cool spots on radiator (cooling question) - PeachParts Mercedes-Benz Forum

jsmith · #1 12-06-2002, 08:19 PM

i recently picked up a laser sighted infrared non-contact thermometer on ebay. today i was able to put my theory that my radiator is partially clogged to the test. i went on a half hour drive and when i got home i turned the engine off and checked the temps on my radiator using my new toy. i found that the driver side was hotter than the passenger side by about 20 degrees F. temps were fairly consistent on upper and lower portions of the radiator, the difference was which side of the fan i was taking readings from.

is this the sort of discrepancy i'm looking for or is that the normal difference between the hot coolant leaving the engine and cooler fluid going back in?

jsmith · #2 12-07-2002, 06:07 PM

i guess it's the wrong season to post this, i'll try again when it's warmer. last call...

#3 12-07-2002, 09:02 PM

What some mechanics do is, to spray the whole radiator with water. If there are cool spots. The water will still be present on those spots. The coolant circulating will evaporate or burn off the water. 20 degrees F difference on one side might be due to the upper radiator hose coming in from the driver's side on top. You might be reading that instead, of spots on the radiator. You do not need to necessarily have to drive for half an hour either. Do it when idle when, the car gets to operationg temp. What is the problem to analyze the radiator?

jsmith · #4 12-08-2002, 12:48 AM

the engine had been operating around 90C, hitting 100C in stop and go, but aided by a "cool harness" (resistor mod) it drops down to 90-95C. in severe traffic temps are in 95-100C range. without the help of the cool harness the fluctuations would be more severe. i have 40% MB coolant mix and have replaced the thermostat. although some say that this is within normal range i suspect partial clogging as i have seen other cars operate at much cooler temps.

the readings i mention were taken using a laser sighted non contact infrared thermometer. it literally takes the surface temperature where the red dot is aimed. i took readings down and across the radiator as some have suggested and was not really that surprised at what i found. just wanted to get some verification.

TomLatos · #5 12-08-2002, 11:19 AM

As I have posted in the past, I'm still chasing high coolant temps after that head gasket repair. But as part of my on-going diagnosis, I have felt my radiator temp across it's surface by hand, and in-fact did so just the other day when the outside temp was about 20F, just after I pulled into the garage after a 35 mi run at 50mph average.

I noticed that the radiator is very cool in all spots other than the upper RH end. I believe that as the ambient temp goes down, there is not enough flow through the T-stat to heat the radiator uniformly. I did pull the radiator and filled it with hot H2O on the bench with the rad in the horizontal position. and that test yielded uniform temps across the entire rad. Based on that test, I suspect that the rad temps would not be uniform during cool weather.

I am just passing along my experience, but I am coming to the conclusion that my problem is either low-flow from the water pump (I don't know how the pump is constructed and if it can possibly fail in that manner) or that I have a debris blockage in the block or head. I also have low flow through the washer fluid tank coil as it just doesn't heat up the washeer fluid like it did before the head gasket repair.

Good luck, and thanks for your past posts on my cooling adventure.

jsmith · #6 12-08-2002, 01:12 PM

maybe it's just too cold right now to reach any kind of conclusion on this. i think that the temps are supposed to decrease towards one side assuming the radiator is a crossflow type so maybe my readings are ok.

i found this PDF that shows the application:

noncontact diags

i'll do it again in the summer...