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Old 08-19-2003, 11:50 AM
dwight hinton dwight hinton is offline
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Join Date: Nov 1999
Location: Matthews, NC, USA
Posts: 133
500E Running Hot

After 2 weeks and numerous improvements, I am still having some residual heat issues.

They started with a leaking heater hose. Easy to spot and fix. Still runs hot, boils fluid in overflow tank. Radiator had partial blockage in center section and fan clutch not properly working. Easy enough, replaced radiator & fan/clutch. Radiator cap old and deteriorated. Easy to fix, replaced Cap. Thermostat stuck next. Easy enough, replaced thermostat. Conditions obviously getting better, step by step, but still not 100%. Maybe sending unit/gage is wrong? Easy, checked with temp gun...dash gage is very accurate.

At idle car is fine, warm, but fine 95 to 100 C.
The minute you start to drive off, temp begins to rise gradually up to at times as much as 110C and once when ambient temp was some 90F+, actaully approached 115C. I immediately turned the heater on and temp dropped to below 100C. Activating A/C obviously aggravates the heat condition, activating heater seems to solve the problem. Driving obviously generates more heat, stopping in traffic makes it worse, unless I turn the heater on, bring the temp down, and then it seems O'K until I drive away again.

Yes at times the heat will rise enough to trip out the a/c compressor. As soon as the temps drop a little (i.e. less than 1-2 minutes), the a/c compressor kicks back in. At these times it may cycle many

I do have a belt tensioner which appears less than new. There are occasional chirps which lead me to believe that there may be some slippage but rarely (unless full throttle accel) is the chirp/slippage enough to cause the a/c compressor to trip out. I plan to change it anyway, but could this be the root of evil?

I will check the coolant for Hydrocarbons tonight (i.e. testing to rule out leaking/marginal headgasket?)

I also notice that 2 of the 3 flaps on the radiator shroud are missing. My understanding is that at idle or low speed, the fan draws a slight vacuum and keeps the flaps closed enhancing induced draft air flow across the radiator. At speed, the forced draft air flow (motion induced) overides the fan and pushes the flaps open increasing air flow to more of the radiator's surface. While this may or may not be significant, I will duct take them closed this afternoon and note whether there is any change.

Can you think of anything else that I should check?

While it may not be the solution to the root cause, I am considering a coolant enhancer. Have you ever heard of "Evans Cooling" its at THey have a product that is supposed to reduce/eliminate vapor formation in the system and thereby reduce hot spots, pump cavatation, etc. all of which contribute to engine heat. They admit that under normal operation (i.e. below say 210F) there may be little to no improvement. This appears to be somewhat like the "water wetter?" that I remember everyone referring to in the site.

Any input would be appreciated.
Last thought, I have one or two heater hoses still original on my 92 model. Is it possible that they are weaping slowly (too slowly to notice a coolant loss, but enough to introduce air into the system) and thereby creating an environment conducive to vapor formation, which inturn can increase the potential for some small level of pump cavatation and partial overheating??

I feel that I have allowed my thought process to get far to theorectical, but I have passed all the simple stuff that I can think of?

I will update tonight or tomarrow after the above two tests (1) & (2) are complete.



Last edited by dwight hinton; 08-19-2003 at 11:57 AM.
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