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Last edited by tino04 on 25th Apr 2023 1:41pm. Edited 1 time in total

Your head gasket seals the channels between oil, combustion and cooling. Depending on where your head gasket has blown, you'd either get water in your oil or if it's blown between combustion and cooling, you'd most likely be getting exhaust gases in your expansion bottle.

Remove the cap and see if there's a fair amount of pressure released and look on the inside of the cap for sooty deposits (although more different to see with petrol vs diesel). If you have none of those symptoms, purchase a sniff tester - they're less than £15 and will give you an immediate answer.

If you haven't got white sludge in yout oil or on the cap or water in the oil and the test results for the coolant are negative, I'd be fairly confident it's not your head gasket and would instead be looking inside your V around the thermostat housing and injectors. The white smoke is a little bit of a mystery. 2015 Range Rover Autobiography 4.4 SDV8

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Last edited by tino04 on 25th Apr 2023 1:41pm. Edited 1 time in total

In which case this would lead me to think it's your head gasket.

I had a 3.6 TDV8 previously with similar symptoms. No white smoke or contaminated oil but always loads of pressure in the expansion tank (coolant disappeared, low coolant warning comes on, remove cap, loads of pressure, coolant returns but below minimum).

I think to confirm in your mind definitely get yourself a sniff tester and then you know exactly which avenue to follow:

https://www.ebay.co.uk/itm/124375564723?mk...media=COPY

In terms of other maintenance whilst the heads are off, probably fair to assume it's worth replacing any o-rings on the oil cooler and changing the thermostat housing, in addition to the chain. 2015 Range Rover Autobiography 4.4 SDV8

Ah well. Thanks Gary.

Anything else I should look to get done whilst she's in bits on the garage floor?

Seen your edit! Thank you

Last edited by tino04 on 20th Oct 2022 8:26am. Edited 1 time in total

First step


Get a scan tool on it and see which cylinder is given you issues, it may still only be a dodgy coil pack. The mechanic has only changed a plug moved a coil pack, and up a water pump change thus far.

As Gary says get a sniff test on it as well, its normal for coolant to run back into the expansion when you remove the cap when its hot, check the coolant hoses by squeezing them for excess pressure though.

Good luck, it is VERY unusual for a head gasket failure without a big overheat occurance, hopefully you'll be lucky

Cheers Dingg. This was more where my head had been, particularly your last sentence. It's the same cylinder that's flagged this time too.

A sniff tester is cheap so, for the sake of £12, you can confirm or rule out in your mind before embarking on a job for £xxxx which may not be the culprit so, well worth having! You also get enough fluid for around 20 tests so, good to keep safe somewhere and test any car you need to in future. 2015 Range Rover Autobiography 4.4 SDV8

Ordering now!

I believe that there is a small pipe under the Supercharger that perishes with heat. Worth checking the Jaguar forums for information on service and faults and fixes.

I have exactly the same engine with exactly the same fault. Loosing coolant, 'restricted performance' msg, running rough and steam out of the exhaust.

It was the right bank head gasket. But the head gasket failed because the coolant crossover pipe that connect the two heads had failed and leaked coolant, causing the heads to overheat and subsequent gasket failure. it also warped the heads.

I've had the engine rebuilt. Including the front end timing gear and supercharger coupler upgrade whilst at it.

Although I'm currently waiting for a replacement transmission.

Let's hope that this will be the end of my woes because I love driving this 500bhp plus monster truck! 2010 L322 5.0l Supercharged

2008 L322 Vogue 3.6 VDV8 (The wife's)