Mystery disappearing coolant

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Rob B
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Re: Mystery disappearing coolant

#31 Post by Rob B » Sun Dec 20, 2009 1:51 pm

Well, spent a very cold (and snowy) friday changing the waterpump on the car. Job wasnt difficult but it was fiddly and took some time to break the seal of aged muck holding the original on.

Happily, having run the car for ages on the drive there is now no evidence of the jet of steam from the pump that was there before. So hopefully that should cure the problem. Didnt change the rad in the end as the weather was just so bad and it took longer to switch the pump than i'd hoped. I was also wary of putting the spare on as i dont know for certain that its ok, so have put some rad weld in the old one for now as a stop gap and again it seems to have stopped the leak for now at least.

When i checked the coolant level on saturday morning the rad was full but the overflow was empty. I think that was just it settling down tho as im not sure that i completely filled the system on friday night. Also it did say on the rad weld bottle that applying rad weld can cause the level of coolant to drop slightly. Took the car out on saturday afternoon with no signs of trouble, temp gauge bang on half and heater worked perfectly so touchwood all seems well.

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Re: Mystery disappearing coolant

#32 Post by CAR » Sun Dec 20, 2009 6:15 pm

Nice one Rob, lets hope that's an end to it!
Water pumps are not that expensive that a suspect unit should be left unchanged, whilst you search high and low for other possibilities.
Hope you made sure you have plenty of anti-freeze in the old girl mate.

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Re: Mystery disappearing coolant

#33 Post by TedTaylor » Sun Dec 20, 2009 11:36 pm

Huff wrote:Didnt change the rad in the end as the weather was just so bad and it took longer to switch the pump than i'd hoped. I was also wary of putting the spare on as i dont know for certain that its ok, so have put some rad weld in the old one for now as a stop gap and again it seems to have stopped the leak for now at least.
You could use the pressure tester I loaned your parants at the dinner to test your spare rad. Simply block up the hose entry and exits (carved pieces of wood or even ample tank tape will do) and pump it up to about 7 psi. If there is no drop in pressure when left for about about a minute then pump up the pressure a little more - say to 10 or 12 psi and see if it still holds pressure. These pressures are nicely over the normal working pressure of 7 psi but you could go higher if you want to.

However I have to admit that in the days before I had my tester, when I had a dodgy Range Rover rad (core tubes had been slightly damaged) I filled it with water and used an air line to presurise it up to 30 psi. It held and I knew that the rad had to be sound :lol:
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Re: Mystery disappearing coolant

#34 Post by David Withers » Mon Dec 21, 2009 9:10 am

Excellent advice, Ted, but the normal working pressure on the Mk2 is 13 psi, not 7.

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Re: Mystery disappearing coolant

#35 Post by TedTaylor » Mon Dec 21, 2009 5:16 pm

Hi David

I too thought at first that the cooling system pressure was about 14psi and checked my references before making the posting. Just too make sure I have just gone back and checked them all again.

Stanpart Mk1 2000 manual (1st issue) - 7psi
Stanpart Mk1 2000/2.5pi manual (2nd issue) - not quoted, only refers to test pressure being within limits of the cooling system tester
Stanpart Mk1 2000/2.5pi/2500TC manual (4th issue) - not quoted, only refers to test pressure being within limits of the cooling system tester
Autobooks Manual Mk2 (Pub 1978) including TC and S - 7psi
Castrol Maintenance Manual 2000/2.5PI (Pub 1973) - 7psi
Olyslager Manual - 7 psi (13psi later models ....... how late)
There is no reference in the Register Service Notes.
CW quotes 7 psi for Mk1 and 14psi for Mk2

As a matter of interest the Intereurope TR5/6/2500 Manual quotes test at 5psi!!

I thought at first that it would be about 14psi but on reflection 7 psi was quite typical for the 1960s and early 1970s.

Can anyone enlighten on this confusion? :roll:

In my opinion if in doubt 7 psi would be safer - just need to keep a carefull check on the rad level in case water evaporates off but this would happen over a long period of time. If using 14psi and the system is weak or not designed for it, it can lead to excess pressurisation which can cause the system to leak (especially a suspect rad) or the overflow tank system to not work.

Of course if testing then 14 psi will not hurt as it gives a good test for either system

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Re: Mystery disappearing coolant

#36 Post by David Withers » Tue Dec 22, 2009 2:32 pm

Hello, Ted.

That's a good collection of evidence, however some of it is flawed (through no fault of your own!). I've found far too many errors in Autobooks and Haynes manuals, for various makes/models, to rely on them. On the other hand, Olyslagers seem to be quite good on accuracy, and are a handy size for the glovebox.

Olyslager's manual No. 70, published in late 1966, gives no psi figure so far as I can see. A revised version, No. 109 published in 1971, quotes as you said, i.e. 7 psi, with 13 psi "for later models". Use of the term "later models" in 1971 would suggest that 13 psi came in with the Mk2 (or possibly just before).

My 1972 Mk2 PI had a 13 psi cap when bought in 1975 and I can't recall ever coming across a Mk2 with a 7 psi cap (not that I would have inspected every one!).

As you have found, most of the Owner's Handbooks don't quote the system pressure. They didn't start to do so until the launch of the 2000TC and 2500TC, when the pressure was shown as 13 psi.

I think you made a slight 'typo' regarding CW's listing. He in fact lists "13 psi MkII ... or 7 psi Mk1". If any models differ from this, I suspect that the MK1 2.5PI might have had a 13 psi cap. Someone will know.

I believe the lugs on the caps differ between the 7 and 13 psi versions so as to avoid incorrect fitting, hence I'd have thought the radiator filler necks differ accordingly. This would mean that it's important to fit the correct replacement radiator for the system pressure. Does anyone know if this is the case?
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Re: Mystery disappearing coolant

#37 Post by sorbs » Wed Dec 23, 2009 5:33 pm

Dizzy wrote:I believe the lugs on the caps differ between the 7 and 13 psi versions so as to avoid incorrect fitting, hence I'd have thought the radiator filler necks differ accordingly. This would mean that it's important to fit the correct replacement radiator for the system pressure. Does anyone know if this is the case?
I bought a re-con radiator for my mk2 saloon but it had what I assume to be the mk1 style bayonet fitting for the 7p.s.i. cap.

My original mk2 13p.s.i. cap was a little awkward to fit but didn't cause any issues. Eventually, the ancient cap seal started to leak. I got a replacement from Halfords (for a Capri) which fits without a problem.

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Re: Mystery disappearing coolant

#38 Post by tony » Wed Dec 23, 2009 7:24 pm

Over the years I've swapped different pressure caps without problems.As long as the radiator is ok don't see any problem with higher pressure, after all if the radiator is rotten it will leak at 5psi anyway.As all of our radiators are built the same way with top and bottom tanks soldered on, surely extra (13 psi) pressure should not be a problem.The advantage of higher pressure is to raise the boiling point allowing the car to operate at a higher temperature.
Also it pays to check the large rubber washer on the cap.If this does not seal tightly vaccum will be lost when system cools and water will not be drawn back into the radiator from the overflow bottle.
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Re: Mystery disappearing coolant

#39 Post by David Withers » Wed Dec 23, 2009 9:06 pm

tony wrote:....The advantage of higher pressure is to raise the boiling point allowing the car to operate at a higher temperature....
A little off topic, but last week I needed to calculate the water temperature in a steam loco boiler operating at 200 psi and it comes out at a nominal 200 degrees C, or twice the boiling point of water at atmospheric pressure.

That's a nice set of co-incidences even if it isn't applicable to car engines - well, not yet anyway!
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Re: Mystery disappearing coolant

#40 Post by Rob B » Wed Dec 30, 2009 9:46 am

Thanks for all the info. I bought the pressure tester back with me from my parents Ted, thanks again for the loan. I hope to use it today or tomorrow to test the cooling system on the car and the spare rad. Im going to the Triumph show at stoneleigh in early March if that would be a convenient time to get it back to you? If you need it back before then i can always spend a weekend down at the parents (cracking local pub, mums cooking and i can get dad to fit my towbar! hehe).

Good news is that the problem seems to have been solved by the new water pump and a dose of rad weld. Took the car a fair run yesterday and still had all my coolant when i got back. The pump was undoubtedly the biggest culprit but the Rad has definitely seen better days. As its working for the moment i think ill wait a while before changing it.

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