I own an 88 convertible. It has 5k on a rebuild I did myself last year and 89k on the chassis. I love this car like it's my baby. I had to rebuild it due to a coolant seal blow out. Recently it developed a coolant leak I cannot figure it out. I am very familiar with the coolant system and of course the car as I have rebuilt it, but I am lost on this one.

The hose to the fire wall WAS leaking about a week ago, I replaced it and it no longer leaks. Well, now there's a new very small leak coming from what appears to be behind the firewall? I looked in the haynes manual and the FSM, what I think it is, is not shown in either. It simply notes "to heater". What? To the heater core right? I am not familiar with what's behind the firewall, but it seems bad.

What do I have to do to figure this out and then fix it? It seems to run down to the transmission and the frame and then leak on the ground, but I cannot find the source of the leak for the life of me as. Please advise.

 

heater core

 

Check both your heater core hoses.Chances are If you had the engine out,.you may have Not Tightened the clamps..
And also check the hoses...Remember the Damn inlet and outlet on the heater core is Brass,so you can't tighten the **** out of the clamps.It will crush the tube.

 

If you were at all vigorous in removing the heater hose it is very possible that you damaged the heater core. If you have coolant leaking inside the car it is almost a certainty that your heater core needs to be replaced. I'd say it's time to bone up on information regarding removal of the dashboard. fyi: it's not that hard.

 

I currently have the EXACT same problem!

I pulled the engine to firewall hose (replaced 2 years ago) and it was fine, no cracks no holes nothin. I went behind the dash and looked at the heater core and the lines, also fine, no coolant residue, no leaks, no moisture. The ONLY thing I noticed was that the inlet pipe (that connects to the engine) was in the shape of a "D" instead of an "O" about an inch behind the tip of the pipe.

I can only assume that the deformity of the pipe somehow allowed cooland to sneak past the hose and run down the pipe? I took some water weld and filled in the deformed area of the pipe, and I'll hoping for the best. I'm somewhat doubtfull however because when I looked at the leak, it seemed like the coolant was flowing from the pipe toward the hose, not the other way around....

 

Rent a cooling system pressure tester from an auto parts store. I had a very very slow leak in my radiator and a very slow leak on my water pump that took forever to figure out. The pressure tester did the trick.

 

Thanks guys. I am pretty sure it's the heater core for me. Thanks again for helping me out. I'll stop back in if I find out that's not it.

+1 on the pressure tester if you can't find the leak. That's how I diagnosed my blown motor last year.

 

Thanks guys. I am pretty sure it's the heater core for me. Thanks again for helping me out. I'll stop back in if I find out that's not it.

+1 on the pressure tester if you can't find the leak. That's how I diagnosed my blown motor last year.

 

Eh just be thankful it's a small leak. Last year I took a friend's FC out to get a new windshield installed. On the way back I decided to blow the cobwebs out of it on the highway, there's nothing like 180+ degree coolant pouring on your right foot to get you out of the throttle...

 

^^Mine started giving me this problem after I was running the car hard when my friend was down for the weekend lol. Seems like the cooling system in the rx-7 is the thing I hate the most. If I had extra money right now I'd buy a new rad and all hoses and everything.

 

I've been chasing coolant problems since I got the car, waterpump -->radiator--> thermostat--> heater hose--> those damned LIM o-rings; the heater core doesn't show the slightest signs of leakage (or wear for that matter) and I didn't loose a drop of coolant until this newest hose leak. At this point the oldest part in my coolant system are the seals

 

Turns out when I replaced that heater hose last week I turned the clamp too hard and it was oval shaped just a little bit. Thus coolant was shooting past it and into the firewall area. Seriously, thank you so much for this reply, because I might have not looked at that again.

I also wanted to note that I checked out the heater core on my car and I can vouch for the access panel under the driver's side. There is absolutely no need to remove the dash and all the vents like the haynes manual says if you're servicing your heater core. Thankfully, that wasn't the problem this time.

Also, I was wondering what type of coolant hoses and clamps I should use for these if they keep giving me problems. Right now I have heater hose and the clamps you get from autozone that you turn the metal ring down with a flathead. Are there better clamps I should get? I chucked the OEM clamps as they were rusted and old when I rebuilt the engine.