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Rabbitwabbit



Member Since: 31 Mar 2021
Location: Blackpool
Posts: 38

United Kingdom 1997 Defender 110 300 Tdi CSW Stornoway Grey
300TDI - weird coolant issue
Hi all, I have an intermittent coolant problem which is driving me insane! I check my fluids weekly and before any long runs and the coolant level has always been spot on to the level marker in the header tank. I also have a Webasto thermotop C fitted which I use daily. I use a 50:50 mix of red antifreeze.
A couple of weeks back I had 2 issues. One morning the Webasto failed to warm up the vehicle (Very grumpy wife on a cold morning!!), but I put it down to me possibly setting it wrong, but the vehicle started normally and ran perfectly. The second issue was a couple of days later when I took the vehicle for a 15-mile trip to my mates and I heard the expansion cap hissing a little – something I’ve never noticed before!
When leaving my mates after 3 hours I checked the header tank and the coolant level was much higher than normal – i.e., it hadn’t gone back to its normal level when cold. I started the engine, ran it for 1 minute and re-checked the coolant which had now returned to normal.
Everything was fine for a couple of days, then I checked the level again and once again the level was much higher than normal! It’s as if an air lock is occurring somewhere in the system which then prevents the Webasto from firing up properly due to the air lock.
Another weird thing is when I removed the filler plug on the top of the thermostat, then the higher water level in the header tank did not drop to fill the thermostat housing.
I have no coolant leaks; the vehicle runs spot on temperature – whatever the load or length of run (Completed a 200-mile run with no issues) and the heater works perfectly.
The issue with the Webasto has occurred on a couple of occasions since – which coincides with the higher coolant level in the header tank – when the coolant level is normal, the Webasto works perfectly.
Any ideas??? ----------------------------------------------
1997 Land Rover 110
1981 Range Rover Monteverdi Design Study
1974 Range Rover
1959 Series 2 (Now sold)
1971 Range Rover (Now sold)
1973 Lightweight (Now sold)
1981 Range Rover 4 door (Now sold)
1957 Series 1 LWB (Now sold)
1973 Range Rover (Now sold)
Post #980631 31st Jan 2023 11:15am
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MarkBrown



Member Since: 03 Oct 2022
Location: Mid Wales
Posts: 475

Wales 1983 Defender 110 Other HT Auto Keswick Green
Sounds like head gasket leak to me, pressurising system causing air lock.
Post #980638 31st Jan 2023 11:43am
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Rabbitwabbit



Member Since: 31 Mar 2021
Location: Blackpool
Posts: 38

United Kingdom 1997 Defender 110 300 Tdi CSW Stornoway Grey
Thanks Mark - that thought had crossed my mind. There is no additional evidence to suggest this - no oil in the water or water in the oil. No weird smoke from the exhaust, the vehicle starts and runs sweetly with no issues. I cannot feel any 'blow' from the back of the engine and the head gasket was done appx 4000 miles ago and has been perfect since. On my 200 mile run to Wales and back it sat perfectly happy on the Motorways and A roads - and when I checked the levels everything was perfect. I run 15 miles up the road and see the issue - run 15 miles back and no issue. Just last night I checked the levels and it was over full and it had just been pottering around town - been out this morning and just checked it now and it's perfect. Rolling Eyes ----------------------------------------------
1997 Land Rover 110
1981 Range Rover Monteverdi Design Study
1974 Range Rover
1959 Series 2 (Now sold)
1971 Range Rover (Now sold)
1973 Lightweight (Now sold)
1981 Range Rover 4 door (Now sold)
1957 Series 1 LWB (Now sold)
1973 Range Rover (Now sold)
Post #980667 31st Jan 2023 2:03pm
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90roy



Member Since: 21 Jun 2016
Location: Middlesbrough
Posts: 130

United Kingdom 
It does sound like a head gasket. Same thing happened to mine almost exactly as you described it. 300tdi 90 1996.
Post #985337 12th Mar 2023 10:25pm
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Rabbitwabbit



Member Since: 31 Mar 2021
Location: Blackpool
Posts: 38

United Kingdom 1997 Defender 110 300 Tdi CSW Stornoway Grey
Cheers 90Roy, I've just changed the radiator as there was a small weep towards the top of the rad and it couldn't be repaired so whilst everything was drained down I decided to do the head gasket anyway. Worryingly there was no evidence of head gasket failure around the head or the gasket - but everything is now cleaned and put back together. Early tests are positive - so time will tell if it's actually resolved the problem. Fingers crossed. ----------------------------------------------
1997 Land Rover 110
1981 Range Rover Monteverdi Design Study
1974 Range Rover
1959 Series 2 (Now sold)
1971 Range Rover (Now sold)
1973 Lightweight (Now sold)
1981 Range Rover 4 door (Now sold)
1957 Series 1 LWB (Now sold)
1973 Range Rover (Now sold)
Post #985339 12th Mar 2023 11:06pm
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