I have had a problem of having to replace coolant nearly every morning after having driven my 1993 RX7 the day before. It usually is about 1/2 a cup or so. Occaisionally, I have had to do this after having driven to work earlier in the day after the car has cooled down. I drive 25 miles to work, mostly at highway speeds. I have never found a puddle of coolant under my car. Recently the coolant system was checked for a leak by putting the system under pressure for 2 hours at the local mazda shop and no leak was detected. The car has a rebuilt engine but drives well. There is no coolant smell. There was a thread from 2001 that discussed this problem, but I think in that case the owner noted a coolant puddle. Thanks for any advice.

 

Check under the TB to see if that little hose is leaking, or maybe the other TB coolant hose that runs behind the UIM. Leaks there may run out and not be noticeable. You are adding the coolant to the water housing neck, right?

But seriously, your coolant seals don't sound good right about now.

 

ahhh, summer. and a young man's thoughts turn to ... Cooling Systems :-/

did you flush your cooling system lately? it can take a while to get all the air back out of the system.

I had very similar problems and it turned out to be a leaky coolant pressure relief cap. when the system cooled, the cap would allow outside air to be sucked back into the system (rather than coolant from the overflow tank).

I would check this first. go ahead and replace the cap, it's cheap insurance.

good luck,

-bill

 

someone else is having a similar problem. Check the recent postings. https://www.rx7club.com/showthread.p...hreadid=323289

Chances are the water passage orings near the exhaust port(s) are deteriorating and the coolant is slowly leaking into the exhaust. Eventually it will become hard to start (restart) when fully warmed up and coolant will blow or bubble back into the overflow bottle. Check for a slightly black rubbery residue (oring material) on the overflow dipstick.

Just my guess from previous experience.

 

i have pretty much the EXACT same issue. im going to have the TB hoses and pressure cap checked now.

 

no black "goo" though. thank God

 

Sorry about the delay in this response. It was indeed the pressure relief cap. The one I had was 13 pounds. I replaced it with one rated at 16 pounds and the coolant level has been full ever since. Thanks a million for a suggestion that solved the problem with so little expense and effort.