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Head gasket blown? - odd symptoms


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Hi All,

I'm trying to work out what's up with my 300tdi defender...inconsistent symptoms :

Has always lost water with no obvious signs of where from (I've owned it for 10yrs and have always had to top it up)

It loses just under 2L of water in around 150miles or less, then stops losing it and will run at that level for months without issue, until I think about it and top it up again.

Occasionally billows loads of white, steamy smoke on startup (not necessarily when cold) for 30s to a minute, then clears.  This only seems to happen when it's wet weather - either raining hard or foggy!

Never gets over 1/2 hot on the temp gauge, even when I was towing a heavy trailer last week.

Doesn't seem to be losing power, although as I said, it's always lost water since I bought it, so maybe it's always been down on power!

No troubles starting.

When I checked this morning there was some slight mayonnaise on the filler cap, which is the first time I've seen it, but nothing on the dip stick.  I have topped the water up twice in the last week due to the towing, so it's got through a lot more water in a short space of time than it usually does.

No signs of oil in the water.

Any thoughts?  Are the smoke and water loss related?  What else can I check to narrow it down a bit more?

Thanks,

John

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Hi. 

I would take the manifolds of and have a look for a "steam cleaned" port. I had the same symptoms for the same amount of years and put it down to a bad hose. One day it began to smoke white on initial run and I took the head of. Already at the manifolds I could se that one of the exhaustports didn't look like the other three (clean...). The port had a small crack so the water went into the exhaust and probably always had... a new head cured the drinking problem ?

/mads

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Mads' advice is very good.

It does sound like an internal failure between water system and bores.  It might not be reaching then oil system at all (that would take quite a large failure).  The fact that you see condensation on humid days is an indication of high water content in the exhaust.  What is slightly perplexing is that it stabilises for a while, then drops quite quickly again.  If it loses water when conditions are pretty cold, but loses less or none when its warm, then that all points to a crack that is sealing up with expansion from warmth.

The mayo on the cap could just be condensation, especially if it's limited to the cap.  It'd be worth removing the rocker cover with the engine cold to see if it's widespread.

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Thanks Snagger,

To clarify, the water drops quickly to a pretty consistent level (just under 2L down) and stops there, it seems to be happy at this level for months and never gets over half-hot.  I'm starting to wonder if the two are unrelated - looking on various forums there are lots of reports of white smoke in wet conditions for all makes of vehicle, and these are generally put down to normal condensation in the exhaust.

I'll top up the water again, let it idle for a while and take a really good look for leaks.

Thanks for confirmation on the cap mayo, I was hoping someone would say it's not that unusual!

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That reliable stabilisation of water level 2l below normal suggests a leak, internal or external, that the water is escaping through under gravity and sopping once the coolant level reaches the leak.  The pressure in the coolant running could close the leak, or it could be sealing up when running with thermal expansion, or it might just be a very slow leak that doesn't lose much fluid in the short time it's driven, but the continual slow loss when parked is cumulative and allowed to develop of extended periods.

 

Are your foot wells wet?

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20 hours ago, Bowie69 said:

Sounds like P-gasket...

A leak from there would lose about 2l, I suspect, depending on where on that gasket the leak occurred.  Not that easy to see externally, either, in a crowded and dark area, with a black painted block not helping show leaks either.  A very plausible (and frequently guilty) suspect!

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Thanks all...latest update...I topped up again and checked everywhere, no sign of a leak on the P gasket, hoses or anywhere else.  Was towing again at the weekend, 100 miles, seemed to be fine, bit of a struggle on the hills (reasonably heavy box trailer), but cruising at 60 on the motorway without issues.  On checking the coolant after, it had dropped about 1cm in the tank.  Topped it up again before the drive back (not towing this time), again driving fine, cruising at 70 with no problem, after about 45mins I pulled in to the services, left the engine running and had a good look around, still no signs of leaking anywhere.

So I think it must be the head/gasket, hot or cold, there is no sign of an external leak.  It's booked in on thursday to have the head off and inspected, so I'll let you know what happens.

 

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Phew, glad that's confirmed, could have been very embarrassing :blush:

On the top of the tank it says something like 'Fill to the mark indicated', but the line around the tank looks like a seam from the tank being made in two parts, rather than a fill mark - so I'd say it's not that clear which 'mark' they are referring to.  There is also a post in the tank which appears to be at about the same level, so could be that as well!

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  • 2 weeks later...

I had this exact same problem with my 300Tdi - as it wasn't giving blown head gasket symptoms, I posted on here asking for help. After about 10 replies saying it was my head gasket, a very helpful fellow suggested that it might be a blocked anti-siphon valve (near the header tank). I replaced it and the associated tubing for just over twenty quid. That was the best part of ten years ago now, and it's not troubled me ever again!

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2 hours ago, cackshifter said:

Anti-siphon valve? Is that the little widget in the middle of the 3 small pipes on the offside?  

 It is. If you go for pattern part it is cheap enough to have a go to see if it makes a difference:

 

http://www.brit-car.co.uk/product.php/208464/0/bleed_pipe_assy_expansion_tank_300tdi_defender___discovery_1

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