heinrich

And actually, you don't need to pressurise the tank permanently so just have a cap that is very plain, with a valve stem for when you want to pressurise, and otherwise use the stock one.

Big Dave

Just a note: when my water pump was leaking (at least initially), I couldn't determine the source. Each morning there would be about 1/2 cup of coolant on the garage floor. Nothing would drip during the day while I was at work. It seemed the engine had to cool down overnight before the drips would start, and then it wouldn't happen all the time.

I pressured tested the system, and still nothing came out even though it was done with a cold engine. I still to this day can't figure out why the leaks only happened overnight and then couldn't be forced with the pressure tester. My only suspicion is that the leak must have been very slow and I didn't pressurize the system long enough for the leak to actually make it self evident. Even a mechanic couldn't find it. He told me it was a head gasket

That leak behavior continued for nearly a year. Then, within a short two week time period, the flood gates opened. By the time I replaced the pump and TB, it was losing almost 1 gallon per day!!!!! No need to look for the leak at that point....it was all too obvious....the pump was leaking from the bearing (the gasket around the pump housing was still working).

Good luck!

Jim bailey - 928 International

If you have a bicycle pump perhaps you have a tube ?? cut off a piece with the valve and hose clamp it on the reservoir in place of the radiator cap (cover the overflow hole). pump it up some check pressure with your tire gauge , you do have a tire pressure gauge !

heinrich

Something tells me Jim has a brown .... no, a very very brown bicycle ....

TroppoShark

Well, after work yesterday I fired The Beast up and went for a drive of about thirty kilometres (twenty odd miles...) to give my sweetheart her first ride in it, and to see how such a drive would show up in the leak dept.

The temp gauge didn't rise abnormally, and the coolant warning light didn't illuminate' but when I checked the overflow tank it had lost about a litre, although there was still about an inch of fluid in the tank.

Checking under the car there was a drip from the back of the engine somewhere...

So, I've ordered a replacement hose from the engine block to the water heater control valve, and a new valve as well, and am going to change both of these first, even though I couldn't see any drips from them the other day when I had the air filter box off. Oh yeah, and a new rad cap.

I suspect that I'm going to go ahead and renew the thermostat as well, because I have no papertrail proof that it's not the original... Greggles, thanks for confirming that idea in my head.

Jim B, that idea of the quick test using the bicycle valve still attached to some tube may be the easiest fast to perform. And yes, I do have the original Porsche tyre pressure gauge (in my '84 A/T shark it was still in the sealed plastic bag in the spare tyre well: unopened!)

Heirich, for the life of me, I still can't see how to incorporate a vale into a rad cap, because of the problem I outlined earlier, that it's not just the top of the cap that needs piercing, but also the lower sealing washer/disc. How do you propose overcoming that? I'd really like to be able to use rad cap set-up, beleive me, but I think it would have to be an entirely different design cap to allow access to the valve which has to be housed in the lowest part of the cap...

Big Dave, yeah, I can't beleive how frustrating trying to find a leak can be. And all the time there are those fears in the back of the mind: head gasket? Potential catastrophe waiting at the water pump/TB? Coolant injecting into the engine? God, where does it end until that leak is nailed and the mind put to rest...

Jon928se, I haven't fully defined what category my leak comes under yet. I'll temporarily file it under 'intermittent unresolved angst-producing mystery latent gusher...'

Thanks to everyone so far for the suggestions and pointers. I'll post back as I make progress. The worst thing is that I probably won't have Beast ready for the Cairns Porsche Club meet this Sunday. Grrrrrrrr.....

Phill

heinrich

Phil, just buy a cheap aftermarket rad cap and make a silicon plug that reaches down to seal the tank. in fact you could use the stock one (spare) and delete the spring. Once it's twisted on it will seal the opening with the silicon. Then (with it out) drill straingt through, instal a valve stem and be done with it. You could instal the valve stem first and then add the sealing silicone.

TroppoShark

Just a PS: it was the hose from the rear of the block to the heater control valve... I replaced both of these, although simply tightening the 'worm screws' may have done the job... but it might not, too.

Meanwhile, that pressure tester idea is out there....

Phill.

marton

While searching for possible cures for my radiator leak, I found this thread.

I have a tire pump which I bought for circa 20 US in a local supermarket. It runs off the cigarette lighter and has a digital gauge (both bar & psi) and you preset the pressure you need. It switches off when it reaches the desired pressure but continues to measure the pressure. It also came with a variety of connectors.
This was ideal for radiator testing. I took the small pipe off the expansion tank (the one that comes from the top of the radiator) found a connector that plugged into it nicely, set the tire pump pressure at 14.5 psi (written on the expansion tank rad cap), plugged the hole from the expansion tank (the plastic cap off one of the probes on my multimeter was a perfect fit) and switched on. It worked great, as a side benefit I found that the rad cap started to lift at 13.5 psi which I guess is in limits.

The leak was in the rubber seal betwene a side tank and the core; now I just have to find a rad shop that are willing to bet their reputation on bending those little aluminium clips....

nc_growler

Just rigged up the simple pressurization system that worked great.

Removed hose a nipple on radiator and plugged.

Attached 12" length of 1/4" ID air hose to nipple and clamped. Inserted Schrader valve (with brass connections to a burred connector and clamped. Two short pumps with a bicycle pump and coolant shoots out of the weep hole of the water pump...

Only 1500 miles on this new waterpump too. Time to tear it down and replace. Thank goodness for the TB/WP thread!

https://rennlist.com/forums/928-foru...re-w-pics.html

Mrmerlin

NC what kind of pump did you install on your car was it new or rebuilt??

jpitman2

Anybody who has a Motive pressure bleeder has the pump side of things, complete with gauge.I like the idea of splicing a fitting permanently into the small hose from the header tank, but to remove the failure point of having a schrader valve there permanently, maybe it could be removable and the hole closed with a plug? I will look into what there is available in the way of schrader fittings.
I replaced my header tank a couple of years ago with a locally made alloy unit, becuase the RHD 927- units are up over A$600 here. Such a tank could easily and safely have a hloe drilled and tapped for a valve IMHO, but I dont really want to remove it just now for this when there are simpler ways to do it.
jp 83 Euro S AT 52k

dr bob

Connect to the system through the radiator vent hose, using a T and a stub of hose plus a few clamps. It's 8mm hose, 5/16" hose and barbed fittings.

nc_growler

MrMerlin - The PO installed a new Laso aftermarket waterpump. No reason to expect it to fail... I guess it just had a manufacturing flaw?

Still under warranty. Thinking about simply replacing. Sharkskin suggests I take extra steps and have Obehave "beef it up" before installing it.