simxxi

My 87 924S started overheating. Replaced water pump, thermostat, Pressure tested, replaced head gasket, oil cooler seals, radiator, No smoke from exhaust. No oil in water, no water in oil. Can not detect any more leaks, pressurized cooling system to 16 lbs, replaced radiator cap with 16 pound cap. Coolant never gets warm in reservoir. purged cooling system but I do notice bubbles in turkey baster when system is topped off from bleeder screw on top of cylinder head while engine is running. It will continue to loose water with bleeder screw open. Cleaned all grounds, checked temperature gauge and replaced sending units, radiator fan switch relay and blue sensor on cylinder head, low speed and high speed cooling fans do kick in and continue to run till temperature creeps toward upper portion of scale, 1/2 to 3/4. I have not let it run into the red zone yet. Ready to pull the head again and send the head out. Any more ideas?

John_AZ

I have been using a 71*C thermostat for about 10 years, in fact I just replaced it a day ago with a new Wahler 71*C thermostat---
www.autohausAZ.com

My temp guage will usually stay at 1/4 and move up to 1/3 to under 1/2.

I also use the Wahler 75*C fan switch
http://www.pelicanparts.com/cgi-bin/...9%2C%20Each%20

I have tried the stock 80*C thermostat/fan switch combo and it always seemed to begin at 1/3 and creep up to 3/4 like yours.

I have the updated turbo pump with the 4.5mm gap from snap ring groove to thermostat ledge.
http://www.clarks-garage.com/shop-manual/cool-08.htm

If you have the 7mm gap the thermostat is different. Most pumps use the 4.5mm gap but you have to measure.



Make sure you use the correct 2.5mm thermostat seal if you have the 4.5mm pump.

Phoenix temps 100*F +

Just a suggestion.

GL
John

peanut

sounds like you covered all the bases its a strange one to be sure. Forgive me for asking the obvious but ....

Have you followed the coolant system with your hand or temperature gauge to see where the hot coolant is getting stuck ? you could have an internally collapsed hose somewhere . Did you use the 944 coolant system schematic to follow the flow ?

If you replaced your thermostat did you check that it is 1, up the right way and 2, opening at the correct temperature (by heating it in a cooking pan with a thermometer ? )

John's suggestion of using the 70 deg thermostat is a good one. I believe It was oem on our Euro 944's . My 944S2 gauge sits on 1/4 in any temperature and if it creeps up to nearly half way on the gauge ,say in a traffic queue, the fans cut in and bring it straight back down again.

clutching at straws here ,... have you double checked you put all the hoses and valves back right when you stripped and rebuilt the coolant system componants and had the heater switched on when bleeding the system?

Cyberpunky

You also need to raise the front of the car when bleeding the coolant system. I use ramps.

simxxi

Done everything suggested. I do have the 4.5 mm pump. I also am running the shim on top of the thermostat with a new snap ring. The only thing I'm not sure of is the 70 degree thermostat. I did replace it with a Wahler. I checked it on the stove and it opens at about 165-175. Car is on ramps, heater on and open, new hoses with the exception of the heater core hoses. I did notice I do have some kind of light smoke and odor coming up out of the transmission tunnel and shifter area. I can not rule this out because I can't tell if it is coolant vapor or oil odor, as for testing purposes I am running only water till everything is back to normal, it also could be oil drip from the back of the block dripping on the exhaust. but being that if I shut off the heater I still am overheating. So that should rule out the heater core and hoses. I also have bypassed the heater core and hoses from the back of the cylinder head flange that feeds the heater control valve back to the waterpump inlet port. Also when I do add water to the bleed screw hole with a turkey baster I do see small bubbles rising in the turkey baster when the water is full. Lower radiator hose is warm upper radiator hose is noticeably hotter. No leaks, verified by pressure testing after replacing the oil cooler seals. Using a temperature gun the readings vary from the front of the head to being higher near the back of the block say 135 from the front to 155 near the back of the block. Readings also vary on the exhaust port header areas from 325 to 475 near the back of the head. Before my overheating issues I was running at about 1/3 temperature, stop and go traffic up to 1/2 temperature on gauge.

simxxi

Thanks guys! I am going to pull the head again this morning and send it out to be tested even though I used a straight edge to check it when I replaced the head gasket last month. I plan on resealing it with the thicker head gasket when I reseal it. My concern is finding a decent machine shop that is competent and not going to rape me and tell me that it is bad just because I tell them it's from a PORCH.....

John_AZ

The '87 924S uses a 150kpa cap or 21 pounds.

The metal shim thermostat gasket support was designed for use with the 4.5mm thermostat seal on later updated pumps. No harm should happen if used with the 2.5mm thermostat seal.

When you replaced the radiator +++ did you flush the engine? I use only 1/2 bottle of Prestone "super flush"--never the entire bottle. Rinse 2Xs and open the rear engine block plug.

Is the condenser clean? Spray with Simple Green and let soak. Use a hose from the engine side to the front/grill to flush. Otherwise you shove the bugs deeper in the parts.

The AC system. Is the compressor dragging?

You can add a product like "Water Wetter" to drop the temp 5 degrees or so.

Do a leakdown and compression test before you remove the head again to see if any problems show up.

Just a few more ideas.

GL
John

xsboost90

sounds to me like you have a plug somewhere in the system- are you sure your system is bled out correctly- heater core open? and have you replaced the radiator? if so does the tube going to the ps of the radiator have a plug in it? I've seen several with the tube capped inside for the s2.

peanut

well there is either still a blockage or the waterpump is fubar

Why don't you remove the thermostat and run it without. See if the system vents ok and the heated water then circulates around the system as it should.
You can also test the thermostat whilst it is out to make sure it isn't jammed .


Only other thing I can think of is either the waterpump impellor is slipping on the shaft or it is jammed in some way. Did you check for impellor clearance by spinning the pulley before fitting the belt ?

You could insert an electric water pump into the coolant system and see if the additional pump lowers the temperature, suggesting impellor slip, or it pushes the air out of the system.