Random overheating....need help!

[fordman54935]

I've been having a strange overheating problem lately - Friday night i drove my 88 GT all over town for an hour and the temp never got above 180, then Saturday night it overheated in about 10 minutes. The car warmed up to temp normally and after about 10 minutes it just went straight up to 210, yakking coolant all over the ground. I let it cool down and drove it home, and the temp was fine. The water pump, t-stat, and hoses are all new, and my radiator is a big FMS unit. I know replacing the cap wont hurt (will do when I get home) but do you think it might be the fan clutch? It's speed climbs with engine rpm and seems to move tons of air. What do you guys think?

 

[HyPer-50]

Might want to check the head gasket... I know I had random overheating and had changed out the radiator, waterpump, got an electric fan... couldn't figure it out, and it wouldn't smoke until they pressurized the coolant system and cranked it up.. and sure enough tons of white smoke. Just an idea.

 

[fordman54935]

I would sure like to think its not a head gasket because I just put Thumper heads on a few months ago. There is no smoke and the oil looks great.

 

[GroverDill]

air in the coolant system?

 

[ac09lude]

Fan clutch - mine was doing the same thing and i just did the fan clutch and all is good now!!! give it a try

 

[DTT92LX]

Also, maybe that new t-stat is just a lemon. Happened to me once...

 

[fordman54935]

Also, maybe that new t-stat is just a lemon. Happened to me once...

Its funny you mention that, I actually had to put another one in here already because the first one didnt open.

 

[HISSIN50]

Mr Gasket are very nice stats - that would be my choice.

If the car only ran hotter while stationary, the fan/fan clutch are possible. If this happened while at speed, I would look elsewhere.

Good luck.

 

[sgarlic]

So wait a second.. it boiled over at 210?

 

[ill advised]

My first thought is also "air in the system". Let it idle for a while (cap off, heater on). It may start to spit up coolant every few minutes. If so, let it finish then re-fill.

 

[fordman54935]

So wait a second.. it boiled over at 210?

Well I saw the guage (autometer electric) read 210 and shut it off. The coolant is a perfect 50/50 mix of brand new stuff. By the time I coasted into a parking lot and popped the hood, it yakked coolant on the ground. So obviously the temperature flashed higher after the engine shut off.

 

[AmMscl]

My first thought is also "air in the system". Let it idle for a while (cap off, heater on). It may start to spit up coolant every few minutes. If so, let it finish then re-fill.

My thoughts too:
Also look for bubbles or foaming while cap is off......signs of gasket failure.
Not always will you see oil and water mix during a gasket failure...

 

[AmMscl]

I would sure like to think its not a head gasket because I just put Thumper heads on a few months ago. There is no smoke and the oil looks great.

When you did the head swap....did you flip over one gasket to match the water jackets up.......this is a common mistake and causes a intermittent problem. when looking at a Fel Pro head gasket on a small block FORD (5.0) one will be upside down for proper installation!

 

[fordman54935]

When you did the head swap....did you flip over one gasket to match the water jackets up.......this is a common mistake and causes a intermittent problem. when looking at a Fel Pro head gasket on a small block FORD (5.0) one will be upside down for proper installation!

Yup, I know for a fact the head gaskets were put on right. I'm not getting any milkshake oil or foamy coolant at all.

 

[AmMscl]

Yup, I know for a fact the head gaskets were put on right. I'm not getting any milkshake oil or foamy coolant at all.

I would look at the fan clutch good luck!