G'day all,

I might have had a brainwave for a simple, cheap replacement for the radiator pressure tester. Let me know what you think....

This past weekend I flew to Brisbane and collected my new 5-speed '85 Euro, and drove it back to Cairns, a distance of about 1200 miles.

Throughout the entire drive it ran really cool (like, below the lower white line...) until I reached my driveway.

And then, without warning, the temp gauge shot up into the red for several nanoseconds before I shut it down. Ha!!!!

Underneath the car was a puddle of coolant, but I couldn't determine where it was dripping from. You have to keep your sense of humour, don't you?

At first I thought it must be from the front of the engine; possibly from the water pump area. I was immediately suspicious of this because, although the seller had the TB done earlier this year, they hadn't also done the pump. There was a minimal amount of hissing from under the distributor area, but nothing greatly alarming.

Moreover, on wading through the receipts of PO's, I found that one prior had the pump replaced in 2000, so it may be OK.

The next day I checked the TB through the inspection hole over the RH cover: it still looks new. So I refilled the lost coolant, just with water for the moment for testing purposes... It took 5 litres.

When I fired the engine up it idled smoothly, and no water loss was obvious. I didn't bring the engine up to temp, however; I just wanted to make sure that it was nothing easily obvious, and that all was basically well...

I've read through the threads on sudden coolant loss, intermittent loss, etc, and have decided to pressure test the radiator/cooling system before any more serious driving of the new shark.

Now, as most of you probably know, the pressure tester is basically a pump with (in the case of Porsche) a hose leading to a t-junction. You interrupt the hose from the radiator to the expansion tank by inserting the t-junction into the sytem, which keeps it a closed system. See section 19-2 of the manual.

Then you pump it up to about 1 bar (14.7lbs), and go around inspecting all the recommended connections etc for leaks.... No worries.

However, in Oz, such pressure testers are about $150, even for the simpler versions that pump from a radiator cap replacement, which I think is quite a bit to pay for something I might use once in a blue moon...

Now, my idea is this:

What is to stop someone from installing a tyre valve into the top of the expansion tank permanently. Then, whenever the cooling system needed testing, even a bicycle pump would easily inflate 1 bar pressure. A tyre pressure gauge could be used on the valve to ascertain that the correct pressure had been reached...

Such a valve would easily withstand the normal pressurising of the system, wouldn't it? The cap should open between 0.9 and 1.15 bar...

And I can't see that the tyre valve would be affected by the coolant...

What do you all think?

Is it a winner? Or am I a ********?

Now to find the right valve kit and figure out how to install.

I await Rennlist's verdict...

Phill

 

Sounds like a great idea to me. You can get tire valve that will bolt in place fairley simply. I'm suprised no one thought of this sooner.

 

That will work, no problem, as long as you don't mind drilling your expansion tank. As an alternative, tee into one of the small-diameter coolant hoses (believe there's one that leads to the expansion tank along the right side of engine compartment) with some hose barb fittings and a brass tee. You can then thread an air valve into the brass tee. Voila - non-destructive solution.

 

How about splicing a inline fitting into the small hose which runs from the radiator to the overflow tank. It could be a T fitting with a shrader valve

 

Why not pick up a spare $5 rad cap - and drill/tap/epoxy/etc a tube through the top to the spring loaded disc, put a gauge & schrader valve on top - and pump away 'till coolant spurts. If not, I may be talked into cutting a 'tee' into a fill or return hose to the tank, but not the expansion tank.
5l out of 16 is a major loss: didn't the "low coolant" alarm come in? In any event, with a full system, bring the engine uo to temp - the leak should show up without further prompting.

 

I would suggest you take the idea to the next logical step. That idea has two shortcomings I'd want to address.

- Extra point of failure or two... one if you put a metal cap on the stem.
- No way to check leakdown... one of the ways of detecting various internal leaks such as cracked blocks, head gasket issues, etc.

I'm going to take your idea and implement it like this, addressing those issues:

- Tee and short piece of hose; pop small line off of radiator and install this assembly in-line.
- Another tee with a gauge port; this tee is attached to the free fitting on the first tee.
- Gauge on the second tee, maybe 30 lb full-scale.
- Check valve on free port of tee
- Schrader valve(all-metal) on the other end of the check valve.

A pic is worth a thousand words, but I don't have time to draw one right now.

Basically, you hook this thing up and pump it to 1 bar. Then remove the bicycle pump. In addition to looking for coolant leaks, you can see if the pressure indicated on the gauge drops. With nothing more than a Schrader valve on the tank, you will be hard pressed to check system pressure without changing it.

Another advantage to this approach is that you also test the cap as installed on the tank. When finished, toss it in a drawer for next time. If the first tee is relatively large, say 1/2" NPT, you could easily thread different hose barbs on it, say to tap into a heater line on other cars.

Great idea... got me thinking!

 

Well, guys,

seems like this might be a goer...

Yeah, I agree with you all that there seems to be a few alternative ways to incorporate the valve. I'll need to look into which is the easiest, or best, and what stuff is available to me here. I guess the short of it is that there are a number of ways of acheiving an in-system pressure tester...

I don't quite see how the radiator cap could be used to house the valve, because the spring loaded sealing disc would stop pressurising of the system, wouldn't it...?

Garth S: I certainly didn't see any coolant alarm, I can tell you. And I note in various threads on coolant loss that this has happened to a few Rennlisters, and that the first they knew of it was also when the temp gauge suddenly shot up... In one or two cases a following car drew attention to the shark driver that there had been a sudden fluid loss before the shark driver even knew about it.

Apparently the rear heater hose (that short connection to the heater valve) is a classic candidate for failure of this kind...

Any other input by anybody...?

Phill

 

Dave A,

Sorry, mate, I was cogitating and composing whilst you were posting at about the same time...

I agree with you that the idea can be made more complex and used for leakdown as well as just sourcing a gusher. Good adition to the idea, mate...

Phill

 

Funny how viewpoints differ... While my approach requires more parts, it doesn't harm one little hair on my shark's head... a form of simplicity IMHO. I'd be curious to find out how putting the valve on the coolant tank works out. I don't have the cajones to drill into that yellowed old thing... just my luck I'd crack it.

 

Put it into a spare cap.

 

Any ideas on testing the cap?

 

Heinrich,

I still don't understand how it can work to house the valve in a cap. You'd surely have to house it in the lower spring-loaded washer disc, with a big enough hole cut into the top of the metal cap to access the valve, and then perhaps also in combination with a long valve stem also, to service the set-up...

I think interrupting the hose from the radiator to the expansion tank with a metal (or even appropriate plastic - after all, the expansion tank is plastic) tee that the two ends of the hose can be tightened onto is probably the best option.

The central arm of the tee can then simply end in the valve, for simple testing, or lead on to a more 'sophisticated' combination of valve and gauge if leakdown testing is sought...

I think irrigation supply places should have an appropriate tee...

Anyway, Garth, this evening I removed the air filter housing and fired the Beast up and brought her up to temp. A few drops of water did fall under the car, off the front end of the muffler, which seems to indicate that a leak is somewhere at the back of the motor, but I still can't see from where.

From reading other threads, some of which go by names such as "mystery coolant leak" etc, I take it that they can be hard to find, so this pressure tester is a must. So musch easier to play hide and seek with a cold engine and system...

Phill.

 

Both rear rad hose failures I have seen only produced leaks under (more)pressure .

A. Only leaked with increased engine revs. Initial panic thoughts were that it was an Oil burning issue.

B. To start with only leaked just after the normal temperature Engine was switched off. We tested this one and it didn't leak during a ten mile drive and leaked immediately afterward.

Jon
Black SE
Slate Grey GT

 

Interesting idea, hurry and patent it or someone else will!

Although we have different models your coolant dump is very similar to what happened to me. Someone on the list correctly I.D.'ed the problem as a stuck themostat. I changed it, the O-rings
and problem solved.
Even if the receipts show it has been done recently, you still might want to make sure it's in the right direction (common problem?)
Anyway, I hope it is that simple for you.

 

Well, the moment you drill the pressure-rated tank it will IMHO become a bomb and crack soon afterwards. .... with a mod to the cap I think it would be much safer. You could use a cheap aftermarket cap, I've seen US ones with a good pressure release mechanism that appear to be able to take a drill hole in the centre. All I'm saying is, don't do it in the plastic. You could actually even add an inline tee at one of the lower hoses or one of the small upper hoses, and epoxy or crimp your valve stem into that.