190e is still over heating.

My specific questions are
1.) how do you test the auxillary water pump?

2.) how do you test the viscous fan clutch?

3.) Is the fan shroud cosmetic / saftey or does it improve the vaccum effect from the fan clutch? e.g. does it have to be there?

3.) Any other suggestions or Ideas?

Here is the history:

car: 190e 2.6 1993
Problem: car overheats and/ or runs right beneath red temp line only when it idles or I sit in traffic for more than 10-15 minutes or if I'm driving slow (e.g. rpms <2000rpm). This occurs regardless of outside temp.

The temperature rises much faster if the heater is on. No difference with the AC on.

I have found that after running the car such that the temp rises to 80 dergrees C, and let it Idle. The temp begins to creep up rather quickly up past 100 C (it will overheat if I let it go). The auxillary fans kick on but does not cool the temp down. If I then rev the rpms to 3000 the temp quickly decreases to 85-90 within 30 sec to 1 min.

Operating temp when driving is just a touch above the 80 degree Celsius mark. No problems what so ever when the car is moving as long as the RPMs are greater than 2500-3000.

Recent work:
1.) replaced the water pump with an OEM graf water pump, changed hoses

2.) changed radiator fluid (40:60 anti-freeze to H20 mix),

3.)tried both the old Mercedes thermostat and a wahler thermostat. (boiled them both to make sure they open)

There are no leaks in the system by visual inspection.


Please help

Thanks

Aaron

I rev the RPMs to 3000 in park (the does not have to be moving to cool, the RPMs just need to be more than 3000).

Are the fans coming on? If not do a search. There is a fused relay on the firewall in front of the drivers side. Check it if the fans are not coming. Search should provide alot of information concerning operation of the cooling fans in front of the radiator. Doesn't sound like they are running.

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Jim

only driving with RPMS greater that 3000 or Idling in park with the rpms greater than 3000 cool the temp down to 80-85 degrees celcius.

The auxillary fans kick on at just above the 90/100 degree slash mark.

My first guess is the radiator. I have seen many of them plug up in the middle...you can't clean these well because of the design of the tubes.

I'd replace the radiator if you know it is not the head gasket. To check for head gasket failure, there is a block tester that goes on top of the coolant tank. You can get it at NAPA stores. If the head gasket is OK, replace the radiator.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

This is an novice question I'm sure but I'm trying to learn.

How is the head gasket related to the overheating, and why does it resolve with an increase in the RPMs.

Thanks.

Aaron

The revs allow the fan on the front of the engine to turn faster, moving more air through the radiator. Driving down the road does the same thing - you are getting air flow through the radiator which is cooling it off. At idle you are not getting air through the radiator enough to cool it down. It should not be going up that close to the red line. Keep in mind too that the fans on the front of the radiator are two speed. Can you tell when they go to the higher speed?

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Jim

Head gaskets will usually boil over all of the time, but on occasion, they can be only noticeable when cold.

If the head gasket leaks, it will aerate the coolant and heat it with combustion gasses. The result is a hot engine.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

I'm not sure if I'm the Don you're looking for (screen name is ddrake3) but I think I can solve your problem, as it has happened to me. There are a couple of things to check... #1) Check your radiator cap to make sure the seal isn't rotted... if it is, the water in your coolant can evaporate, leading to a low coolant condition. 2) once you know the cap is good, top off the coolant WITH THE BLEED SCREW OPEN until coolant just begins to come out of the bleed hole, to make sure there's no air in the system. Then let the car warm up with the screw open and the heater on max. You'll notice from time to time that air bubbles will come out of the bleed hole. Yes, you can leave the bleed screw out while the engine is running. Once hot air comes out of your heater, carefullly recheck your coolant level (don't forget to open the cap slowly, allowing pressure to escape before taking it off.) I use a heavy towel to make sure I don't get burned by coolant. If hot air doesn't come out of the heater but the engine is warm, rev the engine a couple of times-- that should solve it. Once you've done all this, your problem should be solved. I have a number of posts on the topic on this site. Post again if you need more info. This post can only be 1000 characters long...

Don

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Don Drake

1990 300E 125k Miles
1994 S420 100k Miles