grepin

After a search I didnt find much. Whats the best process to bypass the heater. Just plug the outlet from the engine and inlet to the Y pipe. Or loop the two. I might as well remove the control valve all together as its new and wont be needed until I fix the core.

FredR

You have to block coolant from escaping the block so the valve is an effective way of doing that- I simply disconnect the vacuum line, undo the actuator arm and wire the actuation lever in the closed position. Beyond that I made a hose connection from the valve outlet back to the coolant system to close the system once more. You also need to close the now temporarily redundant vac line. The only time I operate the valve manually is when filling the system with fresh coolant.

My heater was fine I just do not use the heater over here.

GregBBRD

.....The heater control valve is far from water tight.
You will need to make a loop, bypassing the heater core, completely

grepin

Exactly what I am thinking. No need to keep the heater valve involved. It actually gives me room to move if removed. I guess you guys are not picturing a RHD set up either...should have mentioned the difference. Pic to show my plan. Or just blank the two ends. Blank outlet from the block and blank inlet to Y pipe where the core returns. Is there argument against that. Only thing I can think of is it would get pretty ugly if one popped off under pressure. . But thats really what the CV is doing. Happy the Vac line will need to be closed off. Thanks for the replies. Yes if you noticed I am still not happy with my little bent fuel hose. I know you run a keen eye over things Greg. Its new but not ideal. Thinking about getting a bent fuel pipe made up at a brake place and using two short rubber pieces to connect. But thats extra connections. I digress..

FredR

The valve is a unidirectional disc valve with a spring designed to close the disc and when the system is pressurised the force applied further assists sealing albeit the differential pressure component is going to be very small or so I would think.

The valve is not designed to be a tight shut off classification but for sure will seal way tighter than most middle age men! For sure one should not rely on the valve and leave the other end open to the engine bay- that would be rather dumb ***! I actually tested a new valve with 15 psig across the disc and it held tight [to my surprise] but as they age and with heat quite conceivable they will leak a few drops here and there but that is operationally irrelevant- obviously Porsche thought they were tight enough.

In my case I did not want to leave the cooler with stagnant coolant and possibly risk corrosion damage thus I took the core out of the loop. The hoses going to and from the cooler thus have to be interdicted be interdicted and thus joined together at some point. They will be flooded and pressurised but there will be no flow in that part of the system. On my LHD system I did this just behind the 1/4 bank.

The nuances of achieving such are a bit different in your case because of the RHD configuration but the process configuration is identical. If you are hell bent on removing the valve altogether there is no harm in that either - you just have to achieve a positive isolation either side of where the valve was- my point of view was why create an additional problem to solve when the solution is in front of your eyes but then I have a new spare valve and new hoses in my parts bin for if and when I ever want to reinstate the heater circuit.

grepin

Got it thanks. I will consider leaving the valve in. However the core is coming out all together as it leaks......eventually.

FredR

Do you really need the heater in Adelaide?

Pulling the HVAC unit is quite major task- probably one of those things that looks intimidating but after one has done it does not seem as bad as one first feared! As long as the ac evaporator holds I can work around other problems. I had my blower motor bearing crap out on me last year so I pulled the bonnet off, removed the motor from above and then pulled the recirc flap assembly with a view to replacing the actuator [easy] and resealing the flap- that is almost impossible! Herman wrote a procedure for this that requires what is tantamount to major surgery to get the flap out and work it some. I removed the unit from my late S4 after it was wrecked and to be fair the job was not too bad. Whether i would have got it all back together again and working that is another matter altogether.

grepin

Nah probably not. However I intend to pull the dash anyway to refurb and do the instrument cluster as well. I might as well do it if I am that far. I also need to get the aircon working. Now I do need that in Adelaide. I may end up in there anyway. I have already done a full intake refresh including timing belt and WP change myself. I am sure I can work it out. I got the car as a non runner and now its back on the road. Sadistically I enjoy working on it somewhat more than driving. Maybe not quite....

FredR

The 928 is a bit like the Forth Rail Bridge in that it takes the repair crew about 10 years to paint it end to end then they go back to the beginning and start all over again!

dr bob

If you look at some of the assembly-line pictures from back-in-the-day, you'll see how car assembly starts with a guy with a heater core in one hand and the evaporator in the other, walking into the first assembly station. As he continues, people start bolting stuff to them until there's a whole car ready to go. Pretty impressive process. Know that accessing those parts is pretty much the reverse. Start unbolting stuff until all you have left is the heater core and evaporator. Grab the replacements, then follow the original factory process to put the car back together.

At least it seems like that sometimes....

GUMBALL

Here is a "sidebar" question:

Can you install a shut off valve between the outlet at the back of the head and the heater core ?? Thinking of "hot summer days"
Will that cause other issues ??

GregBBRD

You do understand that the OP has a leak in the heater core and needs to completely isolate it from pressure?

GregBBRD

Leave it in, take it out....completely moot once the heater core is completely abandoned and both ends disconnected.

I bypass leaking heater cores on a frequent, temporary basis, until it is convenient (both for my shop and the client) to take them out and replace...generally incorporating other needed work.

On left hand drive cars, the heater control valve, sans heater core, just makes routing the hoses more complex (and provides two more places for leaks to occur), so I remove it until we replace the heater core.

grepin

Thanks Greg.

Is just blanking it the wrong thing to do. Obviously at the block and at the Y pipe. Or is looping it better. Either way is just as easy.

FredR

A puzzling comment from your good self- as someone who had to seal highly toxic well heads at 10,000 psig for a living to avoid killing everyone within a 40 mile radius [amongst many other things] I think you can safely assume that I understand the heater core needs to be isolated.

The OP asked how it was done and I explained in principle how I did it and why- in my case it was to preserve the heater core as I never use it. The layout on the RHD models is somewhat different but the principle remains the same. If there is any confusion I will happily post a pic of what I did.