Mysteriously vanishing coolant, but doesn't seem like a bad coolant seal; any ideas?
 

So I have a j-spec swap that I just put it. It runs great, but it seems to be loosing coolant and I can't figure out why.
Let me start this by saying I am very familiar with bad coolant seals - I have had 2 different engines that died of coolant seal failure. This seems different though - it does not overly pressurize the coolant system and there are NO bubbles in the filler neck. I can smell burning coolant occasionally, but only once the car is warmed up, and usually only under boost, but not every time I go into boost. I have searched all around the engine bay and can't find any evidence of an external coolant leak.
First, is it possible to have coolant seal failure in a location that doesn't produce the standard coolant geyser? Second, is there something that can fail inside the the turbo to cause it to leak coolant? I searched but couldn't find any good info on how the coolant is routed inside the turbo.

I'm probably going to end up renting a coolant system pressure tester this weekend, but I would like to explore some other options first since they aren't always conclusive and get a few other opinions.

Check all the hose connections (radiator, heater, thermowax, turbo) to make sure no coolant is leaking there. I had a leak at the heater hose connection above the bell housing that took me forever to find.

Also, when water pumps begin to go bad, they leak coolant out of the weep hole behind the pulley. This is sometimes hard to spot because the coolant will evaporate so quickly.

hook up the pressure tester and leave it on there overnight. you will see where it's coming from in the morning.

I checked everything while it was running and warmed up and saw no coolant, but it could be that its just in a location I couldn't see. I'm probably just going to pull the UIM off when I to the pressure test so I can see the hoses and connections better.

Also, I forgot to say that my temps are rock solid in the 180-190 range even with hard driving.

When refilling coolant into an engine isn't it normal to have to add some in the days thereafter because it's not possible to fill up the system 100% full the initial time.

check pressure and then the leek should come out.. check the back heater hose especially that one likes to come loose

This is way past normal air pockets from a new engine install. I've put several hundred miles on it and have to add close to a pint after every time I drive it.

Check the coolant hose on the back of the water pump housing and the hose that goes on the engine block. These two places have common leaks that are hard to see.

Rad Cap, common miss on any vehicle, and a cheap fix. Make sure you presure test it, as well as temp test it. Mine passed the temp test, but wasn't holding presure.

Also, check the bleeder screw on the upper rad elbow. Mine had a cracked seal. It's a $13 bolt from Mazda. (let me know if you need th part number)

turbo seal failure will cause oil and water to leak into exhaust mine did just after a loud pow sound started dumping oil and water replaced turbo and good to go

I got it fixed Saturday. I rented a pressure tester from Advance Auto - it was awesome! I put it on and pumped it up to 1 bar. Within 30 seconds I heard dripping on the ground. Turns out I just didn't tighten the heater inlet hose tight enough. Thanks for the suggestions.

Congrats! BTW, good call on using the tester from Advanced. I made the mistake of getting the one from AutoZone. They don't carry the adaptor small enough to fit the rad. (but they do have one to test the cap, figure that one out....)
-=mike=-

BTW, Advanced Autoparts tester that I managed to pick up doesn't have the O-ring to test the rad cap. But it doesn't matter for $7 I'm going to replace the cap from auto-zone anyways.

And I found my leak. Lower rad hose wasn't sealing on the engine block with the factory spring clamp. Slid the clamp at the engine end of the hose up, slipped a worm-gear hose clamp into place and re-presure tested. If I can avoid repaceing the hose, bonus. It's just a pain to reach, and I don't have a way to catch all the antifreeze.

Glad to hear you didn't need a rebuild.

You got lucky.

Oops. This thread is old.

Thanks! I started to fear an engine job. Presure tester is an absolute requirement when troubleshooting. Now I just have to manage to get "hope in a bottle" out of the system. I took the car in for a flush in January, there is still some copper colored stuff floating in the coolant.

Yep, old thread, but if it helpds the next person that comes across it, all the power to them.

It takes a few times to get the rust out.

Just don't use the super cleaner flush from advance.

Thanks for the warning! Any perticular reason? I grabed their $20 kit last nite but haven't used it yet. Came w/ the heater hose splice jit, a small jug of flush fluid, and two gal of 50/50 premix.

Any pointers would be appreciated!
-=mike=-

I think I have a bad seal. The engine has about 150k miles, so the apex seals are about ready to be replaced. I don't have the facilities for an engine pull/rebuild, so my rx-7 project days are very numbered.

Yeah, why not?

I thought you said it was the lower radiator hose? What else did you discover? FWIW, I got 180K out of my NA before it finally went, and it was a coolant channel wall that crumbled that caused the failure.

USE DISTILLED WATER!!! That's what the old-school gear head at work said to me while wagging his finger....

The lower hose was leaking slightly, I replaced the clamp, no avail.
I found a write up pointing to the shaft seal on the water pump as a possible issue, so I replaced the water pump. (PAIN IN THE ASS JOB if you use the Haynes book.. it's WRONG!) Still pushing air into the coolant system.

I haven't taken the car to a repair shop to test for hydrocarbons in the coolant, but It doesn't take but a few min after start up that excessive presure is pushing coolant into the bottle. I drove about 20 min the other nite, needle rose just above the cold mark and didn't drift very much at 55 mph / 4th gear. When I stopped to get gas, the collant tank was full and bubling. So it's not over heating, but still pushing fluid.

Distilled water.. well, lately I've been geting the 50/50 pre-mix. If I do add water, it's always distilled. Can't say what the prior owner used.

This might sound odd but I encountered this problem once, I had the hoses on the washer bottle cap around the wrong way. I swapped them around and it fixed it.

I wish the problem was so easy on my rx. :(