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13th December 2019, 13:26 | #1 |
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Excess coolant from header tank
Hi folks, I hope somebody can help with this issue, I parked the car( 2004 1.8t) with offside on the pavement in order to wash it ( two days ago) and let the car idle while I did this. During this time the fan cut in on slow speed ( nothing unusual about that ) for approx 60 seconds and then shut off and I carried on and roughly 10minutes later the fan ( on slow speed) cut in again and a couple of minutes later it went on fast speed . It had sat idiling for 20minutes since I had started so I wasn`t unduly worried, it had now been on fast speed for around two minutes when I parked it back on the drive.Temp gauge remained at 9 o`clock position. I switched engine off and the fan on fast speed continued for possibly another minute then it shut off.I went to the car today and went to do the usual coolant checks etc ( always do coolant check before any journey ) and on starting to turn cap , coolant came out over header tank and area, I didn`t open cap any further and tightened it up again( while I rinsed coolant from the area). I attempted to open cap again and same occurred so tightened it up once again.I tried one more time to remove cap and coolant again came over the top of the header tank and I continued to remove cap completely and coolant was up to the top of header tank.(engine was now of course stone cold).Headgasket replaced in April 2018, done 3k since then, no mayo on oil cap.Any advice appreciated regards Paul
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13th December 2019, 13:56 | #2 |
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That doesn't bode well. There's a significant excess pressure in the cold system, which usually means only one thing. I guess you know that already?
With my 1.8T on stationary tickover, the low speed fan trips on at 104C and runs for perhaps 30- 45 seconds. It turns off at around 97-98C, while the temperature usually continues dropping to below 90C (in today's cold conditions). This pattern will then repeat every ten minutes or so. Your system is overheating, so tripping the high speed at around 112C which continues running for up to fiver minutes after switching off the engine. The excess cold pressurisation can only be exhaust gas I'm afraid. The temperature gauge is useless, staying at 9 o'clock from 75C to 115C. That in itself isn't a big issue in a sound sytem. On cooling down, there would be no excess pressure in the header tank. You can verify these temperatures by checking out the Trip Screen Diagnostic Mode:https://www.the75andztclub.co.uk/for...ad.php?t=55585 TC Last edited by T-Cut; 13th December 2019 at 14:02.. |
13th December 2019, 15:57 | #3 | |
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Quote:
Fred (planenut) |
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13th December 2019, 18:07 | #4 |
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Excess coolant from header tank
Hi Fred, the coolant was checked wednesday am and was ok and it was pm the same day when I moved car to be washed and the issue started.I always keep the coolant level on the max mark.The car is kept on the drive and is on level ground. Just mentioning what T-cut and MG-John was saying, I have always had the hiss of pressure release when I check the coolant level after the vehicle has been left overnight in almost 7 years of ownership and that includes since I had the head gasket (MLS ) and water pump replaced in April 2018 by MJS Auto and Marine after they were recommended by fellow club members. I also replaced the coolant temperature sensor 3 months ago ( again on recommendation of club members ) after the ( unreliable ) temp gauge went down to the 6 o`clock position and fan ran on high speed and it corrected that issue, regards Paul
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13th December 2019, 18:11 | #5 |
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Excess coolant from header tank
Hi Fred, just realised what you meant when you said where do you keep it_____been a long day ! Regards paul
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13th December 2019, 18:48 | #6 |
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13th December 2019, 19:27 | #7 |
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Thanks for your post, at last someone else has confirmed that on a 1.8 you can always have a hiss when removing cap, even after standing for days. Mine has always done this, new mls gasket & head in 2012. No sign of HGF but always a hiss! Was constantly worrying about this, yet my V6 never hisses.
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13th December 2019, 21:24 | #8 | ||
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In fifteen years of ownership, I have never had a significant hiss when opening the cold system. I suspect this 'common' 1.8 system hiss is due to equally common issues with the head gasket/liners. The factory fitted elastomer gasket was never 100% reliable from day one to the day MGR closed shop. And the much lauded MLS wasn't all it was expected to be for many 1.8 engines. Quote:
TC Last edited by T-Cut; 13th December 2019 at 21:30.. |
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13th December 2019, 21:51 | #9 |
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Is the hiss pressure releasing or air being sucked in to a slightly lower pressure in the header tank ?
Kev |
14th December 2019, 08:16 | #10 | |
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The pressure valve system in the cap also contains a hair spring vacuum relief valve that allows air into the tank if required during cool down. Of course air will only be drawn in if any air or coolant was emitted during the engine run. Here's a detailed drawing of the pressure cap in which the vacuum valve can be seen at the top of the central unit. TC |
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