Nicole

So, as a preventive measure I'm planning to replace all my rubber hoses on the car this year. And I thought I'd be clever to upgrade to an all metal heater valve while I'm doing this.

Now, I just did a "dry run" of connecting the hoses with that Audi 5000 valve, and it looks like the hose that goes to the theater is getting really stretched out a lot.

The below picture shows the long and short hose - it's the long one that connects at the top of the valve that I'm concerned about.

Is it safe to stretch the hose like this, or am I running a high risk of it failing at this connection?

Of course, there will be hose clamps when I install it in the car...

ZEUS+

A problem that occurs, is that the hose splits when clamping.

Nicole

What should I do - use the plastic heater valve instead?

ZEUS+

928 motorsports has a valve that will work. There are other valves that will work. I can search if you want.

dr bob

Nicole-

Only you would take the hoses to the theater before installing them. Adds a touch of culture to the whole project, I think.

On the stretching issue, the hoses do in fact need to stretch a bit when installed. In a perfectly-fitted hose world, the hose would have most of tension from stretching before a clamp is applied, so the clamp wouldn't have to gather much of the circumference before applying the force needed to keep the hose from sliding off. It would be pulling gently on the reinforcing material as it's stretched too. Most hoses that are a bit too large will leak when clamped as they gather under the gear. The harder you tighten it the more likely it is to leak, too. So slightly smaller hose is really just right. Is it just stretched over the end of the end of the nipple there, and just snug on the rest of the diameter where the clamp goes? If so it may be just right.

In the meanwhile, take a look at the existing hose and how it fits on the heater valve while it's still in the car. I'm not close to my garage (a few thousand miles away...) or I'd go look at the old/spare heater valve with a caliper to confirm the nipple size on it for you.

Have fun at the theater!

Bill Ball

Others report using this valve. I wonder what they did.
https://rennlist.com/forums/showthre...A+heater+valve
I remember looking at the 1983 Audi 5000 valve at NAPA and concluding the fittings were wrong. NAPA has another metal valve, but only the housing is metal - the valve itself is plastic. I've stuck with the OEM valve. My first one lasted 15 years.

ZEUS+

It is best to find a proper fit. To much stretching makes the hose weak. Add some heat and pressure, then if the edge of clamp cuts in. Seen this too many times. Ok in an emergency.

Nicole

OK, so here I am a bit confused...

I'm looking at the thread Bill linked to, as well as the heater valve page on the 928 Motorsport site - and like my Audi 500 valve, all the valves pictured have the same diameter input and output.

Howevr, the hoses I have are not the same diameter. The short hose from the block to the valve is larger in diameter than the hose that continues from the heater valve to the heater box.

I have not removed my factory valve, yet, so i don't know what the connectors are like on it. Does the factory vavle have a larger ingoing and smaller outgoing connection?

The latter would make sense given the hoses I have (all original Porsche parts), and possibly explain why the short hose between block and valve sometimes goes "bye-bye"....

Nicole

LOL!

Actually, I looket at this and thought it might be much easier to install an "assembly" of the heater valve with the two hoses, than to install the pieces individually (you know, German process efficiency).

I also needed to find out which direction the heater valve would have to be installed.

But when I put them next to each other I noticed the discrepancy in diameter between the metal valve and the hose to the heater. That's what got me worried, and I stopped right there.

I hate nothing more than to start a project on the car and get stuck in the middle of it...

the flyin' scotsman

the OEM valve works when new although I followed Tony's direction re. 'no heat'.

I took a further precaution and glued the valve closed.

The electrical outputs from the HVAC controller can be used for more recent applications; stay tuned.

Nicole

So, I guess, the verdict is that this famousu Audi 5000 valve is a "no go"...

dr bob

Nicole,

I did the 'replace all the hoses' chore a couple summers ago when I did the last TB/WP project. Don't remember problems with the hoses on the heater valve, but I just used a factory valve so no relationship to your dilemma. I figured that the original valve was replaced at 10 years old as prophylactic maintenence, then that one was replaced at about 8 years old for the same reason. So far no signs of failure on any of the three valves that have been in the car. So should I chase down a metal replacement that may or may not fit and may or may not fail unexpectedly?

The next heater valve I put in will be a "fail closed" type, and I'll whip up a little diode and transistor circuit to reverse the action of the solenoid. Or just add another solenoid between the existing one and the valve, energized whenever the key is on. Key off, valve is isolated with vacuum on it so it stays closed and no heat-soak of the AC airbox. I would like to keep it real simple though, however it gets done. I have the heater valve tied closed still, even after I replaced the actuator diaphragms that were leaking and causing the water valve to stay open. It's OK except for those arctic LA winter mornings when the temp drops down into the 50's overnight. Brrrr! It's usually OK by mid-morning when it's on it's way to a 70 degree afternoon, though.

IcemanG17

Nicole
It works just fine......I've had one in mine for a year with no problems.....one other bonus is its bi-directional so you can't install it backwards......the only issue I had when installing it is the nipple that the vac line attaches too is a shade smaller than the plastic valve...so it leaks....but a tiny zip-tie fixed that!

Bill Ball

Yes, the valve fittings are as you describe.

Podguy

Replace the hose from the motor to the valve with a silicon hose. It will last much longer. You can pick them up at a local parts store. All of the emergency vehicles are now being fitted to silicon hose for increased relaibility. The hose between the heater valve and the motor is one of the most common failure points in the 928. Other hoses that commonly fail and should be replaced with silicon hoses are the cross over hose from the front of the engine to the metal Y pipe and the hoses running from the metal Y pipe to the overflow tank.

Porsche tried to stay away from too much metal in the cooling system for a reason. If you look at the steel Y pipe it is very common for them to rust and corrode even when there is adequate cooling fluid in the system. The dissimilar metals cause reactions and can lead to failure. Plastic is electrically neutral.

Dan the Pod Guy