Alright im having a weird coolant issue. I have had a coolant seal failure and I know the symptoms, however this has none so im stumped. This engine has never been overheated, always sits pretty at 95c and of course temps rise when shut down but we all know its normal.

Engine probably has 4k on it and whenever I take the coolant cap off the coolant slowly goes down and doesnt seem to stop. I think it does stop but it might be stopping at the AST coolant level. AST doesnt go down.

Been driving car for weeks and it does this. No white smoke, coolant overflow bottle is always where its suppose to be at. No coolant buzzer or loss of coolant during operation, just when I remove cap it goes down. No puddles on ground.

Id say this started possibly when I removed the rear TB coolant line to remove my Water Temp gauge. Hose was cut for the T so I just added a hose coupler to seal up the two pieces.

 

Since an FD is the only car I know that has an AST that must be the car that you are referring to.
So,make it a habit please.You need help?,people can help!,but can't help you without you helping them so they can help you!!!!..(make sense?)

https://www.rx7club.com/new-member-r...swers-1030345/

 

A few things that might help. Any modifications to the coolant system? Aftermarket radiator, deletes, do you have a v mount which may have pushed you radiator further upwards or downwards?

What happens if you DON'T take the cap off and just take the cap off the radiator? When you take the rad cap off does the coolant overflow bottle level also move or stay the same? Have you pressure tested and made sure there were no bubbles in the system?

 

I have the exact same problem, but I have a stock radiator can't seem to figure why this happens.

 

Sorry forgot to mention it's a Fd. Coolant system is all stock with the exception of a metal ast and upgraded radiator.

Overflow always seemed to stay the same. Just above the full mark.

 

has to be going somewhere! check your oil, overflow bottle, and the ground.

 

I check oil everyday and It isn't bubbly or showing signs of coolant in it.

 

If not what jjandrose said then maybe your coolant to water ratio is off. Start simple and hope right?

 

Bro overflow you can test open the radiator cap ! you can see the thottle body have one pipe must open .start the engine add coolant you can see the thottle body pipe have a water came out now you can install back the pipe ! This can exhaust the air !

 

pressure test the system.

 

It's most likely due to one of three reasons...:
1) It's draining on the floor
2) It's flowing right into your overflow tank either due to gravity, broken coolant seals, or AIR
3)Air in the system. This is the most likely cause... Refil your coolant without the radiator cap. Keep cap off. Run vehicle until operating temperature is reached and thermostat opens. Run for fifteen minutes toppiung off coolant in radiator as necessary and keeping an eye on the temperature gauge for overheating. once no more bubbles are coming out of the radiator coolant wait ten more minutes, top off the coolant in the radiator fully, and reinstall the radiator cap. At this point You'll need to check the overflow tank and be sure it's topped off too. Shut off the engine. Air should now be out. Please be sure there is no air in your system and then post back respectably (as in once done)

 

While you're at it ^ pressure test it, if you don't have one, go to a shop.

 

^This
^And this.

If you're confident there's no air in the system (usually indicated by a boiling sound after shut-down), it's not leaking, and not being left in the overflow...then the only explanation I can think of is that it's being consumed.

 

That would suck if its consuming it, engine was just rebuilt due to a overheat. After shutdown there is boiling so I'll burp again with the Leslie funnel and report back.

Can't imagine air in the system would allow it to keep going down for weeks. And it only goes down when cap is removed.

 

you're only seeing it go down when removing the cap due to suction, which can happen if you have a small leak you can't see.

pressure test it, find the leak and fix it.

 

Last time I pressure tested I couldn't get the stupid autozone tester to seal on our cap. What method do you use?

 

find one that works, or you may have a bad AST. you can also mount it to the thermostat housing, it should have an adapter(this also allows you to test the AST and cap).

 

Yeah that's the one that wasn't working. The adapter to mount it to the thermostat housing. Also I got my ast cap from autozone and hope that's holding up well and releasing at right pressure.

Maybe I'll do a ast delete because I did have a problem with the hose on the bottom of it rubbing through.

 

Had a similar problem with a pressure tester- gunk the inside seal of the sucker with blue RTV (right around the side lip) and try not to get it *inside* the cap area- you just want something to help seal around it. It'll wipe right off when you're done.

 

The problem I had was the autozone adapter wouldn't go on and stay on tight on the thermostat housing. It was still able to move. It was the smallest adapter too.

 

If you're willing to put in the money, harbor freight has one for 80 bucks, or go to a different auto store or pay a shop to do it.

With my problem, it would (kinda) stay on, so we gooped the inside to help the seal, and someone basically had to hold their weight against it while the other person searched for leaks.

 

if it won't seal just get an o-ring that fits inside the pressure cap neck, it only serves to help seal the tester to the housing. just remove the o-ring before putting the cap back on, sounds like that pressure tester is about due for retirement.

 

pressure test !

 

Problem solved I believe. Pressure tested the system held pressure fine with no drops. Pressure tested the cap and found its releasing at 8 psi. Stupid kragen, never buying from auto parts store ever again. Got another 13 psi cap. No gargling on shutdown so far so all seems well.

 

Congratulations to settle the problem!