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donmacn



Member Since: 07 Nov 2017
Location: Nth Scotland
Posts: 1557

Pressure testing the coolant system - kit, tips and tricks?
Hey guys,

I have a 300Tdi which seems to be losing coolant somewhere.

The engine and ancillaries are in good fettle; engine professionally/reputably rebuilt 11k miles ago. New radiator. Heater matrix is an alisport and pretty new.

Coolant hoses are silicone, coolant is red OAT.

Car runs perfectly well, no smoke or anything. So, what I’m trying to say is that I think the system is all pretty well maintained and in good order.

At one point there was evidence of leakage from the water pump/hose join - I could see drops sitting on the alternator, but I think that’s stopped now. Obviously the problem is that it’s hard to see stuff when it dries off on a hot engine.

So I’m wondering about investing in a pressure test kit but I’ve never used such a thing.

Any recommendations on bits I’ll specifically need, and how to use it?

Thanks as always

Edit - put in about half a litre tonight, maybe topped it up last about 3 weeks ago. Donald

1994 Defender 300Tdi 110 SW - owned since 2002 - 230k miles and going strong
(The 'rolling restoration' or tinkering thread: http://www.defender2.net/forum/topic58538.html )
2000 Range Rover P38 4.0L V8

in the past..
RR classic - fitted with 200Tdi
1984 RR classic - V8 with ZF auto box
1993 Discovery 300Tdi

not to mention the minis and the Type 2 VW camper...
Post #952908 18th May 2022 9:20pm
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I Like Old Skool



Member Since: 23 Feb 2015
Location: Manchester
Posts: 569

United Kingdom 1994 Defender 110 300 Tdi ST Coniston Green
P gasket. Leaks when engine warms up but liquid is dried away quite quickly by engine heat most of the time. This also fits with you seeing moisture near the alternator.
Mine was the same with erratic minor coolant loss. Hasn't lost a drop since I fitted my own home made card gasket about 18 months ago Thumbs Up
Post #952928 19th May 2022 12:55am
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Mossberg



Member Since: 29 Feb 2020
Location: Lancs
Posts: 315

United Kingdom 1993 Defender 90 300 Tdi HT Aintree Green
I thought the 300tdi used the blue coolant - ethylene glycol based (blue) antifreeze.

I would welcome people to correct me but I have a niggle telling me that the OAT stuff does not work well with some components in the 300tdi, but I can't remember what they were or where I read it!

I changed my coolant early last year and I am sure I would have preferred to use the OAT as it was a 5 year change interval compared to 2 years with the blue. I used a 50/50 mix off coolant/distilled water when I did mine.

Sorry, didn't mean to go off topic, but thought it was worth raising this just in case it is an issue.

Good luck finding the source of your coolant loss and I hope its a simple fix.

Mick

PS - I have a feeling you can't mix the two coolant types but again I can't remember why!
Post #952931 19th May 2022 8:05am
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donmacn



Member Since: 07 Nov 2017
Location: Nth Scotland
Posts: 1557

Thanks guys,

In order:
P Gasket - it could very well be. I know it's no guarantee, but that's as "new" as the rest of the work. The stuff dripping onto the alternator was actually coming from where the hose goes onto the water pump body - directly above the alternator. It wasn't a 'jubilee' clip, but one of those Mikalor T clamps. I nipped it up a few times, and it seemed to have stopped - but as I say, hard to tell when coolant dries off. I'm now a bit unconvinced by those clamps and looking to change them.

OAT coolant - you are right that it was orginally the blue glycol based stuff that was in it, and that you can't mix them. Does one or other of them go like a jelly? I've also read about the supposed unsuitability of the OAT stuff for older engines, but my local guy supplies it and I do trust his experience.

So back to the pressure tester. I've never used one, or seen one used. There's always youtube, but presumably someone here must have done this. Do I need to get one with a thread/diameter that matches the expansion tank, or is it put into the system elsewhere?

Is it as simple as connecting it, pumping up the pressure, and looking for leaks? Donald

1994 Defender 300Tdi 110 SW - owned since 2002 - 230k miles and going strong
(The 'rolling restoration' or tinkering thread: http://www.defender2.net/forum/topic58538.html )
2000 Range Rover P38 4.0L V8

in the past..
RR classic - fitted with 200Tdi
1984 RR classic - V8 with ZF auto box
1993 Discovery 300Tdi

not to mention the minis and the Type 2 VW camper...
Post #952945 19th May 2022 12:31pm
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Mossberg



Member Since: 29 Feb 2020
Location: Lancs
Posts: 315

United Kingdom 1993 Defender 90 300 Tdi HT Aintree Green
A friend did my timing belt and we did the water pump etc at the same time. He used one of the kits which I think screwed on the expansion tank. He pumped it up and it had a gauge so you could set the pressure. Once at pressure you watch the gauge to see if the pressure drops. If it remains stable your system is good, if it starts to drop you look for leaks.

I would look on youtube for a demonstration to be honest. As mine didn't show signs of leaking we did not have to go around testing.
Post #952947 19th May 2022 12:46pm
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