fiily

So I pressure bled the coolant on the new to me 944 and I'm finding that heater valve is always under vacuum(closed) and never opens to allow the circulation of the coolant through the heater core and just blows cold air, as the temp gauge continues to climb on the dash. I also have the usual drivers side heater metal clip broken, and the support rod was just dangling so that is the next to do item.

Am I correct in thinking this part in red bold letters is my fix? The vacuum line looked fine, and when I pulled the vacuum hose off the heater valve, the valve opened.

From Clarks-Garage:

The second problem is with the heater control valve. The heater control valve is vacuum operated and located at the back of engine near the firewall. There is a vacuum line which goes from the valve to a vacuum connection at the firewall where the heater hose connections penetrate the firewall. Check this vacuum line to make sure it is connected and doesn't show any signs of cracking. There is another vacuum line fitting near the heater hose connections which goes to a rubber "Y" connector. One side of the "Y" goes to a small check valve attached to the large brake booster vacuum line at the back of the firewall. The other side of the "Y" goes through the firewall to a plastic vacuum retention canister next to the battery. Make sure all these lines are connected and don't show any signs of cracking. If all vacuum lines are properly connected you may wish to remove the heater control valve from the system and check it's operation with a vacuum tester. A problem with the heater control valve opening may also be caused by the vacuum solenoid valve going bad. Remove the solenoid and apply 12 VDC to valve to see if it opens and closes properly. If you look at the picture titled HVAC UNIT RIGHT SIDE above, the solenoid is component #3.

mel_t_vin

As noted, there are two vacuum line connections on the firewall next to the hoses going in to/out of the heater core. The upper nipple is connected to the vacuum line from the brake booster and the lower nipple is connected to the vacuum line that goes to the heater control valve [a solenoid upstream of this nipple applies/removes vacuum for no heat/heat].

Are all of your vacuum lines properly configured?

fiily

I'll triple check and post pics to confirm the vacuum lines are installed correctly.

fiily

So, I went under the passenger side dash and found that the #9 heater valve solenoid(green arrow) is missing the vacuum line(red arrow) to it from the recirculating valve.

The Porsche PET shows this should be connected via a t-fitting from the recirculating air valve.

This might be my issue, can anyone else confirm on a 85.5 that this hose and t exists on their vehicle from the recirc. solenoid to the heater valve solenoid?

fiily

Couple of test performed:

Pulled the vacuum hose off of the heater valve which caused the heater valve to open and got coolant flowing through the heater core and heat in the cabin. I ordered (4) metal clips and supports for the broken support and missing clips this car has, and preventative purchases for any future 944's.

The engine temp is still high even after another bleeding, the temp gauge hovers @ the 3rd white temp hash mark @ idle.



Test #2

I also tested the fan relay and everything tested fine according to clarks garage. The low and high speed fans work via the thermofan switch jumpers.

The low speed fans don't kick in until a tick below the 3rd white line in the temperature gauge.

The high fan speed settings never engaged even @ the 3rd temp line , they only engaged when i jumped the 1 & 3 positions on the thermofan switch.

Should I replace the thermofan switch & thermostat with the 71 deg thermostat and 75 thermofan switch or anyone else have any idea's of what else to test?

StoogeMoe

That doesn't sound too far from normal. The high speed fans won't kick in unless the low speed fan isn't doing its job. It will kick in right about the red zone.

How's the temperature when you're driving? It should be just above the first white line.

fiily

Driving, its at the halfway point, then when I idle, it creeps up to the 3rd line and then the low speed fans kick in. I get a little gun shy if the car creeps anything past the 3rd white line, and shut it down before causing any permanent damage.

Shouldn't my fan's kick in earlier around the 1/2 way mark to drive the temp down to below the 2nd white line? It does so on my 951. I will try swapping the fan relay on the 951/944 tomorrow to see if the relay changes anything on the 944 n/a fan speeds.

mel_t_vin

Below the second white line? Have never seen a 944/2 cooling system, under normal conditions, operate below the first hash, one third, 176* F, mark after initial warm up.

Maybe in Antarctica...

fiily

Pic of the solenoids under the passenger side dash. See the missing vaccum line on the solenoid nipple? The nipple is directly left of the white wire tie.

I also purchased a stant pressure tester and redid the bleeding and found that I had 2 leaks in the cooling system, 1 at the heater control valve, thankfully nothing dripped into the bellhousing/clutch area.

The other was at the radiator neck, both tightened and rebled the system, temp gauge now sits at 1/2 way mark, fans kick in when it goes up and then brings the temps back down to a tick above the 2nd white line.

Seems as if the FLAPS pressure tester is no good for 944's, the stant 270 aka 12270 pressure tester with the A tester is a perfect fit for our cars.

StoogeMoe

See, that's the problem with terminology. I don't consider your picture at the second white line. That's above the first white line. The first white portion is a block, which is where it sits when cold.

But anyway, that's where it's supposed to be when driving along. Right about 82C. Good job to find the leaks. I never like the idea of using a lower temp thermostat/switch unless you live in Phoenix.

fiily

So can anyone confirm the vacuum lines under their dash for me? Still looking for the heater valve fix.

fiily

Fixed it after pulling the amp, head unit brains and glovebox.


The Vacuum lines were not connected via the T to the heater control valve actuator as seen in the pics above. Stereo installer more than likely accidentally pulled the vacuum line from the heater control actuator and put in a spare vacuum hoses that went back into the heater control valve actuator vacuum line when installing the amp and head unit brains for the 944.

Now I have heat/cool controlled from the climate heat **** once again, and installed the new plastic heater rod clasp and metal clip.