Ok, well I checked my coolant level a few days ago (I check it once a week or 2 weeks normally), and took off my filler neck cap, and looked inside and it's bone dry. So I top off my coolant, then went to work. 2 days later (today) before I leave work, I decide to check my coolant level just to make sure it's ok, but it's not, and again it's bone dry.

I already checked, and I don't have any visible leaks anywhere. Where is my coolant going?? I know this is not normal, because this has never happened before. I thought maby im actually burning coolant (aka coolant seal failure) but if that were the case, wouldn't I notice white smoke coming out of my exhaust, decrease in performance, or smell coolant out of my tailpipe? I have none of these symptoms.


All the coolant hoses in the entire car have already been replaced, AST replaced with aftermarket, heater hoses, radiator cap etc. The ONLY ONE part of the cooling system that hasn't been replaced is the water pump, and for all I know, it could be the original. I have already inspected the water pump in the past and it's fine. No cracks, nothing. BUT... during the inspection of the water pump, I noticed that I saw a watery fluid (coolant) and it seemed to trace around the water pump where the gasket seals. It wasn't dripping, but appeared to be VERY slowly seaping out. I didn't think anything of it at the time, because I didn't have any leaks or issues with the coolant.

Sorry to make it so long, but I wanted to make sure I provided everyone with plenty of information. What do you guys think? Maby the water pump is leaking so slowly that the coolant evaporates before it hits the ground, or something more serious?

 

trace the coolant flow starting with the most likely to least likely scenario, i just recently found that the coolant line going to my turbo was loose

 

I had a similar problem on a brand new rebuild. turned out the radiator cap wasnt sealing properly. just a very slow leak. try parking over a white poster board and seeing if theres drips on it. tourque down your water pump and look at the radiator itself. remember that the coolant system is under pressure so in order for it to leak the car would have to be running..

 

A funny happened today that I cant explain. Remember how I said that last night I checked my coolant level, and when I looked inside it was dry? Well I left it alone, and this morning I checked it again, and it was right where it should be, but I didn't add anymore coolant?? Idk how thats possible, but i'll keep an eye on the level over the next few weeks, and see if there is really a problem or not.

 

Well, there have been temperature changes lately. Has it seemed to be getting cold? Coolant expands when it's hot and compresses when it's cold. That might be a reason for the disappearance. It's been getting a bit cold where I'm at lately.

 

I had a similar problem. Ended up being a slow leak from the water pump pully shaft... it was a very slow leak. Try topping off the coolant filler neck with distilled water and then watch to see if the coolant level drops. I did this and noticed that there was a slight leak coming from the water pump pulley area immediately.

 

Ok a few months have gone by, and it turns out that coolant IS leaking. First it was the radiator cap so I replaced that with a factory cap, next it was the Filler neck O-Ring and now thats fixed, but its still leaking. NOW it appears to me that its leaking from an allen key type bolt that screws into the top of the thermostat housing.

I circled it in the picture, does anybody know what this bolt is, and what its purpose is??? and what's the best way to fix this... should I reseal it, or should I replace the bolt, and then reseal afterwards?

 

That is a pipe plug. Looks like someone had tapped the thermostat housing for an aftermarket temperature gauge, and then removed it and plugged the hole. Just pull it out, clean it and the threads in the housing, (or replace it) and reseal it with Teflon tape or anerobic pipe sealant. Be careful not to over-tighten it when you replace it - it would be easy to crack the housing. If it were me, I'd get an aluminum pipe plug (McMaster-Carr has them) to use so that the materials and the expansion coefficients would match.

 

had a similar problem with my radiator cap, the rubber seal to it was just a bit out of wack, fixed it in 2 minutes. glad you found this sooner rather than later...

 

Ok well this so called "simple job" turned into a nightmare, but I finally finished up just now... well almost. I removed the pipe plug, and cleaned the threads and washed it in hot water to clean it up as best I could, and wiped down the hole too. The clearance is so tight, that when I was reinstalling it with the fresh Permatex Thread sealant, it sheared off some of the aluminum and there were a few metal shavings floating around in the coolant

SO... then I spend the next few hours removing the air box and hoses to remove the upper radiator hose, and dumped all the coolant that was in the thermostat housing area unto the floor. Then I squeezed the upper radiator hose a few times, just to make sure any left overs of metal shavings in the hose made their way out. Maby I didnt need to do all that, but better to be safe then sorry right?

It says that it drys in 4 hours, but I wanna let it dry overnight before topping off the coolant, just to be absolutely sure that its dry enough to handle the pressurized system. Tomorrow morning before work, im gonna top off the coolant and bleed the air out, then check for leaks. Even if there are no leaks found tomorrow, it will take a few days checking the area everyday, since it is a VERY slow leak. This better work damnit!

 

Sorry for your troubles. I hope it works out for ya. If it still leaks, I would replace the neck. I'm sure there are some used ones floating around the "forsale" section.

 

Agreed. Pipe threads in a questionable location like this sometimes will never seal properly.

Good luck, though, hope it works.

Dave

 

Well it seems like everything is checking out good, the pipe threads are no longer leaking, and now everything's dry. Man coolant sure finds the smallest tightest places to leak from

 

sure does, especially under pressure

 

Glad you got it fixed. Mysterious problems like that are frustrating!

Dave

 

damn Ernesto... you lucked out that it was an easy fix... and luckily you jumped on trying to diagnosing rather then rebuilding

glad you got it fixed

 

Glad to hear its fixed.
For what its worth, as far as I know that pipe thread plug is actually stock. My car also has it, and it seems to be pictured in the service manual too. I've got no idea as to what it was put there for though.

 

FWIW:

Coolant cap and car not keeping coolant / coolant always low

I doubled-checked the new cap, and the overflow valve is not spring-loaded closed.

I went to the McParts store, and all of the new same model number caps (Stant #331) are designed this way.

I did find a Stant 16-lb. cap (pn# 11230) that had the overflow valve spring-loaded closed, and all is well again.

The only way to check is to inspect the cap from the side to see if the valve hangs down, and to gently pull on the valve to see if it is spring-loaded closed.

I'm wondering if this should be a "stickie" . . .

Check out the pics:

https://www.rx7club.com/showpost.php...0&postcount=10

PS: I also found a 13-lb. cap with the spring-loaded overflow valve.

:-) neil