Weird Engine Temp Issue - PeachParts Mercedes-Benz Forum

latief · #1 05-17-2010, 09:36 PM

Everything is working....

New waterpump (4 months ago), new fan clutch 3 months ago, new radiator 3 months ago...Aux fan relay resistor new, new coolant temp sensor (blue one), new hoses, headgasket 4 months ago.....new thermostat....

AC Charge is good, Aux fans come on first speed with AC on ...at 105 they blast at full speed....new belt and belt tensioner so i know nothing is slipping...

coolant is zerex g-05 %50 distilled water ....

Despite all this, i get ocassional tempreture spikes were it seems to hover around 100ish.....I just don't understand what is the normal temp /AC on with these vehicles... today it seemed to spike all the way up to 105 and beyond for no reason and i was driving and not stuck in traffic....

so what is going on? air trapped in the system?

what is the normal behavior for the temperature on these engines?.....also, is humidity a factor? this is driving me crazy honestly, as i drive with an eye on the street and an eye on the temp guage

I just cannot figure out the pattern for these temp spikes....

Thanks

davidmash · #2 05-17-2010, 10:31 PM

I cannot tell from your post if the temp comes down or if it stays at 100-105. I had an issue where it stayed at about 100 or so constant. I took out my T-stat and put in boiling water and it did not pop. I replaced it and all is good. Temps stay at the 90-95 range with or without AC while driving.

latief · #3 05-17-2010, 10:34 PM

Thanks,

once it spikes, it appears to remain the 100 range....could the new thermostat be stuck/ malfunctioning?

davidmash · #4 05-18-2010, 12:08 AM

I don't think it's stuck because if it was I would think the temp would keep going up. I suspect that it just malfunctioned and the open temp increased some how.

I replaced mine and that was the end of the story. The temps are now where they are supposed to be.

Stick it in boiling water and see if it opens.

thauber · #5 05-18-2010, 10:50 AM

My 93 300e stays just above the 80 mark almost all the time. I have to be sitting for quite some time (5 mins or more without moving) after driving and it being up to operating temp before it goes anywhere near the 100 mark, and never hits it or over. My A/C hasn't worked in the last 2 years, so no auxillary fans on. Only time I had ever heard the aux fans come on was late last year when it blew the headgasket and overheated, and at that time it hit the red line before they ever came on. Just something else other than the t-stat, did you get the system flushed after the head rebuild? Seems minimal, but there could be a bit of trash inside the ports or in the radiator from when it sat for a bit.

latief · #6 05-18-2010, 11:27 AM

This is a problem that seems to be magnified by the use of the AC. although, all systems seem to work correctly, the car cannot keep the temp in the optimal zone once the AC is on (with the fans blowing) ......without AC, temp is within 85-95 most of the time......

Is it ok to run the car for a while with the pressure cap half open so as to burb the system? I will take out the thermostat unit today and inspect....it is a 4 month old Behr unit, so I think it should be solid....

macdrone · #7 05-18-2010, 04:08 PM

Mine hovers at that, remember the engine temp fans without A/C on dont even turn on at 105 degrees.

If your car dont hit red it wont ever go dead.

latief · #8 05-18-2010, 05:47 PM

Quote:

Originally Posted by macdrone

Mine hovers at that, remember the engine temp fans without A/C on dont even turn on at 105 degrees.

If your car dont hit red it wont ever go dead.

I think you are right. The AC with even with aux. fans on seems to add around 10 degrees to operating temp.

I am just going to ignore it for now, although i can't help but feel uncomfortable about this....

Thanks