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@rogerstopford : I think this is a part that can also be sourced from vendors for the 928. Take a look at 928sRUs or 928 International; they should have parts available to help get you back up and running.
Anyone know which way the coolant flows at the hcv? Towards the front of the car or the back? My new hcv has a flow direction arrow but the old broken one does not.
thank you. The Four Seasons 74671 alternate part is a different physical layout than the original equipment, and puts the vacuum line at 90 degrees to what it was. I'm waiting for 000.830.57.84OEM Control Valve - Brand: OEM I also ordered from Paragon to compare.
The whole point is to get something different than OEM due to the weakness of that part. But to each their own. I have the 74671 on my 968 right now and have used alternative heater valves in my P cars for over 20 years.
The OEM style can split and dump all the coolant in seconds, this can be dangerous to motorcycles as well as leaving you stranded.
Hi, thanks for your continued dialog on this re HCV. When I got 74671 I noticed it has a flow arrow on it which is why I asked about flow direction. I figured the flow was actually the other way, going towards the front of the car. Because the rubber gasket/seal in the valve in the broken HCV I removed is on the side of the valve towards the front of the car. I attach a pic of the old/broken HCV and the 74671 HCV. As you can see in the old/broken HCV the rubber valve seal/gasket is on the side of the HCV closest to the front of the car, and if the flow is towards the firewall then that pressure is actually pushing the flap off and away from the rubber seal, which is weird. If the flow was going the other way, towards the front of the car, then the pressure would be pushing the flap onto the rubber gasket/seal, which would seem like the right thing. Could you post pic of your installation?
I recommend using the OE valve and not one from a Ford Escort. OE is the important part of that statement. Most of the premature failures are with Meyle or URO copies of the original equipment. The valve from Porsche is expensive but Mercedes use the same valve and are more reasonable in cost.
On a 968, the valve is located on the suction side of the pump so flow within the transfer tube is toward the front.
The theory put forth about pressure on one side of the valve is not really true. Considering the system is a loop, with only one valve, the valve prevents flow but would only have a slight pressure difference between sides.
I've had issues and only with the OEM valve. Granted they last a while but honestly a better design is better and one less thing to worry about. A cheapo knockoff of the OEM valve might be worse but honestly slightly less crappy crap is still crap.
I'll get some pics of my installation when I take the car out this weekend, not much to see really. A heater valve, vacuum line...
I get it if someone wants to run the OEM valve, it's probably OK if replaced every timing belt or summat.
OEM is often confused with OE. OEM generally refers to the manufacturer while OE refers specifically to the part. I believe the current requirement for a manufacturer to claim OEM status is that they manufacture any part for any automobile maker. The valve that Porsche sells is OE and will last 20 to 30 years.
I think I've seen them fail as early as 15 years in-service on a 16v 944, the location near the exhaust manifold is not kind to this design. Service life is a consideration but my main issue with the poorly designed OE valve is how it can fail by splitting in half like an Oreo cookie and dumping all your coolant over god's green earth in seconds. Or more likely making a very slick spot on the road.
As per Roger / OP's note about the gasket, I did not explore why but I had one fail on a 928S4 by internally leaking coolant through to the heater even when closed. Constant heat. The internal sealing might be another shortcoming of that style valve.
Thank you for the responses. Flow going forwards, towards the front, would have the coolant flow pushing the actual valve plastic thing down, onto the rubber seal gasket, which would seem right to me. It makes a difference because the substitute part has a flow direction arrow on it, whereas the OE part does not.
I recommend using the OE valve. OE is the important part of that statement. Most of the premature failures are with Meyle or URO copies of the original equipment. The valve from Porsche is expensive.
But inexpensive compared to a destroyed engine...
Originally Posted by Gage
The theory put forth about pressure on one side of the valve is not really true. Considering the system is a loop, with only one valve, the valve prevents flow but would only have a slight pressure difference between sides.
Correct. The water pump does not "pump" coolant, it only circulates it. Very little pressure is created by this.
Originally Posted by Gage
OEM is often confused with OE. OEM generally refers to the manufacturer while OE refers specifically to the part. I believe the current requirement for a manufacturer to claim OEM status is that they manufacture any part for any automobile maker.
To my knowledge, this is correct.
Originally Posted by Gage
The valve that Porsche sells is OE and will last 20 to 30 years.
Considering that one of my '93s still has the original valve with over 80,000 miles, this is indeed possible. However it is pushing things a bit and a reminder that I need to change mine before it splits.
I guess maybe Clarks Garage settles which way the coolant flows through the heater control valve - as per the Clarks Garage pic below, the coolant flows from the HCV to the heater core, so the coolant flows from the HCV towards the rear of the car. At least for 944 and I would guess 968 is the same. So that means the alternate part, which has a flow arrow on the outside, fits in the same way as the OE, which is good.
Perhaps the diagram should be titled "normally aspirated 8 valve 944 cooling system". The cooling system of the 16 valve (S2 and 968) has the HCV located on the cold side of the heater core. Flow direction of the system is the same.
06-25-2024, 10:07 PM
