High running temps solved! - PeachParts Mercedes-Benz Forum

#1 07-23-2002, 10:00 AM

First of all, I am new to the list and this is my first post. I felt that I should offer my recent experience with a hot running engine after spending a lot of time researching the tech forum with other members experiences. The car was diagnosed by the dealer as needing a new radiator and one auxiliary fan. Both were replaced and the problem was still there - running 100+ c .
After reading a post (sorry I can't remember exactly who) I decided to replace the thermastat. A local parts guy had a German made 82 degree thermastat made by "Go-Rad". The parts person indicated that this was considered an oem type replacement. I understand Behr is original equipment, but I wanted to take advantage of a lower temp rating. He indicated that even though the thermastat in the car may seem good by checking the hose to the radiator to see if it is hot , sometimes the thermestat doesn't open fully and can be restrictive as they get older. Anyway, popped the newone in and immediately back to 82-85 degrees. To anyone else with a hot running engine, I would suggest starting here first.

Chazmo

J.HIDALGO · #2 07-23-2002, 11:44 AM

Keep It Simple Stupid! Sometimes we go for the more complicated stuff...

Ken300D · #3 07-23-2002, 01:31 PM

The impression I've gotten from reading posts over the past year is that there has been a bad production run of OEM thermostats.

Don't know exactly what to do about it - but probably would look for an aftermarket part here.

Ken300D

stephenson · #4 07-25-2002, 03:44 AM

Way to Go!

I have been thinking about overheating (since mine did) for awhile and it comes down to some simple stuff that gets all mixed up ... the logic trail is pretty clear.

Try this on:

If the engine overheats while running at 50 mph in normal temps with air conditioning off, it probably isn't:
- viscous fan
- electric fan
- maybe not even a pressure leak

It may be:
- tstat
- radiator
- maybe a pressure leak

I have yet to read of someone with a bad waterpump that affected cooling - they may blow a seal or bearing, but I am not sure how they would pump less unless vanes were worn down (hard to imagine) or the housing or inlet/outlet were clogged.

If overheats at idle, it could be:
- viscous fan
- electric fan
- pressure leak
- tstat
- radiator

OK, so what is easiest thing to do?
- replace tstat
- check for pressure leak at cap (most likely)
- see if electric fan is running (pretty easy)
- check to see if viscous or mag fan clutch is locking up (easy)
- last thing - replace radiator (it is the most expensive)

I am finally beginning to think right about this overheating thing ... although, I could be wrong.

David C Klasse · #5 07-25-2002, 04:24 AM

What were your symptoms? Was the engine running really hot in traffic?
Is the temp now @ 85 ALL the time (even in traffic??) ??

Thanks!

renok7 · #6 07-25-2002, 08:10 AM

I can't believe that the dealer went ahead and replaced the rad & fan without first trying a new thermostat. Makes one wonder.

tstarr · #7 07-25-2002, 11:42 AM

Agree to start with thermostat first. I had the water pump blow on me on my last vacation trip, in South Carolina while I was heading back to Maryland. I kept water in the car, but it never even came close to overheating. That was my original worry and I finally got to the point where I just stopped to put water in it, but the temp was fine the whole trip. I used a lot of water, though!

But when I got the car from my Father-in-Law, he indicated that the car had been running a bit warm for some time. I thought, sheesh, I'm just going to put a new thermostat in without doing any testing just because I don't know how long it's been in there. It has run cool ever since.