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  #1  
Old 10-04-2002, 07:11 PM
Donna W
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Question 92 300TE Running Slightly Hot

Hi Folks,
I've read all of the posts I can find on overheating and radiators on 300TEs and E series. Hope you can help, as I think we've covered all of the bases.

I bought this car one year ago with 144k miles on it. Second owner had had it for 8 years and the valve job was done at 112k. Received maint book with the car.

At 146.8k/Dec. 01, noticed coolant loss. Mech diagnosed weak fan clutch, overpressurized system, and leaking water pump. Repld fan clutch, water pump, and serpentine belt and gates.

At 149.6/March 02, noticed another coolant leak. Mech diagnosed colant leak at heater core, advised dealer repair, due to complexity involved with pulling dash. He BYPASSED the heater core and put a new heater hose on.

At 151.3/May 02 replaced expansion valve on AC


MOVED FROM TX TO FL

at 155.3/ July 02 replaced battery, alternator, and belt tensioner assembly and damper.

At 155.6/Aug 02 rebuilt transmission and complete tune up.

At 156.3/Sept. 02, was driving car when engine overheated. Pulled off road, let engine cool, added coolant and attempted to drive home. Note that it took apprx 2 hours for engine to cool down. This wasn't fun with groceries in car along with 5 year old and 2-1/2 month old!!! Drove 1/2 mile and temp started up into red zone, so parked the car and waited for hubby.

Had it towed to my mech's shop and did the following:

replaced the radiator with a new Behr unit
replaced high speed aux fan switch
replaced coolant level sensor
replaced fan clutch (again!)
replaced upper and lower radiator hoses

They worked on the car for several days, as the new radiator didn't completely solve the problem. The did a head gasket leakage test (fluid color change in test kit indicates leak) and it was inconclusive, so we didn't change the head gasket. Would it be bad 44k miles after valve job? How much does it run to replace? I picked it up a couple of days ago, but waited until today to really drive it.

Started it up, went through drive through at bank (5 minutes) and then hopped on the interstate. All normal, temp was just below 100, like it was before the overheating incident.

After driving approx 17 miles, 20-25 minutes, temp started creeping up to approx 110. I made sure to cycle compressor on and off and that, of course, would make the temp drop to between 100 and 105. I was running at 65 to 70mph, when i slowed down some, the temp seemed to drop. Went to the store and shopped for apprx 1 hour. Came out, started car and temp was normal. Drove home and same thing happened, although sooner, since car was already warm.

Aux fans engage properly, temp never went above 110. Temp seems to go up when car is moving, rather than when idling at stop light---it almost seems like the airflow coming through the grille and radiator is blocked in some way, as there doesn't appear to be any cooling coming from the air moving across the engine while driving. However, I find that hard to believe since mech worked off and on for over a week.

Here's the million dollar question......does the fact that the heater core is bypassed have anything to do with this problem? As I'm in South Florida, my mech advised to not repl the heater core until the evaporator goes, as we really don't use the heater but a couple of times a year.

I love the car, but after having put over $5k into it in a year, I need to make a decision about keeping/selling. I"m willing to try the heater core replacement, if one of you experts thinks that could be the problem.

Thanks for helping in advance!!

Donna

Last edited by Donna W; 10-04-2002 at 07:20 PM.
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  #2  
Old 10-06-2002, 02:20 PM
chazmo
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For what it's worth, replace the thermastat. Solved all my problems with a new T-stat. Sometimes they get stuck and don't open fully which can reduce the waterflow. When testing by just seeing if the hose above it gets hot (T-stat opening) you really don't know if it is opening fully. They're cheap at $25. Replace it anyway and see if that makes a difference. Worked for me.

Charlie
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  #3  
Old 10-06-2002, 04:46 PM
Donna W
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300TE Running Hot

Chazmo,
Thanks, but I forgot to include in my diatribe that the thermostat was replaced. After reading many posts on this subject, I am going to replace the expansion tank cap and check the coolant/H2O proportions. Even though the rad job was just done, I want to see what ratio my mech put in. I also have a hose connection coming out of the expansion tank that had pulled apart several months ago. I was out of town, so I "clamped" the hoses together with elec. tape. Neither of the two mech's who have worked on the car since have replaced my elec tape with a new clamp. There may be a slight bit of leakage there.

Then I'll drive and see how it responds. It's running great, no signs of head gasket failure, so I'll keep my fingers crossed!!

Thanks again!
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  #4  
Old 10-06-2002, 06:37 PM
jsmith's Avatar
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before you embark on further repairs be sure to double check with this forum. what stands out is the fact that your engine temps are around 100 and highway speeds do not bring temps down. that sounds like a busted thermostat to me. on that taped hose - if your mechs really pressure tested it, and it was a pressure bearing hose, they would have found it. if it's the overflow hose that goes into the wheel well, it isn't pressure bearing but there have been reports of elevated temps as a result of that particulat hose. sounds like a good car otherwise - don't give up just yet, but do consult this board!
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1993 300e-2.8
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  #5  
Old 10-06-2002, 08:25 PM
Donna W
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Thank you Joe! I checked and it is the overflow hose. Opened up the little access panel below the pass door and the line was dry, which is good. I've read many posts on this board and there seems to be a strong correlation between head gasket replacement and resultant high temps. Mine was done 44k miles ago, and in the year that I've had the car, temp has always run just below 100.

Therm was replaced last week, I suppose it could be bad, but it does cause aux fans to kick in at the apprx temps specified as others have documented on this board.

I am curious as to why the overflow hose could cause an overheating problem. any insights? I am looking on the board, but having a hard time finding anything so far.

Thanks for your help!!!

Donna
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  #6  
Old 10-06-2002, 08:43 PM
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Join Date: Dec 2001
Location: Southern California, U.S.A.
Posts: 8,508
Whatever happens, you might also want to consider installing JimF's "cool harness":

http://pages.prodigy.net/jforgione/MB_S500.html

Scroll down on the main page and you'll see a description of it. It basically "fools" the auxillary fan into turning on at a lower temperature and keeps it running longer.

Your car will run cooler.

Many of us on the board have installed it, including me and J
smith.

You can install it in one minute or less. Really.

If you can plug a cord into a socket, you can do it.
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2001 E430, Bourdeaux Red, Oyster interior.
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1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
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  #7  
Old 10-06-2002, 08:56 PM
jsmith's Avatar
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Donna,

FYI, your car's engine is not prone to the head gasket woes as the M104 engines of '93+ models. you have the M103 engine which is not particularly prone to the malady. on the off chance that you do have the problem, you will find oil in the form of chocolate colored crud in your coolant reservoir. the test they did for exhaust gases in your coolant is not really relevant to MB engines.

the thermostat, coolant concentration etc. are all still relevant although i don't believe that the fan clutch is ever at fault most of the time. your fan clutches could very well have been ok. it seems that they activate when it is way too late in the game - but that's another story. since you are located in the "tropics" then your cooling system really has to be in optimum condition to keep your engine happy. in the meantime, you may want to investigate the "cooling harness" mod from one of our members. it will give you peace of mind, since your aux fans seem to help with the problem. btw, if you replace the thermosat. make sure you get the Behr thermostat as the concensus seems to be that they are much better than the Wahler ones.

and lastly about the overflow hose - there is at least one post that made a reference to it - never found out much about it...
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joE
1993 300e-2.8
- gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"
http://banners.wunderground.com/bann...L/Key_West.gif
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  #8  
Old 10-06-2002, 10:28 PM
Donna W
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Thanks for your help, very informative. I have ordered the cool harness and noted that a 300TE owner said that it worked great on theirs. I've got my fingers crossed! My car is in beautiful condition and I would have hated to get rid of it---but with two little ones, i can't be driving around with an engine that has bad overheating problems. Now I have hope that we can get it fixed!

Thanks again!! I'll report the results after I get the cool harness.

Donna W
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  #9  
Old 10-07-2002, 03:28 AM
pmizell's Avatar
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Join Date: Jun 2001
Location: Houston, Texas
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What seems odd is that your temps don't go down during highway driving -- which in turn tells me that the cool harness may be of little benefit if any at all.

How does your coolant look? Do you see any signs of carbon inside the expansion tank? The separation of the overflow hose is not an issue ... mine comes apart all the time and I just stick the inner tubing back into the other hose.

Coolant/water ratio could be the problem, so definitely check that, and throw in a bottle of water wetter. My mech told me that with a bottle of WW, it's safe to go down to a 70/30 water to coolant ratio with no corrosion problems down here in scorching hot and humid Houston.

Good luck and let us know what you find
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