[W126 Coupe] HELP 1985 500 sec a/c overheat prob STILL EXISTS

[Dick Spellman]

Hi Robert,

The temps aren't all that unusual.  You are not overheating!  I'd start 
with replacement of expansion tank cap of correct pressure.  If the 
gurgling continues, remove and inspect the thermostat (engine cold) and 
see if it's installed correctly or blocked with debris.  I know it's new 
but, remove the thermostat and tank in hot water with a thermometer to 
see if it's opening at the correct temp.  If one of these steps solves 
the problem, great.

If not, with hoses, radiator, tstat all basically new, has the water 
pump got any kind of bypass set-up unique to the 85 model year?  I have 
an 83 and recall some strange set-ups on the hoses and pump when I did 
some repairs a few years back.  I don't have the time to review the 
manual and schematics.  Worth asking your mechanic as it's cheaper than 
a bad result with the next step.  If  still no solution...I'd proceed 
with a leak down test.  This will tell you if exhaust gas from one of 
the cylinders is being introduced to the coolant circuit and over 
pressurizing it.  Hence the gurgling bubbling is exhaust gas escaping 
and that's gonna hurt as it's a clear sign of a head gasket failure.  A 
wet/dry compression test will tell you which cylinder(s) are involved 
and a bit more about the overall condition of the motor top and bottom.

Best of luck.

Dick

btb management wrote:

> RE:  1985 500 sec a/c overheat prob

> Have brought the car in four times for the same problem...overheats 

> after short

> drive when a/c runs and immediately hear the gurgling of antifreeze in 

> the overflow

> tank...small amount leaks under the car when turned off.

>

> 1)  The radiator is 6 months new

> 2)  Overheats mainly in stop and go traffic, but after only a couple 

> of miles driving

> 3)  Temp gauge is new and shows 80-100 while car overheats

> 4)  The hotter it is outside i.e. 90-100 causes quicker overheating

> 5)  The a/c is only blows cool when it is below 80  degrees outside, 

> otherwise just blows warm air

> 6)  Center vents were disconnected with a heater core job and too 

> expensive

>      to fix

> Any other tips would be appreciated.

>

> Best,

> Robert

>

>

> ------------------------------------------------------------------------

> It’s a talkathon – but it’s not just talk. Check out the i’m 

> Talkathon. 

> <http://www.imtalkathon.com/?source=EML_WLH_Talkathon_JustTalk>

> ------------------------------------------------------------------------

>

> The MB Coupes Website!

> W126 SEC Mailing List

> Postings remain property of MB Coupes, L.L.C.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.pairlist.net/pipermail/mbcoupes/attachments/20080708/b5a01e28/attachment.html>