wankel=awesome

I have a 1984 GSLSE I bought from a forum member last year, and its suddenly starting to run too hot, I think.

This is a totally stock SE with 131k miles.

I know with the change of seasons and it being hot outside should translate to a hot engine, but part of me wants to believe the cooling system should be better.

The engine runs fine, aside from a rich start up and searching for idle when cold.

I run this engine around 40 miles each day for a total of 50 minutes runtime.

At about 25-30 mins of running the coolant gauge floats around the hash mark beyond the middle of the gauge.

If I run the engine hard, or push it, it will go straight to the last line before the hot light comes on unless I let up.

After reaching this temp, the idle quality is terrible, and smells overly rich. It will NOT cool down unless the engine is shut OFF.

It reaches these temps sitting still, or moving down the highway.

Fan clutch is operating normally.

Water pump doesnt appear to have a leak, and radiator hoses arent leaking either.

Both ends of the radiator are getting very hot, instead of just one end that would indicate a clog.





My questions: What should the coolant temp gauge actually read? Is the hash mark that far from normal?

If this sounds like a cooling problem, given the scenario; where should I start first?

j9fd3s

iTrader: (3)

start with a thermostat and coolant change. also while you have the hood open inspect the hoses, and replace any that are bulging/old/etc. also you want to look at the bottom of the water pump for signs of leakage. also check the belts as well.

for the thermostat you should buy OEM, as the stant ones don't cover the water pump bypass port... also the OEM hoses are excellent quality too, not uncommon for them to last 30 years, vs 30 months for the aftermarket stuff

wankel=awesome

Where am I going to get a OEM stat in a few days? I cant run it like this..

mjm4jc

Take the thermostat out and run the car. If the problem was the thermo, you will know. Also make sure that the radiator is filled to the cap with fluid to rule out an air pocket.

j9fd3s

iTrader: (3)

can't do that, there is a bypass port under the thermostat, and removing it opens the bypass so that the coolant can just bypass the radiator, not good

84stock

iTrader: (5)

Drill a bypass hole in the thermostat

DreamInRotary

iTrader: (49)

I had this same issue!

My car would let the coolant pass out of the thermostat at 210degF which is right at that skinny hash mark towards the hot side of the gauge.

After running it at 60mph for a while, it would creep up to that solid hash mark, right before the death zone of slash marks indicating really fricken hot.

Only way it would cool would be to let RPMs go way down, or shut it off.

I replaced my thermostat today with a new thermostat, set to let coolant out at 180degF (same as 82degC, which is OEM) and here are the results





First pic shows that the thermostat lets the coolant out of the water pump and into the radiator at 180degF just like it should, and the second pic shows where the OEM gauge reads when this happens for my car. Pics were taken about 3 seconds apart.

I drove it to test it, stopped and drove it home after it cooled. Same thing happened again, goodbye overheating!

I just replaced my thermostat today, and the thermostat that was in my 84 12a had a bypass hole in it, and I'm pretty sure it was original (as the marking on it was 82degC). But it was still not operating correctly.

wankel=awesome

So were looking at a crappy thermo here?

*Update* Excessive heat in bay seems to have killed my oil pressure sender and O2 gauge. Sigh.

Also, any illustrations on just what bypass hole you guys are talking about? I dont see any such thing on this T-stat, or any of the others from ANY of my stock rotaries... what gives?

84stock

iTrader: (5)

Just buck up and buy a brand new oem mazda thermostat

wankel=awesome

Ive already ordered one from mazdatrix, but I need one sooner than 14 days out.