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Old 12-05-2002, 05:38 PM
Registered User
Join Date: Feb 2002
Location: Canton, MI
Posts: 54
Help: Engine Hot , yes another one

My 1994 E320 w/117,000 miles has been running at 95 deg C everyday and about 99 deg C while in stop and go.

I called 1 800 FOR MERCEDES and they stated this is to hot! Should be 80 - 90 deg C and about 94 max.

I did my homework.
1. Flushed coolant, added MB stuff, 50/50
2. Replaced T-Stat, again MB, oriented correctly
3. Fans are working, come on when over 100 deg
4. Temp return to 95 deg when I drive after being stopped.
5. Turning on the heat drops temp for a short time.
5. 2 of the 3 hoses on drivers side of radiator are hot. The one that connects to the radiator about half way from the top(or in the middle) is just warm. The top and bottom hoses that connect to rad are hot.
6. Spun the fan, it only turns 1/4 turn, so it seems ok.
7. THE RADIATOR ITSELF IS VERY COLD though. I felt around inside the shroud. Even after 15 mile ride.
8. Outside temp is 20 deg F.
9. It acted the same even in the summer.

A. Is there a switch that could be checked?
B. Is the radiator plugged?
C. Can I pull a hose or two off to see if rad is plugged?

Please help!!!

Love this site!

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Old 12-05-2002, 05:52 PM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 11,246
Sounds like it may be time for a new radiator. Pretty straightforward diyer job.
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Old 12-05-2002, 05:56 PM
Senior Member
Join Date: Sep 2002
Location: New Jersey, U.S.A.
Posts: 2,398
Hi John, a cold radiator is not good. Replace it and your problem will be solved. Good luck
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Old 12-06-2002, 01:57 AM
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Join Date: Dec 2000
Location: Fairfax County, Virginia
Posts: 856
Weren't the rads in 90s Es a bit more likely than norm to require replacement early?

Seems like there was a metallurgical issue?
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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Old 12-06-2002, 05:59 AM
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Join Date: Apr 2002
Location: Northern Va.
Posts: 129
I agree....I replaced my radiator after having the same problem. But I suggest a quart or so of CAT Radiator conditioner. I had a CAT backhoe that conditioner was used twice a year for 7 years. Another Cat backhoe bought after mine had radiator problems and conditioner WAS NOT USED. The old backhoe never got hot and anti-freeze looked new after 7 years. The new hoe had to be flushed a couple times...the old one looked new inside the water pump when replaced. I use conditioner in both mine.
1983 300SD 343K everyday car
1983 300SD 285K from junk yard-tooks parts from deer car- runs great. Brothers car.
1984 300SD parts car-Hit deer
1979 300D 175K non-turbo "Doctor"
1979 300d parts car
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Old 12-06-2002, 07:42 AM
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Join Date: Dec 2000
Posts: 368
Have you checked your fan clutch? Check if it freewheels. Get the engine to operating temp, in your case 95 and shut off engine. Observe the fan it should stop spinning after 1/4 turn.

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Old 12-06-2002, 08:11 AM
Ken Downing
Posts: n/a
Just went thru that with my 92 300CE I got my wife a short while back.... Replaced the thermostat.. Fan Clutch.. and Radiatior .. It was near new aftermarket but had a small leak..... Surprise was the best price on a radiatior was at Mercedes.. 229 bucks.. for the updated one.. Problem has gone away..

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Old 12-06-2002, 08:45 AM
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Join Date: Sep 2002
Location: Newcastle upon Tyne, UK
Posts: 215
Just before you spend a lot of money

First, are you relying on the in dash temp gauge? Are you sure it reads correctly? Have you used a different thermometer to check your readings, an infra red or thermocouple driven meter for example.

Second, assuming your temperature is too high, it's not a lot too high. It's worth doing a few things before you bin your radiator.

Feel all over when the engine is good and hot. If the rad is cold everywhere, there is no water getting through. If the hoses to the rad are hot (as you state) there must be some flow, but this might be though the tanks, and not the rad core.

It could be worth running a flushing agent through the system. This may be the same thing as a conditioner that CHAPP refers to.

Then you could remove the radiator and plug all connections except the top most and the bottom most on opposite sides of the core. Stand the rad upright so that the bottom connection is uppermost. Put a hosepipe into the the connection that is now at the top, and see if you get a flow of water from the other open connection. Try reversing the process. If the water comes through OK then your rad is probably OK.

In the UK, some radiator repairers have a rig to test for flow
through the radiator. Perhaps the same is available where you are.

If the rad seems OK, then you may have a problem elsewhere. One or more hoses may have collapsed internally. They may look fine but the inner and outer layers can separate. The water pump impellor may have disintegrated.

Then again, replacing the rad may well solve your problem!
Cheers, Neil
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Old 12-06-2002, 10:13 AM
G-Benz's Avatar
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Join Date: Apr 2001
Location: Dallas/Fort-Worth
Posts: 5,711
Good points neileg!

The most common radiator failure with W124 rads is the plastic inlet hose joint at the top of the radiator, which fatigues and eventually fails at around 90-150K miles of service. The resultant coolant leak is VERY noticeable. The replacement units have a metal shim reinforcement at the same joint for longer life.

The clogged radiator issue is an uncommon one for these cars, so I would agree to have tests done before springing for a $300 radiator that may not need replacing.
2009 ML350 (84K) - Family vehicle
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2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car
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Old 12-06-2002, 10:57 AM
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Join Date: Aug 2001
Location: At Sea
Posts: 1,729
if the tubes are clogged from deposits no amount of flushing will clear them. you need a chemical dip and i don't even know if that can be done on these rads that have plastic parts. if you go through the posts, some will say that your temps are normal. i would guess that you have partial clogging in your radiator. my car behaved the same way and i now am running a lower rated thermostat (83C) that keeps it closer to 80C than 90C. my theory is that there is a thermal equilibrium point (the range that 800 for mercedes mentions) that will tend to move up higher with less cooling efficiency from the radiator caused by clogging. once you go over that zone the system will not be able to dump the excess heat without the help of the aux fans. stop and go driving makes it go beyond that zone, for instance. up to a point, this will be ok but eventually you will reach a danger zone where you will continually reach those elevated temps and be in danger of overheating. the approach i took makes the system take longer to go past that equilibrium point and if it ever does, it cools down fast. my other option is to replace the radiator which costs about ten times as much as the thermostat so i think i can live with the way i have it running now...
1993 300e-2.8
- gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"
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Old 12-08-2002, 04:53 PM
Registered User
Join Date: Feb 2002
Location: Canton, MI
Posts: 54
Thanks guys for the advise. Still need help.

1. I Pulled off the hoses and looked inside the rad. NO, I mean no evidence of any corrosion. On other vehicles I have owened, I have seen a white build up at each tube inlet. But nothing on my MB.

Question: Should I see evidence of the blockage? Help please.

2. I felt all over the rad and it seems pretty cool all over.
3. Again the hose that attaches half way up the drivers side is cool also.
4. The rad does look original though, I can see some external rust at the top of the rad.
5. Looked inside the hoses also, no build up on the inside support coil either.
6. Rad Cap looks good, when I squeeze the hoses I do not hear any air leaking from the tank.

I know 99 deg is not that hot, but I want this thing to last.

Action Plan:
A. Wait to hear if corrsion should be easy seen in a blocked rad
B. Re-check cool stops on Rad, may corners are hot?
C. Investigate if Water pump impeller could be issue?

Thanks again,
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Old 12-08-2002, 07:48 PM
Ken Downing
Posts: n/a
Checking the water pump is a good idea.. but now would wonder about the gage.. Sending unit or gage it self..

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Old 12-08-2002, 07:59 PM
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Join Date: Aug 2001
Location: At Sea
Posts: 1,729
i would replace the pressure cap. if the new thermostat is a Wahler i'd replace it with a Behr....
1993 300e-2.8
- gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"
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Old 12-08-2002, 10:33 PM
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Join Date: Jul 2002
Location: Middletown, DE
Posts: 739
I agree with jsmith. had the same problem-car running only about 5-7C hotter than usual. Replaced a pressure cap and everything was back to normal
1985 190D 2.2l Sold-to Brother-in-law
1996 Mustang 3.8l -"thinks it's a sports car"
1988 Grand Wagoneer - Sold (good home)
1995 Grand Cherokee Ltd -"What was I thinking??!!"
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Old 12-09-2002, 10:40 AM
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Join Date: Feb 2002
Location: Canton, MI
Posts: 54
Thanks, I will replace the Cap.

I did the fan check as suggested.

With engine hot & running I turned engine off and watched to see how many turn the fan made until coming to a stop.

It stopped after about 15 turns, wow. When the engine is off and cold, it only free wheels about 1/4 turn.

Could the fan clutch be my problem?

Why is the radiator so cold then?

Am I looking at multiproblems? Still confused! Help!

I hate to start replace the rad, fan clutch or water pump without investigating all options.

Oh ya, the cooling system is NOT leaking.
The t-stat is Mercedes and new.
I will check the gage after I find out about the fan spin and cool rad.

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