Disco 1 Head gasket fail after serpentine belt broke

Hi, I’ve had the ‘96 300tdi nearly 10 years now and its over heated a few times during that time, shortly after buying it I did a poor belt, expansion tank and hose replacement job and did not properly refill it hence no heater (my fault) and a really bad overheating incident followed, then that was followed by a sticky thermostat and a few more instances of overheating and coolant loss…..and a week ago the (dayco) serpentine belt broke 20 mins from home, the belt only lasted 10 years and 40k km ….poor eh I drove back slowly with no power steering and no obvious over heating BUT later noticed a bit of coolant around the expansion tank BUT I did not check the coolant level after fitting the new belt.

20 mins into the next outing it suddenly went from temp ok (but no heater which I just thought odd) to the temp gauge off the scale, it got home without overheating after waiting for it to cool a bit and then a coolant top up, but coolant was now bubbling fast out of the expansion tank filler cap leaving a trail of water on the road, before settling down to normal (but no heater). Once home, when the engine was started from cold with the expansion cap off I could feel the pressure build up in the tank after a few seconds so I started the HG job. I drained the block first.

I can’t see anything obvious wrong with the HG, and heads with valves cost over $1200 in NZ, I don’t like the idea of getting a specialist to “plane” it flat given that compromises the rocker shaft bearing alignment. I have not investigated where I could get the head tested or how much that would cost.

The HG failed before I bought the car at 200k km (a used head was dealer fitted) it’s done 360k now.

I’m thinking of just replacing the gasket and crossing my fingers, maybe try to diy pressure test the head first in case its cracked rather than the HG failed. If it’s warped it might straighten out when torqued up, well some people think so anyway

Lots of pics attached, anybody see anything that would indicate why the HG failed?

Pic of head

Slap a gasket on it it will be fine, I have done a few head gaskets on 200 and 300 engines and have never once had a cylinder head skimmed, I have also always reused the originsl cylinder head bolts, Iirc they can be reused up to five times
There is a procedure to follow to bleed the coolant system on the 300 TDI
You need to follow this procedure or you will have trouble
Rocker shaft alignment will not be an issue if you skim the head

KiwiTDI said:

Pic of head

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It looks like the gasket has failed between cylinders two and three

lynall said:

It looks like the gasket has failed between cylinders two and three

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Yep, looks suspect, but not the cause of a pressurised expansion tank?

KiwiTDI said:

Yep, looks suspect, but not the cause of a pressurised expansion tank?

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Yes looks like it has been getting through to the water jacket in two places?

Interceptorxj said:

Yes looks like it has been getting through to the water jacket in two places?

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You mean the blackened area on the block surface between 2 and 3….which extends from the fire ring to water holes? See edited pic…

lynall said:

It looks like the gasket has failed between cylinders two and three

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Absolutely +1^
and why did it happen?
COS YOU LET IT OVERHEAT!!!

Absolutely as above clean both faces check head for warping if you wish (costs nothing), new good quality head gasket, and follow tightening and torquing procedures good luck mate

KiwiTDI said:

You mean the blackened area on the block surface between 2 and 3….which extends from the fire ring to water holes? See edited pic…View attachment 276378

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Yes.

KiwiTDI said:

Yep, looks suspect, but not the cause of a pressurised expansion tank?

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Yes it will be the issue, gaskets are funny buggers, and even ones that appear perfect can be at fault.

I know its a gamble but I intend to risk that there is a crack or warpage and just fit a new gasket. I am retired so redoing the job is not a biggie, albeit I don’t want to break down miles from home …..
The existing gasket has held up well to a few overheats, (yes yes some were “user error’) how can tell what type it is? It is made up of thin layers of metal, laminated together with sealant I guess.
Parts prices are higher in NZ, maybe double, and Paddocks freight cost can exceed the value of the parts, but I will probably use Paddocks for the head gasket kit and head gasket itself, plus order a few other parts like hoses, belts.

Paddocks list a “new style”, Elring, and britpart head gaskets, which should I fit?

.

Personally I would avoid the "new style" as its a britpart one. Its possible its a decent make but its a bit of a lottery and I'd rather stick to the elring

Yes, i agree use Elring I use victor reinz or fia, a crack test for the head is about £40 here which i have just started to do now, I also fit new head bolts with every head gasket, are you Lapping valves while its off?

I would go Elring composite, I have never had any issues with one yet.

Yerp, Elring every time!

Elring gasket and a gasket set were delivered last week and today I got the head back on with bolts only slightly tightened, I will torque them tomorrow once I have worked out a diy angle gauge method.

Pic is of the head bolts once I had got them all nicely moving on their threads, a bolt between 2 and 3 was very stiff until worked in and out a few times and maybe this could have caused it to be not done up tight enough last time, some bolts were completely dry of oil.

Other pic shows spots where the head has been eroded, I guess by the injectors firing pattern?

I could get a 004 feeler gauge under the head in the middle in the manifold side only, when trial fitted without a gasket so the head is slightly banana shaped, but just one bolt (very slightly tightened to a few ft lbs) was able to reduce this to trap a 015 (my thinnest feeler gauge) so I reckon it will easily straighten out when 18 torqued bolts are installed….but time will tell.

tyregeezer said:

Yes, i agree use Elring I use victor reinz or fia, a crack test for the head is about £40 here which i have just started to do now, I also fit new head bolts with every head gasket, are you Lapping valves while its off?

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Sorry missed the question, but no I am not lapping the valves, I looked at one exhaust seat and it was perfect so I am leaving it as it is.

Whack it on and it should be fine.
Just remember to bleed the system before you run it.

KiwiTDI said:

I could get a 004 feeler gauge under the head in the middle in the manifold side only, when trial fitted without a gasket so the head is slightly banana shaped, but just one bolt (very slightly tightened to a few ft lbs) was able to reduce this to trap a 015 (my thinnest feeler gauge)

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R U sure you didn't mean 040, rather than 004?!