darren1031

I posted before about cooling issues I was having. My temp gauge was always at the top of normal. The high speed fans
would kick on but not lower the temps according to the gauge. This is at idle.

Yesterday, I removed the thermostat and tested it in a pot of hot water along with the old thermostat I replaced a couple weeks ago.

Both thermostats were stamped 80C.

Thermostat #1: Did not start to open until 90C and was fully open by the time the water reached 94C.

Thermostat #2 (old): Was added when the water was 94C.
it started to open immediately, however, it only opened half as
much as the new thermostat.

How long should it take thermostats to open?
The time it took the water to heat from 80C to 90C was
about 5 mins, but the newer thermostat didnt start to open
until 90C. It's a Wahler, btw.

I think I may have a bum thermostat....even though its new.

Darren
'87 944S

apierce918

as long as its opened all the way i think should be the main concern, when i did mine the old one only opened as much as the new one, but i put them both in at the same time, it seemed like the new one took a little longer to start to open, but it did open all the way, and fixed my overheating problem i was having since more coolant could pass by to flip the fans on

darren1031

My fans do come on. First the low speed and then the high speed.
This is all at idle. But the temp gauge stays at the top
of the normal range. I dont see any coolant coming in at the
top of the tank. It did briefly before the low speed fans kicked
on the for the first time this morning.

I also get no heat. I replaced the heater valve this morning too.
So that tells me no coolant is flowing through the heater core loop.

I have a new fan switch in the radiator, so the fact that the fans come on tells me hot coolant is
reaching the radiator.

I just dont understand why the cooler coolant isnt making it from the radiator to the head!

I dont want to spend hundreds of dollars for a water pump if that is not the problem.

Darren
'87 944S

AR10

Sounds like you need to try bleeding the air out. If the heater is not flowing there is not
enough coolant in the system.

Will Feather

my car also runs hot, and i replaced the thermostat which didnt help. but one thing, i also dont have any heat. im not sure if i have bad switches or wires, but when you flip your hearter on does it at least make noises or anything cus mine dosnt?

darren1031

The system is perfectly bled. I use a Stant pressure tester.
I pressurize my coolant system to about 12psi, check for leaks
and then slowly open the bleeder screw. Air comes out briefly
and then coolant. I do this cold and then I bring the engine up

to temp with the cap off the tank. Once the engine is hot and
the thermostat open, I shut off the engine and repressurize
the system. Never any air, just coolant comes out the bleeder screw.
I really think my water pump is not pumping if that is possible.
The pulley moves when I rotate the engine manually.

The strange thing is, you should see hot coolant returning to the
top of the tank near the cap. Hot coolant is supposed to come through
the small hose that connects to the top of the
drivers side radiator. I never see any coolant returning to the tank.
Even when the high speed fans are on (new fan switch),
a thermometer in the tank only shows 102F coolant.

Darren
'87 944S

sailwa66

It sounds like the system is still not bled properly. When I was having the same issue with mine, I tried using the bleed screw method several times and it still heated up. Not until I parked the thing on a sloped driveway, and jacked up the front end of the car about 12", then bled the system was I able to get all the air out

I'm sure this method is in the factory manual

darren1031

The system is bled. I'm parked on an incline. I get nothing but
coolant at the bleed screw. And this still does not explain
no coolant returning to the tank.

Darren
'87 944S

darren1031

I decided to take drastic action. I removed the thermostat and
put the system back together. Filled with coolant and bled using
my pressure tester with the engine cold and then hot.

Things work perfectly now. My gauge stays at the bottom of
normal 90% of the time. Occasionally it will rise to the middle
of normal then drop back down to the bottom.

*AND* I have heat. About 150F heat, which is what I've measured before when things were working.

So, my water pump must be fine. I'm suspecting my thermostat was opening
barely enough to get a small amount
of hot coolant to the radiator to make the fans (low and high) to come on,
but not enough to cool the head
and bring the temp. down. When I rev the engine, I also see
coolant returning to the top of the tank like it should.

I'll be getting another thermostat and see what happens.

I'm confused about the gaskets though. I read/hear lots of
different things. When I have put in thermostats before,
I put the thermostat in, followed by a rubber O-ring and
then the circlip. The circlip pushes on the O-Ring and holds
the thermostat in place. I have been told there is another
seal inside the water pump closet to the small end of the
thermostat. That I have to look in there with a mirror and
if its not there, the system wont work right.

Can anyone tell me the definitive scoop on the proper seals
for the thermostat?

Darren
'87 944S

austin944

https://rennlist.com/forums/showpost...4&postcount=17
https://rennlist.com/forums/showpost...6&postcount=12

Besides the thermostat seals, there's a seal that you'll sometimes see inside the waterpump outlet that attaches to the pump itself. I've gotten rebuilt waterpumps with and without that seal already installed from the same vendor (Zims). My current pump has the seal installed and it seems to run a little hotter (but still normal) than previous pumps without the seal in there, though it could be something else causing it like the new thermostat.