The K.I.S.S. principle of overheating cars… - PeachParts Mercedes-Benz Forum

RunningTooHot · #1 09-24-2003, 01:58 AM

Yes, another car that’s “Running Too Hot”, hence my namesake

I’ve started this thread because I was getting a bit of deja-vu. When I purchased my 1984 300D, it was plagued by a hot running condition that seemed incurable. It ended up being that the head gasket was failing & the cylinder head was cracked.

That incident traumatized me sufficiently that I started to assume the absolute worst on the latest orphan car that I just brought home, the 1995 E300D with 324,000 miles. I’m going through mental gymnastics thinking; jeez the head gasket must be going, or - Oh No, is the head cracked? Or trying to think positive – maybe it’s only the viscous clutch.

Well, rather than start looking at worst case scenarios, I started with the most basic: is there enough air going through the radiator. I tore the car apart tonight & found that the condenser on this car (which uses R134a from the factory) has fins that are extremely tightly spaced together, like a very fine comb. Well, guess what? There was enough micro-roadkill (desiccated insects) and other assorted crud embedded in there to fill a small coffee can! I blew it out towards the front with compressed air, used a soft nylon bristled brush to dislodge the species of insects that apparently have glue in their veins instead of blood, and then used engine degreaser. I also used a water-based degreaser after that to remove any possible sticky film that the engine cleaner may have left.

Now there is significantly more airflow through the system, so that should do the trick, right? Well, kind of. The temperature is now much more *stable*, but still Running Too Hot - at a consistent 95-100 degrees on the temperature gauge.

O.K., next step, thermostat. But before I start messing with that, I decide to take out my infrared thermometer & check the temperature of the coolant outlet on top of the engine & the upper radiator hose. Uh, duh, it’s about 8-10 degrees (Celcius) lower than what the gauge is showing

. Unfortunately, I can’t seem to find the temperature sensor for the gauge anywhere, so I can’t test it yet. So the saga temporarily ends here, with chapter two yet to come.

And to think, I was getting mentally prepared to pull the cylinder head. Kind of like fishing with dynamite, a bit of overkill for the situation.

Remember the KISS principle everyone!

Glenn

connerm · #2 09-24-2003, 08:44 AM

You're right. Start with the easy things.
Check hose fittings. Found my 95 e300d 117k had a tiny pressure leak. My tech rotated the hose clamps and fixed leak. Temporary fix identified the problem. Now we know hoses and clamps should be replaced.

leathermang · #3 09-24-2003, 08:46 AM

yes, it does not take much grime, bent fins and insect bodies to really hurt cooling....
If you go to a speciality AC supplier you can get cleaner designed to clean home window units for instance... it is the foaming kind... and there is one kind for the inside fins... and one for the outside... which is more caustic than the inside cleaner... it will really clean aluminum up nicely....

mplafleur · #4 09-24-2003, 08:47 AM

I'm going to have to buy one of those infrared temperature guns and claim that I HAVE to have it for the plane I'm building.

RunningTooHot · #5 09-24-2003, 11:11 AM

Leathermang: Great idea. I’ve seen that stuff at the HVAC supply place, but didn’t think about it.

Mplafleur: It’s well worth the money, as it has come in handy for all sorts of situations. Just remember to read up on getting correct temperatures with it. Different materials have different emissivity factors that can alter the readings. That’s why I checked both the outlet housing (aluminum) and the hose itself. Found mine on Ebay for cheap. Please don’t tell me that you are building a Lanceair 4, I won’t be envious, I’ll be jealous!

Glenn