My thermostat housing has started leaking coolant at the seal. Can someone help me diagnose the cause?

The coolant reservoir seems to only refill the coolant when low but none is ever returned to the reservoir since I bought the car in December. I've had to refill it about three times now.

The temp guage doesn't seem to go up over the 1/3 mark. The upper hose is warm. Coolant leaks onto my engine from the seal of the thermostat housing unit, causing white smoke when I turn the engine off. This started 2 days ago. I've only driven it about 5 to 6 miles twice in the last 2 days. The first time I thought it might be because the pressure cap to the thermostat housing was loose.

Last, I live at least 30 miles from a dealer, am new to the area so I don't know anyone that can drive me. If needed, can I buy a thermostat from my auto parts guy? Or should I mail order one?

PS I have an '88 RX-7.

Thanks. I tried to avoid the stupid questions.

Carolyn

 

Check that the plastic thermostst neck is not cracked.
I seal mine with RTV (silicone sealant).

 

Based on reading similar questions about replacing thermostat, there is nearly universal agreement that you should only use the OEM Mazda thermo. Appears several have had failures with generic replacement.

Good luck with a ride. Maybe you can get a round trip taxi at discount?

 

There is rubber "O" under the housing. With time it deteriorates and will seep water, esp.when cold. Have had to replace mine twice.

 

Take the hose off the thermostat housing.

Remove the two 12mm (possibly 13mm) wrench size bolts that hold the housing on.

IF the gasket seems in good shape, leave it alone. Buy some Permatex, High Temp, RTV Silicone and apply it to the base of the housing. Just enought to squeeze out a bit as you install the housing. Wipe off the excess.

Apply some grease to the two bolts you took out earlier. Helps prevent corrosion later. The ones you took out probably look a bit corroded on the threads.

Reinstall the same way you removed the parts. Might wait a hour before driving the car.

If the gasket looked ragged do what you know to do....buy a new one. A buck maybe. I don't know. Never had to buy one.

The leak at the housing is the reason you have to refill the radiator often. You need a completly sealed system for the water in the overflow to return as the car cools down.

 

Sorry, didn't read as far as your vechicle '88-Yup gasket, no "O" ring.

 

As Sure Shot mentioned check for a crack in the plastic neck. I would not RTV it. When mine cracked I replaced it with an aluminum one from a FD. Problem solved.

 

***coolant at the seal*****

 

Thanks guys! I'm going to try the gasket and sealant as soon as the rain stops this weekend. I'll let you know if it works.

Carolyn

 

The thermostat neck is only plastic on the S5 cars... not the 86-88 (Mazda trying to save a buck again on those S5 cars).

 

Wrong, they were saving weight! that is what makes my vert such a great investment (?)!!

that plaxtic neck is $48 OEM!

 

Weight savings??? yeah on the S5, they drop the uberlichect german Jack that saves like 5 lbs and instead put on a plastic thermostat neck that only saves 10 onces...

Uh yeah... weight savings... okay what ever you want to convince yourself.

 

Well , I think my neck is plastic. But I feel a little blonde, because the year is 87 not 88. The leak is at the neck, which holds the cap. Could the cap be bad also?

There is not a gasket at the filler opening on the thermostat housing unit. This is where my coolant is leaking. Do I still use the silicone? The auto parts man sold me water pump & thermostat housing RTV silicone.

Carolyn

 

Learned a bunch. Thanks. Leak is better but not fixed with sealant. Either neck is cracked or cap is shot. Either way I guess it's the same. Have to replace both.
Right? Neck is plastic. How do I find an aluminum one?

Carolyn

P.S. I have a 87 Mazda RX-7 not 88 my error.

 

icemark, your wrong, mine is plastic and its an 88, but mine was leaking so i upgraded it to a fd one.

seems like her leak is in fact at the cap and not the thermostat housing...

you need to get a metal neck, and a new cap and your good to go.