When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Have you blead the coolant system while the heater is full blast? Meaning the heater core is getting coolant through it? Most times, the heater control valve fails and you won't be able to blead the system properly.
I Don't Run a turbo T-stat on my cars, I drive them in the summer only. Think about what i happening on startup, Everything is at the same temp, and when hot.. Again with T-stat open Just coolant circulating..So to me there is no point in running it if I never drive it in the cold... . I think the original intent for the turbo t-stat was to allow the coolant that is in the engine to stay there until operating temp is reached for colder climates... I also Don't run the "Sealing ring" around the main thermostat so when the system gets filled there are no pockets of air, it purges better... MY .02
Now I’m not convinced PET diagram is wrong... looking at the Clark’s diagram again. The TC has a pump to circulate with the reservoir operated by a thermo switch. If that circuit gets too hot then the aux t-stat opens by heat conduction down that hose. Then the hot coolant would be circulated through the main radiator.
The 944 Turbo cooling system operates bypassing the radiator until the coolant temperature reaches 83 °C when the thermostat opens. After the thermostat opens, coolant is circulated through the radiator and back to the suction of the water pump.Flow through the heater core is controlled by a vacuum operated diaphragm valve the fail open on loss of vacuum. Vacuum is supplied to the valve operator via a vacuum solenoid in the HVAC system.
With the engine shutdown, if the temperature in the discharge cooling line from the turbocharger rises to 115 °C (as sensed by a temperature sensor), the electric turbocharger cooling pump comes on to circulate coolant from the expansion tank, through the turbocharger, and back to the expansion tank. The turbocharger cooling pump also comes on for 25 seconds any time the engine is shut off regardless of the temperature in the discharge line.
When the engine is running, a turbo thermostat opens at 82 °C. The water pump then draws coolant from the expansion tank through the non-running turbo cooling pump and through the turbocharger bearing housing. A check valve in the expansion tank prevents coolant from being drawn from the turbocharger discharge line back to the expansion tank. Otherwise flow would bypass the turbocharger.
So it looks like the Turbo pump only comes on if the engine is off. Therefore I assume that the only way to get coolant through the Turbo while the engine is running is to have the thermostat spring on the hot side of the engine so that it opens when engine coolant temp reaches 82C.
I have a coolant coming from this location. It was not severe enough to make drips. It would sit on the block (think it’s the block) and evaporate. I only noticed by chance. I was losing a small amount of coolant but enough to cause my temperature needle to rise in the 3/4 zone instead of hovering around 1/4 - 1/2.
OK This is VERY and I mean VERY important... PAY CLOSE ATTENTION TO THE LENGTH OF THE BOLTS IN THIS AREA!!!!!! If you look at the "TOP PIECE" innermost bolt hole, What happens is the wrong length bolt get put in the top peice, It goes "through the bottom" and then it makes contact with the head, At this point a "Puller" is created and the more you tighten the bolt the more it "picks up" the flange and t the more it will leak.... Take the two pieces and put them together and thread the bolts in to check that they don't protrude through... If they do and you dont have the right length, just mark it and cut it, no biggie...
The 944 Turbo cooling system operates bypassing the radiator until the coolant temperature reaches 83 °C when the thermostat opens.
So it looks like the Turbo pump only comes on if the engine is off. Therefore I assume that the only way to get coolant through the Turbo while the engine is running is to have the thermostat spring on the hot side of the engine so that it opens when engine coolant temp reaches 82C.
Mike G.
That makes sense then if the electric pump is only for when the engine is off. I flipped the t-stat this morning. That bottom 5mm head bolt is friggin hard to get at with the pump installed...
Im looking at it now and wondering how many beers it’s going to take!
Mike G.
Made a “special tool”. 5mm bit driver into a 1/4 drive adapter. Knuckle joint to a couple extensions. Taped two rare earth magnets so as to not drop the friggin bolt. Don’t forget to elevate the front end to bleed the system.
OK This is VERY and I mean VERY important... PAY CLOSE ATTENTION TO THE LENGTH OF THE BOLTS IN THIS AREA!!!!!! If you look at the "TOP PIECE" innermost bolt hole, What happens is the wrong length bolt get put in the top peice, It goes "through the bottom" and then it makes contact with the head, At this point a "Puller" is created and the more you tighten the bolt the more it "picks up" the flange and t the more it will leak.... Take the two pieces and put them together and thread the bolts in to check that they don't protrude through... If they do and you dont have the right length, just mark it and cut it, no biggie...
I took off the air cleaner and the driver side intercooler tube and it wasn’t too bad to get to. As a matter fact I’m a little disappointed I didn’t even crack one yet.
Mike G
P.S. I went to AutoZone and borrowed one of their radiator pressure kits. This is the first time I’ve tried one of those hopefully it makes a difference. Unfortunately since I swapped out the direction of the thermostat and did a different bleeding procedure I don’t know which one fixed it if it actually does even fix it
Just did a simulated freeway traffic jam run for about 20 minutes about my neighborhood. I think bleeding with that pressure bleeder may have cured the problem. It’s freaking hot out today too 90 deg F. I’m buying one of those for sure!
Just did a simulated freeway traffic jam run for about 20 minutes about my neighborhood. I think bleeding with that pressure bleeder may have cured the problem. It’s freaking hot out today too 90 deg F. I’m buying one of those for sure!
Mike G.
Good to hear, hopefully that clears things up.
Pressure bleeding is just part of my routine every spring.
A coolant pressure tester is a crucial part to have if you own one of these cars and do your own work.
The best procedure after any type of coolant work is to crack open the bleeder screw and leave it open while you are filling the coolant, which helps displace any air in the system. Fill the reservoir to the brim, and then use the pressure tester to pump out any excess air. Once a solid coolant stream comes out of the bleeder, refill the system until it is full and a steady stream of coolant again comes out of the bleeder. Then tighten the bleeder and run the engine with the heater valve open, and only minimal re-bleeding will be needed, if at all.
I work on Porsches for a living, plus I have owned a 951 for over 12 years, and this works every time. For 986/996 and later Porsche cars that have long coolant tubes front to back, we use an Airlift vacuum-fill coolant tool.
.
Pressure bleeding is just part of my routine every spring.
Seriously its the Bomb!! haha
This is how I did it. Cold engine, fill the reservoir a little bit past max. Pump up the pressure, actually no pressure was observed until doing this routine 5 times. Vent the system via the bleed screw quickly (open close fast). You will hear air escaping. Do this until the system holds 10 psi for about 5 minutes. DONE! Well I did actually run the engine till the temp gauge read about to the first line then pumped the system up to 10 psi and quickly opened and closed the bleed screw.
07-13-2019, 05:26 AM
