My car has a new radiator, and a new radiator cap. It ran great for a while, but now it overheats after driving for a while. The fan works fine... and kicks on when it is supposed to.

I'm thinking that the thermostat is stuck partially open or something.

What about my water pump? Would a car run if it was malfunctioning?!

 

if the seal isn't damaged then i'd say you don't have the cap tight. the car will work/run with a bad water pump.

------------------
ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

 

the cap is on as tight as it will go.

what would you suspect? thermostat or water pump? maybe collapsed hoses?!

I'm at a loss here guys and gals.

 

Bad radiator, bad cap, cap not on tight. Check stuff, don't assume that just because it's new it's right, if it doesn't work right then it's got something wrong with it. If it leaks, there's a hole.

Thermostat stuck partially open would tend to make the car take a long time to warm up. That has nothing to do with whether the radiator cap seals or not.

Define "overheating": from the factory, the fan in these cars doesn't even come on until the gauge is almost to the red zone. i.e., fan kicks on when it's supposed to = gauge goes almost to the red. That's noraml. That behavior does not constitute "overheating". If you have coolant spewing, and you're calling that "overheating", then you need a radiator cap.

"The simplest explanation that fits all the facts is usually the right one."

- Occam, ancient Greek philosopher

------------------
"So many Mustangs, so little time..."
ICON Motorsports

 

He's right I had the same concerns about my car soon after getting it the guage always goes to red before fan kicks on even had a shop do a thermal reading on the engine and they confirmed it was operating properly.

However if this is not the reason for your concern of overheating you may just have a bad cap. You can tell if the water pump is not working by taking radiator cap off and running engine if you can see coolant flowing through radiator then the pump is good. Plus you have temp sensors so it could be one of any number of things. You need to be more specific as to why you think it is overheating.

Mark

 

Run it with the cap off for a while. Look inside at the flow through the radiator. Are there a lot of bubbles in it? If so, you might have a leaking head gasket or a cracked block or head. If you are blowing compression into the cooling system in one of these ways you will have a problem like that.

 

ok... here's one.

I just took it out for a ride, and the fan kicks on and stuff... but the temp keeps creeping up and up.

After my car cooled down a bit, i went out and tried to remove the radiator cap... it was almost as if there was a vaccuum inside of the system. A rush of air sucked into the system when i got the cap off.

Bad news?

 

No, good news. That's what it's supposed to do. When the coolant cools down, it shrinks more than the metal does, so it creates a vacuum in there. That's supposed to unseat the little rubber check valve in the rad cap, and draw whatever coolant is in the bottle, back into the rad. That way, after a few heat-cool cycles, all the air will expel itself from the cooling system through the bottle, and the system will be completely topped off with coolant.

So when the fan came on, did the temp start to come back down? It should have, maybe slowly, but it should have cooled down and eventually reached a point where the fan should shut back off.

------------------
"So many Mustangs, so little time..."
ICON Motorsports