97 E420 - w210 - Engine Cooling SOS!!!
 

Have a problem with engine Temperature....
Cold day keeps ~ 100C (212F), hot day goes to ~120C (248F)

I'm trying to figure out if it is the cooling system itself (does not cool the engine enough) or Engine (generating too much heat)...

If it is the cooling I have only 1 thing left that is not replaced - Water Pump. Is it possible that water pump is working but just not pushing coolant fast enough?

P.S. All the fans are working and kicking in properly

Cooling system parts replaced:
-Fan Clutch
-AC Thermostat
-Front Fans
-Radiator
-Radiator Top Hose
-Engine Thermostat (replaced twice)

My 1995 E420 was running hot - not quite as hot as your, but close. it has essentially the same engine. I was able to attach a resistor to my coolant temperature sensor - now my car thinks that the coolant is warmer than it actually is - and activates the electric fans to keep the engine cool.

I first replaced my electric fan power resistor (it allows for low speed fan operation by running some of the current through a power resistor). I'm not sure if the 1997 has the power resistor like the W124 has. Perhaps a W210 E420 owner could chime in and help.

So - check for the power resistor (it might be bad), then check to see if your model allows for adjustment of the coolant temp. sensor's resistance.

Regards,
Troy K.
1995 E420
83k

all the fans are operational, I'm not sure how would resistors make any difference since fans are getting to the full speed (and it does not help).

on 100 (212F) front fans (grille fans) are kicking in and getting variable speed depending on the engine temp (much faster speed when engine goes ~ 110C)

Inside fan is rotating as well (just changed the fan clutch).

Thank you for the idea though...

Did you try flushing the radiator and installing new fresh coolant

Never tried....., but I think after all the work done in the system most of the coolant has been replaced already ;)

- Last year replaced radiator
- This year replaced hoses
- 2 replacements for the thermostat

Maybe the water pump truly is the last resort. I can't imaging that, however, as the failure mode for a water pump tends to be bearings seizing or bearing seal leaks - not impeller failure.

Is there a cooling system bleeding procedure for your car? Perhaps you have air trapped in the system? I seem to remember that thes enegines are auto-compensting, but I could be wrong.

Best of luck. You could always just wait for cooler weather to solve your problem too.

Troy
1995 E420
83k

First make sure the temperture gauge is working correctly, maybe you only think it's getting too hot.
You also have to be very careful in your assesment of the aux fans: with the engine off, turn the left (drivers side) fan hub and make sure that BOTH of the fans are rotating, the drivers side drives the passengers side via a thin grooved belt. When you are seeing both of them rotating, it can be the engine fan sucking air through the radiator that is making the other fan rotate.
A few other things: The apparent speed of the aux fan can be a very subjective thing, at 100% speed it should be absolutely "howling". The fan or fan controller may be a problem.
You should also ensure that there isn't alot of dirt and garbage build-up between the AC condensor and the radiator, it can collect quite badly between there and you can't normally see it.
Does it cool properly at highway speeds?
Gilly

The gauge is OK since guess what happens after 120C ;) yes... you are right you can hear the boiling in the coolant tank and some coolant can be seen outside (pressure is pushing it out through the coolant tank safety opening.

Both of the fans are rotating. I changed the driver side fan last year (fall) and made sure all assembly is functioning properly. I just double checked fans yesterday.

Yes, at full speed (110C) you can hear the front fans rotating from the inside of the car (with radio off)

There is no dirt at all in the front or in the back of the radiator.

At highway speed I can hardly keep it 95C-100C.

I have a check engine on (but I checked on the computer and this is related to Air Flow Meter)

Thank you for helping me.

Possibly a blown headgasket, I'd have someone check the coolant for CO.

Gilly

Could you please give me some details on how can one check for CO in coolant. I mean are there any tools that I can buy and check myself?... I'm OK with my mechanic replacing the gasket, however I would like to make sure that this will fix the problem.

Pretty expensive tool, it's a CO meter or "detector" as they're referred to as. (CO is of course carbon monoxide). If you had one of these you'd warm the engine up with the radiator (pressure) cap and analyze the vapors coming out of the tank. No I sure wouldn't replace anything on this hunch.

Gilly

Did a cooling system flush.
After the flush filled it with 1 gallon of MB Original Antifreeze and 1gallon of distilled water.

Still having the same symptoms.
While on the highway, I can keep engine ~ 100C, however on long traffic lights temperature is getting really high.

During the flush I checked for spots of oil in the coolant, however everything was clean, I also checked for pressure buildup in the upper radiator hose (when engine is still cold) and did not notice any pressure there.

I need to check for CO level in coolant, but I have no idea how to do this.
Can somebody give me an idea how to do this (what tool will I need to get)

Pretty expensive tool, it's a CO meter or "detector" as they're referred to as. (CO is of course carbon monoxide). If you had one of these you'd warm the engine up with the radiator (pressure) cap and analyze the vapors coming out of the tank. No I sure wouldn't replace anything on this hunch.

It's pretty young for this, but could you have a clogged radiator? Poor coolant circulation will surely make it overheat.

Peter

An IR or heat-detecting digital indicator is an indispensable tool for under $100 to check heat differential at the radiator hoses. The appropriate CO detector to purchase is a 2-chamber liquid design that uses special fluid which changes color when exposed to CO; you can purchase this through Snap-on, Matco, or better automotive tool stores for around $80.

Today I once again confirmed that on highway car can keep 100C, [Da-a new that before!!!]
In slow traffic (city with traffic lights) temperature is jumping around (>100C...)
Interesting fact is that if temp is 110C on traffic light and I put in neutral and send engine to 2500RPM -3000 RPM temperature is rapidly dropping to 100C, if I keep engine at 1200RPM temperature is almost always stays on the same level (with idling speed of 600 RPM after exiting the highway temp is growing).

Since on my way home I have to cross 2 huge bridges (around the mile each one), some more details: bridge on the way up adds the temperature (even though engine is running almost the same RPMs), on the way down reduces the temperature. I think I can understand this fact... but still wanted to share.

Another question.....
I was trying to put everything together in front of me... so I can make some kind of analysis.
Can someone help with temperature measurements?
I have "laser" (IR) temperature measurement tool, however it is useless without knowing the values that are OK for the car.

Can somebody look up the proper (HOT) values for
a) Upper Radiator Hose
b) Radiator (under the main fan)
c) Lower radiator hose
d) Engine Thermostat
e) Water Pump

I will try to get all of my measurements with hot engine and post them here.

I know this is a little far fetched but are you sure that the fan have the correct rotation??

You've already given the approximate temps; you are looking for the temp differentials for a diagnosis. Typically, if the output temp is over 30F different from the input temp, then likely you have a flow problem (water pump, defective stat, etc.) or engine problem (heads, etc.). If temp difference is under 10F, you likely have a cooling problem (radiator, fans, etc.). It's purpose is to guide you in the appropriate direction.

Latest Info:
outside temperature 81F-84F (27C-29C), drove car for 30-45 minutes, temperature didn't climb all the way yet, but this is what I have.

Water Pump: 106C
Upper hose: 97C
Lower hose: 65C
Thermostat: 80C

any ideas?

P.S. I looked at the fan clutch that has been replaced 2 weeks ago.
when engine is not running, I can rotate it with my hand (but I do feel some light resistance and can not push the fan so it would rotate by itself). When I stop the engine this fan will stop almost right away, 1-3 rotations max.

First call the National Weather Service, I believe 180F is probably a World Record High Temperture!

Gilly

Sorry, my, fault, outside temp is in F.. ;) 80F - 27C

Is this correct?
 

You wrote:

"Did a cooling system flush.
After the flush filled it with 1 gallon of MB Original Antifreeze and 1gallon of distilled water."

You may have just typed in the wrong numbers here. On my 1995 E420 (same engine, essentially), the coolant capacity is 16.5 liters. So - that would be about 2gallons on antifreeze and 2 gallons of water to fill the coolant system.

Could you simply have too little coolant in the system? Wouldn't that be a nice easy fix.

Regards,
Troy
1995 E420 83k

Sounds like you have air in the lines. I had this on my 190 and was a ***** to get all out! Need to pinch one line and squeeze another then let off the pinched line! Not sure which in your as I do not know all the hoses on that engine! Also get some Water Wetter!

You might have a defective stat (temp differential is too great between upper and lower hoses). According to your readings, the water pump (next to the stat) is running 20C higher than the stat (which is on the lower side of the pump).

Looks like either your stat is defective, or your water pump is bad (although I don't often see one go bad because of flow problems...).

Just want to make sure I did measure the temp on the pump and not on something else... Pump temperature was measured on metal part that is directly connected to the upper radiator hose on the engine side (sorry for my stupidity if this is a wrong place)

The stat has been changed twice (8 weeks ago and another time 4 weeks ago). Change of the stat did not fix the problem.
When stat was replaced I looked at it and inside it was saying 80C as opening temp. According to my measurements yesterday, stat was at 80C and was staying at 80C all the time (I did couple of tests)

Can Gilly or BenzRepair confirm the amount of coolant in the system? is 2 gallons OK? (We did a flush of the entire system and drained all the old coolant while the engine is hot to make sure stat is open during the drain.

Alex - check your owner's manual. I can't imaging that the coolant amount would be different in the 97 versus the 95. It's the same engine, only without caps and rotors and a modified intake (which wouldn't affect the coolant capacity).

Your owner's manual should have this info somewhere. Wow - could this really be your problem?

Troy K.
1995 E420 83k

To make long story short...
I did not get the original owners manual when bought the car 5 years ago, however yesterday I bought repair service manual WIS (5CDs), hopefully will be able to find the answer there.

Did one yesterday, and it held slightly over 2 gallons (system bleeds itself). Was able to lower temps ~5-8C by pressurizing system and sealing leaks (mainly tightening hoses). Make sure your tank cap seals properly (I.E. does not leak your air pressure off), and verify your hoses are not collapsed when cool (indication you have a system leak). If your system does not pressurize, your car will run hotter.