Pete Lewis Posted June 1, 2022 Report Share Posted June 1, 2022 you need to have a pressure test on the coolant side there are rad caps out there with a integral pressure gauge woulld show a loss of pressure very cheaply and others like like Link to comment Share on other sites More sharing options...
Sandy Gibson Posted June 1, 2022 Author Report Share Posted June 1, 2022 Pete I looked at that test kit earlier but couldn’t see how it plumbed in. Would it screw into the drain cock beneath the manifold? I have seen rad caps with temp gauges but none with pressure gauge. Any idea who supplies? Thank you Sandy Link to comment Share on other sites More sharing options...
johny Posted June 1, 2022 Report Share Posted June 1, 2022 It goes on the radiator overflow connection and Ive done it before with a bicycle floor type pump but dont put in more than 1 bar... Link to comment Share on other sites More sharing options...
Sandy Gibson Posted June 1, 2022 Author Report Share Posted June 1, 2022 Thanks Johny Is the overflow pipe not above the rubber seal on the rad cap and therefore not part of the pressurised system? Do you test with the engine running or pressurise the system by some other means? Thanks Link to comment Share on other sites More sharing options...
johny Posted June 1, 2022 Report Share Posted June 1, 2022 youre right its above the rubber seal but the rad cap has a small valve that is to allow coolant to be sucked back in from the reservoir bottle and using the pump youre going to apply air pressure in to the rad through that. This method does require that the cap has a good top seal as well as the lower rubber one but this should be ok if the system was working correctly before... Youre going to simulate the system pressure produced by the engine being up to temperature but without having run the engine. Using the air to apply pressure to the whole system you can leave it as long as you like and because the engine is already cold the pressure should stay stable unless you have a leak somewhere. You musnt apply too much pressure as obviously the radiator cap cant lift to release it so you could damage something.... Link to comment Share on other sites More sharing options...
68vitesse Posted June 1, 2022 Report Share Posted June 1, 2022 Had a similar problem with my 2L Vitesse early in January, following advice on here turned out to be water leaking from rocker cover studs. Tested by removing rocker studs and gently applying air from my compressor to radiator overflow pipe, radiator cap on, got quite a fountain. Changed oil and filter and remaining coolant in oil soon evaporated as engine warmed up. Best of luck with your problem. Regards. Paul. Link to comment Share on other sites More sharing options...
Sandy Gibson Posted June 1, 2022 Author Report Share Posted June 1, 2022 Thanks for that. A good outcome, hope I get as lucky! Link to comment Share on other sites More sharing options...
Duane Posted June 9, 2022 Report Share Posted June 9, 2022 On 31/05/2022 at 16:16, Sandy Gibson said: Just fired up my mk3 engine after rebore. All went well, good compression, water circulating but when I checked the oil it’s very milky. Also bubbling through the rad with the cap off. Thinking of taking the head off, getting it skimmed and trying again with a new gasket. Does anyone think this should be the way ahead? Alternative is to pull the engine and I haven’t really got the time (or the enthusiasm at the moment!!) to do that. Any advice would be much appreciated. Thanks Where you based, if head is off I can check out for you, if warped etc, we have engineering shop at my company and as said before to members happy to help where I can, it's all about favors etc Cheers Duane Link to comment Share on other sites More sharing options...
Sandy Gibson Posted June 17, 2022 Author Report Share Posted June 17, 2022 Back from holiday and finally did a pressure test on the cooling system. First I drained the oil and used a new rad cap. Took pressure up to 7lb and it dropped back to zero in about 10 seconds. What I don’t understand is that there were no visible leaks and no water is draining from the sump. Also, and very strangely, after the pressure goes back to zero and I take off the rad. cap the water level seems to have risen! I’m thinking there might be a big air lock in the system (air compresses, water doesn’t) and that might explain the increase in water level and also air is escaping causing the pressure drop? Still no further forward in explaining my real problem of water in the oil. Really struggling with this one. Anyone got any more thoughts? Link to comment Share on other sites More sharing options...
johny Posted June 17, 2022 Report Share Posted June 17, 2022 Did you say the compression test results are still good? Link to comment Share on other sites More sharing options...
Sandy Gibson Posted June 17, 2022 Author Report Share Posted June 17, 2022 They were fine. The engine was running really well. I’m guessing that pressure dropping to zero in 10 seconds is a significant leak and is more than I would get with a blown gasket. Link to comment Share on other sites More sharing options...
johny Posted June 18, 2022 Report Share Posted June 18, 2022 Wonder if its worth draining the cooling system and re-pressurising with air to see if you can hear a leak? Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 18, 2022 Report Share Posted June 18, 2022 a rapid loss it possible the leak back is from poorly seating rad cap thinking of the simpluze a garden hose on a heater pipe might show a leak the trouble with mayo is just changing the oil will re contaminate with any residue remaining in the sump/block etc could the oil be the problem ??? just thinking Pete Link to comment Share on other sites More sharing options...
Sandy Gibson Posted June 18, 2022 Author Report Share Posted June 18, 2022 It was old (but unused!) oil I used for toe initial start up as I intended draining it soon after I had done a few miles to settle everything in so. No sign of any contaminant when I put it in so don’t think that’s the problem. I did wash the engine down weeks before re-assembly but blew all the chambers out with compressed air plus it was rotated many times on the engine stand so I’m sure there was no water trapped anywhere. used a new rad cap for testing and polished the filler cap faces to try and guarantee a good seal. Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 18, 2022 Report Share Posted June 18, 2022 so now its in the hands of the Gods ha ! Pete Link to comment Share on other sites More sharing options...
Iain T Posted June 18, 2022 Report Share Posted June 18, 2022 1 hour ago, Sandy Gibson said: used a new rad cap for testing and polished the filler cap faces to try and guarantee a good seal. I have two rad caps, one seals the other doesn't it's a lottery! Try fitting a second seal from an old cap on the radiator at the bottom of the filler neck. This seal should maintain pressure and my super shiny stainless steel cap didn't! Iain Link to comment Share on other sites More sharing options...
johny Posted June 18, 2022 Report Share Posted June 18, 2022 I think at that pressure loss rate some soapy water round the cap would show if its the source.... Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 18, 2022 Report Share Posted June 18, 2022 Oohh!!! Bubbles love it Pete Link to comment Share on other sites More sharing options...
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