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Old 06-08-2004, 02:25 AM
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Join Date: Jun 2001
Location: Denver, Colorado
Posts: 127
an attempt to solve my overheating problems

well my 300D 78 is overheating like none other. When the car starts running in the morning (60F avg temp outside) for about 5 minutes of driving its already past the 175 mark. 10 minutes of driving here in CO, no hills yet, will bust the temp past the 200F marker. Once i get up this hill thats only 2 miles on a constant incline, the temp reaches 250 redline. A/C is not even on!

I remember 2 years ago i replaced the fan clutch, thermostat, and upgraded the fan blades to the 9 fin version. A radiator flush was done at that time too but i must have done it wrong because i heard some backwashing sounds comming from the top radiator hose, indicating that there was air in the system. this was fixed by a mechanic

I find no oil in the surface of the water level in the radiator so a blown head gasket or leaky one is out of the question. There is also no evidence of any sound commin from the water perhaps thats not bad either. The car smokes when going up hills, you can see some but not that much from the rear view mirror in daylight.

I'm going to do a final run on this again and replace what i may thnk is the culprit of this issues. these are my subjects:

1. water pump and gasket
2. thermostat
3. flush the bastard again the right way
4. pull the radiator out and clean it to death
5. replace temp sending unit---> the temp gauge likes to jump a lot!
6. replace aux temp sending unit ---> fan wont kick in until redline is reached...
7. Radiator cap

what do you guys think? i purchased the parts already...any pointers??

comments are gladly appreciated

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Old 06-08-2004, 12:14 PM
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Join Date: Jun 2001
Location: Denver, Colorado
Posts: 127
well this morning, i decided to take out that thermostat and found some type of generic one in there. I'm am driving without it right now and the temp seems to be ok runing at about 175 +/-10F.....not that bad...

so it turns out that maybe it was a faulty thermos in the first place huh....

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Old 06-08-2004, 12:44 PM
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The Parts are bought and paid for I would do them along withthe flush just for peace of mind that you won't be needing to do the job in February.
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Old 06-08-2004, 07:10 PM
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Join Date: Jun 2001
Location: Denver, Colorado
Posts: 127
alright so i havent put any of the parts in yet...just waiting for it to come in but i have another question

I removed the thermostat today and drove it hard for a good 20miles. The average temperature with a few mountains to climb at an average speed of 75mph was about 210F. Note again that this is with the thermostat....i dont have the A/C turned on either...

so once again is this normal??
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Old 06-08-2004, 07:55 PM
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Location: Milford, CT
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How old is the radiator?
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Old 06-08-2004, 08:41 PM
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Join Date: Jun 2001
Location: Denver, Colorado
Posts: 127
it was my fathers car and i do remember him shelling out a good 450.00 for that Behr back in the early 90's. The radiator still looks pretty new..and i can remember correctly.. i think there was about a good 100,000 miles put into that pile of alluminum fins.

i'll try to post some pictures of it...if i can get back there..
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Old 06-08-2004, 08:50 PM
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Exclamation keep it SIMPLE

FIRST, replace the radiator cap.
spo out
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Old 06-08-2004, 09:22 PM
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Join Date: Jun 2002
Location: Northeast
Posts: 231
I do not know if this is your problem, but I recall that aftermarket water pumps are not as efficient as a MB pump and believe it or not they are CHEAP, VERY cheap, around $30 from the dealership.

Hope this helps

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Old 06-08-2004, 10:33 PM
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Join Date: Jun 2001
Location: Denver, Colorado
Posts: 127
to spo123:

i did order a new rad. cap...i really do hope that this solves the problem!

to junker68:

the water pump that i ordered was a GRAF from only selling for 45.00...i do believe that there is an import version too from that website and was 2.50 cheaper. I heard something about this GRAF waterpump around this forum; something about its design on the propellers that was..... i think..... a positive thing.

not too sure though

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