Possible Bad Head Gasket

[jessetooslow]

Hi, I am new here, and also a new supra owner. I just bought a 1990 Supra Turbo with the automatic tranny. thsi is my problem, my car is not leaking any coolant, but I do smell the coolant strongly, it does not blow out white smoke. The temperature will go up, then go down real fast, just 1 time. then the rest of the time it is fine, any suggestions, my friend thinks it s a bad thermostat, any suggestions will help. thanks:aigo:

 

[jdub]

Your friend just might be right. Get a Stant SuperStat...cut the jiggle valve off it before you install. Make sure you get a new gasket for it too.

 

[jessetooslow]

what size thermostat should I get, should I go with a smaller one? why cut off the jiggle valve?

 

[jessetooslow]

supposedly the Head gasket was done already, not because it was blow, but because the car sat for awhile. the brakes were frozen and everything.

 

[jdub]

In your climate, likely the stock 190 deg will be best. It's a 52mm stat. Cutting off the jiggle valve allows a small bit of flow at all times through the stat and helps rid the system of air. Also stops pressure from building behind the stat and holding it shut. You might even want to drill it out just a bit.

 

[jessetooslow]

cool, thanks for the help, I hope thats the cure.

 

[jdub]

The only thing that concerns me is the coolant smell. Was the HG stock and what torque was used? Has a re-torque been done?

 

[jessetooslow]

I believ it was stock, it was a old guy I got it off of. The shop that did the work were hacks most of the intake bolts were not tighten or installled, I had to have those doen over, but didn't check the head gasket, it runs good now.

 

[mattjk]

probably not the thermostat, they are either good, or bad and stuck open.

the quick rise and fall of temp is probably due to a huge air bubble in your system.

The smell can come from coolant being spilled all over by the previous owner.

 

[jdub]

Ok...highly suggest you check the HG bolt torque. The shop likely used the stock 58 ft/lbs of torque. You want 72-75 ft/lbs (assuming stock head bolts)...increase the torque using this sequence (3rd pic down):
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?Section=EM&Page=55

You will need a torque wrench, extension, and 10mm hex.

Mattjk - I had several thermostats do the exact same thing...cut the jiggle off and it has not happened since.

 

[mattjk]

good idea on the retorque. I'd suggest not driving it until you torque it to the higher spec.

 

[jessetooslow]

yeah, I have ha checked for air pockets, I'e had a few, I could swear I heard a hissing sound from the back of the motor the other day, could be a leak in the head gasket, I have a feeling it just needs to be tighened, I might as well, just buy a nice aftermarket one and do the timng belt, my car has 114,000 miles.