp?

Do I have a problem with my blower motor or is this just no water in the pipes? It perplexes me that the engine-dependent heat would only work with the engine off.

You may have a climate control problem that may, or may not be related to the trapped air in the cooling system. For now at least, (until you get the trapped air issue resolved), run the heat in Defrost mode.

Defrost mode bypasses most of the automatic control system settings. It runs the fan at full speed, and generates FULL heat, regardless of the temperature setting of your climate control. It also activates the AC System.

By the way, EC stands for Economy mode. It prevents the AC from coming on.

Phil

Ignore all the heat related issues for the time being. You can drive yourself crazy.

"EC" stands for "economy". The CCU will attempt to maintain the temperature set on the control wheel but it will not engage the compressor to do so.

Tomorrow morning, check the expansion tank. It will probably be low. Add coolant up to the "cold" mark, not above.

Drive it again.

Repeat.

See if the coolant finally stabilizes in the tank and the temperature on the gauge finally achieves a stable level at cruise.

Then, we'll go from there.

My problem is gone - my upper hose is now firm as is the lower. Temps still the same 82 or so. Early on in this post I mention my symtoms were similar to 83mercedes after I installed water pump, belts, hoses and a thermostat. My hoses were always hard before I performed the work, so I was thinking air in the system also - even though my temps have been OK.

Well guess what I did - went to the parts store and bought a brand new radiator cap :D My system is now pressurized. Seems odd though, as the system was always pressurized prior to the work I did. My tip off was that I always had a tiny trickle of coolant out the drain tube after shut off - with the hose soft. So I thought maybe...... :)

Excellent.

Sometimes the simplest of things.............................................. :cool:

Problem Still Unsolved
 

OK, so after days of driving with the "heat" (I say this since it still comes on only for short intervals, even on defroster, as mentioned in an earlier post) on the water level has not dropped and the temp is still running @ 100C.

So, the next step is to use an IR thermometer, so could someone tell me where I can get my hands on one of these?

I am replacing the radiator shortly, I will update on how that goes, how much coolant I am able to put in, etc, etc.

The lines are squishy because of a bad reservoir cap or a reservoir leak I believe. I am going to get a new one and try it out, and search extensively for a leak.

So far, the following have been ruled out as the problem: air pocket which can be removed other than by an act of God, thermostat, and water pump (unless my new one is not functioning, which isn't possible since it's such a simple design...it either turns or it doesn't).

I plan to replace the fan clutch since there is some play and I figure I'll tackle cooling problems all at once. Radiator also, reservoir cap, and maybe get an expert to figure out my climate control problems if they do not go away if I ever get rid of this temp. problem.

If you disconnect the electrical plug on the top of your monovalve, you should have full heat at all times. If you don't get heat then, you will know that the problem lies with the engine cooling system, not the automatic climate control system.
Sears sells an IR thermometer.