Overheating?

i gotta 86 305 TPI z28......

what ive changed:

new 3 core radiator
new water pump
new thermostat (180 or a 195 i forgot)
new sensors (forgot what their called)

everytime i drive a long distance, turn off the car all you hear is the overflow rumblin, smoke comin out of it wit a lil bit a anti-freeze drippin out.....

idk what else i can do to make it stop doing this.....all my fluids are good, i even checked the oil to see if the head gasket was goin but the oil is good.....

im at work right now so i cant type in other stuff, but if theres any other info you need then ill post it when i get back home

thanks to all that help out....

Is the gauge showing that it is overheating? Or are you just hearing coolant bubbling into the overflow when you park it. When the car is parked, some coolant will bubble into the overflow since the water pump is no longer running and the fan is shut off. That is fairly normal (assuming it is not bubbling over). If the gauge is staying in the cool zone (out of the red, probably 220 or below), I'd not worry about it. If it is dripping coolant, you will need to find where that is coming from and correct it (replace hoses, tighten clamps, etc).

Hope that helps.

Air might be getting in to the system & causing this as well.

Buy a new radiator cap. Dollars to donuts that's what it is ;)

Timing out of adjustment can cause it to run hot also.

Originally posted by trackbird
Is the gauge showing that it is overheating? Or are you just hearing coolant bubbling into the overflow when you park it. When the car is parked, some coolant will bubble into the overflow since the water pump is no longer running and the fan is shut off. That is fairly normal (assuming it is not bubbling over). If the gauge is staying in the cool zone (out of the red, probably 220 or below), I'd not worry about it. If it is dripping coolant, you will need to find where that is coming from and correct it (replace hoses, tighten clamps, etc).

Hope that helps.

sometimes when i park it ull hear a lili rumble from the overflow, and sometime it soundsl like its just gonna erupt....the temp goes up to 220, fan kicks on temp drops, n then the temp will sometimes go above 220. its not dripping coolant at at. i need to worry bout this cuz this is my only transportation and i dont have the money to get it rebuilt, buy new engine, or a car....also when the temp goes above 220 it feels like the car just gets weak

Originally posted by krazzycowgirl
Air might be getting in to the system & causing this as well.

how do i check for this??

Originally posted by Sitting Bull
Buy a new radiator cap. Dollars to donuts that's what it is ;)

good idea, ima pick one up today then

Originally posted by Botch
Timing out of adjustment can cause it to run hot also.

true, forgot bout that

I don't know but my timing curve is a little more aggressive than stock but I don't have these problems. I still think the problem lies within the cooling system. Are the fans coming on at the right points

Originally posted by 86305Z28
how do i check for this??

I dont know but a good shop will know because you have to use a vaccum to vaccum out the air bubble.



Was watching Boyd Coddington do this on Amercain hotrod last year.

when a car gets hotter, they lose power, a cooler car is better they say. sounds like something is up, whats an hour of labor worth to save your car, take it to get checked, youll be glad you did. mine drips coolant out of the cap cause the cap dosent get tight its cheap plastic gm junk, so when i hit bumps, and we know this cars take bumps well;) itll fling some out, but if its bubbling like that its probably boiling over, maybe the guage is bad thier not to accurate anyway, pick up those coolant tools from your local advance thier nifty, i got a set myself

Originally posted by krazzycowgirl
I dont know but a good shop will know because you have to use a vaccum to vaccum out the air bubble.



Was watching Boyd Coddington do this on Amercain hotrod last year.

This usually only happens when the radiator is lower than the top of the engine (ie.corvette,coustom rods etc.). Corvettes have a bleeder up top for doing this. This is not to say you don't have a air pocket ,but I dout it. Change the cap and if you have air cond. clean out between the rad.and the condenser,this area always catches crap and lodges in there,which cuts the air flow. Last but not least (did not read all posts) make sure you have that air dam under the radiator and it is not folding back at speed. :)

Also check you lower rad hose,it should not be soft.

Originally posted by IROC-T
Last but not least (did not read all posts) make sure you have that air dam under the radiator and it is not folding back at speed. :)

Also check you lower rad hose,it should not be soft.

ummm air dam? your talking about what directs the air into the intake, correct?? and what do you mean by "not folding back at speed?"

can someone please explain how changing the radiator cap can stop an overheating problem??

Originally posted by aklim
I don't know but my timing curve is a little more aggressive than stock but I don't have these problems. I still think the problem lies within the cooling system. Are the fans coming on at the right points

yeah the fan kicks on at about the 220 mark........

Drill 4 small holes 3/16 in the thermostat. That will eliminate any pockets of air that could be trapped. Make sure your car has the lower air dam installed. Install a lower temp fan switch to turn on the fans earlier.Part number sw555 form autozone will turn on the fan just over 200degrees and its only 20 bucks.If its a 195 thermostat get it out of there. Good luck.

The airdam is a 3" tall and about 3.5-4 foot wide piece of plastic directly below the radiator going across the bottom of the car. It blocks air from going under the car and instead forces it up through the radiator. It's a vital necessity for these cars since they don't have much of a grille.


The radiator cap is designed to keep the cooling system pressurized. Coolant under pressure can run hotter without boiling than coolant under no pressure. If the cap isn't holding pressure, then the coolant will boil very easily and since boiling coolant doesn't cool the engine, it can cause overheating.


Also I prefer to use 2 holes 1/8" in diameter in the thermostat flange.

I agree with Grt.J about the holes ,and you could even go 1/16",maybe rottonJ meant 3/32" ,because four holes at 3/16" is almost 3/4" total and that may be a little to much. Some of the better thermostats already have a purge hole in them ,if you have one of these drill another hole the same size directly(180*) across from it ,that should take care of ant traped air. Grt. J explained about the air dam and the cap ,make sure you get the right pressure cap as too much pressure isn't good either. Look for a 15#only ,most are multiy pressure 14-16# which will work ,but you are better off with a straight !5#'er.

The 220 degree stat is your problem. Id go with the SLP 180 switch for your aplication.

Originally posted by transxtreme
The 220 degree stat is your problem. Id go with the SLP 180 switch for your aplication.

nah its a 185 stat

Originally posted by TheGreatJ
The airdam is a 3" tall and about 3.5-4 foot wide piece of plastic directly below the radiator going across the bottom of the car. It blocks air from going under the car and instead forces it up through the radiator. It's a vital necessity for these cars since they don't have much of a grille.

yeah i look at it and its in a real crappy state, so ima replace it today or tomorrow....

if you have tried everything else... it might be that your water ways in the engine are clogged :( Mine were about 85% clogged. We unclogged them during a cam swap, and have never over heated after that.

Just get an adjustable fan controller from jegs. Hook up two wires and set it for whatever temp you want to. No more overheating, easy as that.