I have had my RX-7 for about 3 months now. Ever since the first week I got it, the coolant buzzer would go off. I'd fill the rad thinking it was air bubbles, but the buzzer would still go off and my overflow jug just got more and more coolant in it.

Rotary performance replaced my OMP and said they thought it was the radiator cap leaking a tad, but also said my coolant seals where good to go. Cool.

Well, after the rad cap, it still wasn't better.

About 2 weeks later while working under the hood, I noticed a hissing noise. I had just gone on a long drive so the rad was under full pressure. It took me about 20 minutes to find the source of the hissing. It was a TINY pinhole...if not smaller leak in the top plastic cap of my radiator. It wasn't even leaking coolant or wet, but if I put my finger over it, it would stop. I couldn't even see the crack it was so small.

Basically, the engine got warm, cooled, but instead of pulling coolant from the overflow as it cooled and created a vacuum, it would suck air from the crack. This led to my overflow slowly filling up after every hot/cold cycle and leaving air in my radiator.

I got an aluminum OEM replacement from a company here in Dallas for $200. Not bad considering everywhere else wants $300 for a brass/copper rad. It'll be here tommorow

I have been running on borrowed time with bar's stop leak for about a month and a half now. All will be fixed this weekend and I'll be sure to post pics. Now I am sure most of the old timers here know how to do a rad replacement, and I have done it on many other cars myself, but it may help some of the new folks.

Moral of the story? Just because your overflow fills up and your coolant buzzer goes off doesn't mean your coolant seals are bad.

 

had that problem before too, twice!

one turned out to be the copper washer on the turbo not sealing

second time was the water pump, it didnt leak running, front of the motor was dry etc etc, i had to park it in the garage for a couple days

 

This gives me hope. Not sure how I missed this thread when I was searching for the exact same problem. '87 FC NA 5sp, no white smoke, fluid getting into overflow tank but not returning. I know my cap is flakey, so I'm going to replace it anyways. I think my thermostat is gone, so the houseing needs to come off and that's two gaskets to replace. And my water pump may also have issues, while a bigger project, it sure does take care of a lot of possible leak locations. I'm gessing for $400 I can have most of the front of the engine off and replaced. Better then a $2000+ engine out rebuild....

jjwalker, How did the rad replacement go?

 

BE SURE to completely flush your coolant system and get the stop leak out of your system after you install the new radiator.

 

Wouldn't it be just as well to flush the system before* the new rad went on. Why have any of the "hope-in-a-bottle" passing through the new rad?

 

there's probably a lot of it stuck in his old radiator, but sure... either way, get that crap out of there lol.

 

The replacement went well. I was hard on money at the time and got a copper core CSF radiator. it's a bit funky as far as fitment, but wasn't too bad.

I flushed all of the old coolant out REALLY well. I had to replace my water pump about 4 months later and the front cover and water pump housing where squeeky clean. No gum, no varnish, not even mineral deposits suprisingly.