Hi All,
After about 2.5 hrs I finally got my new heater control valve installed in my '83 944. Post install, the heat now blows hotter than with the original HCV. Additionally, the force at which the air blows is directly proportional to vehicle speed. So at rest, no air blows and on the highway it blows fiercely. Why would this be? I have checked that the heater control lever actually closes the valve so that does not appear to be the problem. Is it possible that it only appears as though it is closed all the way but is still slightly open? If so, would the symptoms I described be the result?
Many thanks in advance for your help

 

Is the symptom cold air at idle but warm/hot with increased RPM/speed?

If so, then you likely have air in the cooling system. At idle the air pocket will accumulate in the heater core but with increased RPM the system will be able to overcome the air pocket and get some coolant into the core.

 

Interesting..I hadn't thought of that. I do know that at idle, there is no air, hot or cold, coming out of the vents (with heater and air conditioning off of course). How does one remove air from the coolant system on these cars? I have had to do this on my newer model cars and there is usually an electronic procedure but guessing it's not that complex on these cars.

 

U can try bleeding with high heat setting and full fan speed, open the radiator cap and resevoir cap. Let car run until it warms up.

But if u have air trapped in the heater core, you will need to flush the coolant system.

 

Are you certain the vacuum connections are intact? What about the vacuum check valve?

 

Check the control flap clips.

 

Thank you both for the advice. I am not sure about vacuum line connections as I am not sure where to look. I am inexperienced to say the least.

Any guidance is greatly appreciated

 

There are no vacuum connections for the early car HCVs, just the late ones. There is definitely some ambient air that blows through the system when you are driving, and I think even new HCVs allow some hot coolant into the heater core, so I don't know if you'll ever completely eliminate the heat. It sounds like you definitely do need to bleed your coolant system, though, so you don't end up with overheating issues.

 

that is definitely true. I remember before the HCV issues arose, there was always some ambient air flow. However, the air now is REALLY hot air. noticeably different than before I changed out the HCV. I will attempt to bleed the system today and see if that changes anything. thanks again for the help

 

Do you still have the red little cap on top of your upper radiator hose that all '82-'83 cars had new ?

Use this as one of your bleed off valves as well as using the guides on Clark's Garage / You Tube videos that Van puts out, or using 944 Online guides on their tech pages.

Simply elevate the nose of the car several inches or more to get the air to purge, bringing the car up to temp, CAREFULLY using the bleeder screw at the back of the block and the little red valve mentioned before, and having the heater valve pushed ALL the way to the right for full open.

It may take several heat/cool cycles to get it all..... some days are easier than others. Some cars are easier than others.

Close the heater control and drive, making sure all the coolant is full in the reservoir and all the bleeder nipples fully closed. Tell us what you find.
Oh, and don't use a cheap anti-freeze or cheap aftermarket radiator cap. Use the specs Porsche recommend for a/f with specific regard for protection to aluminum componentry in the engine and radiator. Get a BEHR radiator cap from Porsche at the correct pound-release rating. Series one cars are different from the series two rating. This will have nothing to do with your heat flowing into the cabin more than likely, but it goes toward longevity to your cooling system and proper ratings for pressure. Ever see photos of those lever release Stant caps in underhood photos of 944 engines ? Well, they don't belong on our cars and many are leaking pressure at the seal for the release as well as the seal around the plastic reservoir nozzle causing heating - cooling issues. Get a BEHR and you have the Best cap Porsche incorporated into this design.

All the best on getting it evacuated from that persistent air bubble.

 

thanks for the great advice. I do have a behr cap that was replaced about 6 months ago. I just performed the coolant system bleeding procedure according to the procedures that you referenced and found them as well, in the Haynes manual. I had to add a fair amount of coolant during the procedure but finally got all the air out. I drove the car into town and it was running much hotter than normal and the radiator appeared not to be able to keep up. when I got home I checked the reservoir and it was EMPTY! Obviously I have a leak but damned if I can find it by sight. Off to autozone to grab some dye.

 

you may well have one if not two or three things going on here:

1- switch for radiator fan not turning on early and holding
2- failing head gasket ( is the car exhaust smoking white or smelling sweet ? )
3- water pump failing ( are there any leaks @ the pump ?)
4- t-stat not functioning correctly
5- both radiator fans coming on in synch and staying on long enough
6- plugged or corroded radiator internally
7- radiator for the heater, more commonly called a heater core, is plugged with aluminum flakes, as well as the coolant passages, due to 'stray voltage promoted galvanic corrosion'. Comes about due to voltage collecting in long term coolant which hasn't been changed often enough. I saw a core plugged so badly with aluminum flakes, not even a trickle was getting thru. Those flakes all got there due to erosion of passageways promoted by stray voltage and old coolant eating away internally.

 

IF the '83 has similar heater control mechanics to the '85 then it is almost certainly the heater flap control clips referred to by Kevin Gross.
These are stupid little clips that (should!) hold the control link rods into the levers on the air control valves on the side of the heater unit (LHS) by the driver's (LHD) right calf. There are lots of posts about this.

 

Nope, the clips are an 85.5+ thing.

 

Do you live in an area with many bugs ?
Mosquitoes or butterflies ? Could also be relating to your lower radiator core fins being clogged as well as the air-con system fins filled with dirt, bugs, and debris.

Minnesota and Florida are horrible for this situation, ( as well as many other humid states ) especially if you like driving in the evening or by lakes. Like I have found out.

You may need to flush and clean with a power nozzle and water, taking care not to bend over any core fins, which would also block air passage.