Really troublesome leak from thermostat housing cap
03-24-22, 02:46 PM
#1
Senior Member
Thread Starter
Really troublesome leak from thermostat housing cap
rx7 s5 turbo. I keep having the annoying leak from the thermostat housing cap. I replaced the plastic piece with the billet one and its still leaking. I put a 1.1 bar cap on it which is higher than the .9 bar cap i have on the radiator and its still leaking when the pressure is built up. I've zip tied it down because every time i pull it off the metal tabs on the cap look bent and I thought that would at least stop it from leaking, didn't fix the problem. I'm almost about to RTV the cap in place and see if that works.
does anyone else have this problem because I cant seem to stop the leak.
and I know its not the seal on the thermostat housing because if i run my finger arround the lip of the cap I find its wet, which means its coming from higher up, and the cap is the only thing that's there.
does anyone else have this problem because I cant seem to stop the leak.
and I know its not the seal on the thermostat housing because if i run my finger arround the lip of the cap I find its wet, which means its coming from higher up, and the cap is the only thing that's there.
Last edited by Paulc19; 03-24-22 at 02:49 PM.
03-24-22, 08:03 PM
#2
Rotary Freak
rx7 s5 turbo. I keep having the annoying leak from the thermostat housing cap. I replaced the plastic piece with the billet one and its still leaking. I put a 1.1 bar cap on it which is higher than the .9 bar cap i have on the radiator and its still leaking when the pressure is built up. I've zip tied it down because every time i pull it off the metal tabs on the cap look bent and I thought that would at least stop it from leaking, didn't fix the problem. I'm almost about to RTV the cap in place and see if that works.
does anyone else have this problem because I cant seem to stop the leak.
and I know its not the seal on the thermostat housing because if i run my finger arround the lip of the cap I find its wet, which means its coming from higher up, and the cap is the only thing that's there.
does anyone else have this problem because I cant seem to stop the leak.
and I know its not the seal on the thermostat housing because if i run my finger arround the lip of the cap I find its wet, which means its coming from higher up, and the cap is the only thing that's there.
Really it could only be the aluminum piece or the cap. You've already tried replacing the cap with another pressure cap, maybe try again but with a flat-cap? Assuming your overflow nipple is on the radiator, of course. That's the current setup I'm using, no issues here.
03-24-22, 09:36 PM
#3
Senior Member
Thread Starter
Is the aluminum piece worn down on the little nubs that the cap grips with those tabs? I too have the aluminum piece, no issues sealing here.
Really it could only be the aluminum piece or the cap. You've already tried replacing the cap with another pressure cap, maybe try again but with a flat-cap? Assuming your overflow nipple is on the radiator, of course. That's the current setup I'm using, no issues here.
Really it could only be the aluminum piece or the cap. You've already tried replacing the cap with another pressure cap, maybe try again but with a flat-cap? Assuming your overflow nipple is on the radiator, of course. That's the current setup I'm using, no issues here.
maybe it was because I didn't wipe the old coolant off the seal enough? freaking weird......
03-25-22, 07:36 AM
#4
Rotary Freak
It is weird.
One thing comes to mind; the cap has two seals. There's the lower one that sits on the end of the spring, and there's an upper one inside the cap part. Make sure both are clean and unbroken.
If they're both clean and solid then I'm kind of out of ideas.
One thing comes to mind; the cap has two seals. There's the lower one that sits on the end of the spring, and there's an upper one inside the cap part. Make sure both are clean and unbroken.
If they're both clean and solid then I'm kind of out of ideas.
03-25-22, 09:24 AM
#5
Senior Member
Thread Starter
It is weird.
One thing comes to mind; the cap has two seals. There's the lower one that sits on the end of the spring, and there's an upper one inside the cap part. Make sure both are clean and unbroken.
If they're both clean and solid then I'm kind of out of ideas.
One thing comes to mind; the cap has two seals. There's the lower one that sits on the end of the spring, and there's an upper one inside the cap part. Make sure both are clean and unbroken.
If they're both clean and solid then I'm kind of out of ideas.
Short answer: Clean the cap thoroughly and let it dry because if you leave even a little bit of water on the outer lip its going to leak.
Long answer: Because fluid is "sticky" in a sense (as in water likes to stay attacked to water. If you know how a toilet works you know what I mean) whenever the cap vented the water pressed up against the seal, if there is a bit of water in between the neck and the cap it will push the old water out and replace it with coolant that was just vented, causing the cap to leak and keeping the seal broken.
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