Hi all, just a simple question after this simple explanation...

Changed the head on my tdi 300 less than a year ago after the gasket blew. Ran OK after a good test run including a return trip to the UK, with no loss of coolant after a 1000km+ run. However, Unfortunately the radiator plug blew out a few weeks ago and I had to tow it back home...

I can start and drive the Disco, but almost immediately ( 2 mins) the coolant 'bubbles' in the expansion tank - is this normal? I thought that a blown head gasket was a little more subtle and would probably overheat and 'bubble' in the expansion tank after about 15-20 mins?

Could it be somthing simpler, like a buggered water pump?

Not a happy bunny.

Harold 4x4 said:

Hi all, just a simple question after this simple explanation...

Changed the head on my tdi 300 less than a year ago after the gasket blew. Ran OK after a good test run including a return trip to the UK, with no loss of coolant after a 1000km+ run. However, Unfortunately the radiator plug blew out a few weeks ago and I had to tow it back home...

I can start and drive the Disco, but almost immediately ( 2 mins) the coolant 'bubbles' in the expansion tank - is this normal? I thought that a blown head gasket was a little more subtle and would probably overheat and 'bubble' in the expansion tank after about 15-20 mins?

Could it be somthing simpler, like a buggered water pump?

Not a happy bunny.

Click to expand...

I had something similar, my radiator blew and within 400mtrs the temp guage into red. Had the system tested for gas in coolant, result, yes gas evident. Had head removed, pressure tested, luckily only gasket blown. Have had head skimmed due to a slight warp. YES bubbles in coolant system indicative of gasket problem. My own fault, should have changed radiator instead of feeding rad weld.

Unfortunately for you I think the head will need to come off again, these TDI engines are so "precious" about their cooling systems almost any transient excursion into the hi temp zone of the all but useless oem guage will mean a head gasket blow. And this is almost guaranteed if you use a resurfaced head along with pre used head bolts, (not sure how your engine was repaired last time). As my mate, a long term TDI owner and expert repairer of the marque said, "once that gauge is heading to the red, the head gasket is already fubared".
I have fitted a cooling system level monitor along with a capillary type direct reading gauge to the top of the thermostat housing, and I still am very cautious. about any minor temp deviations.

I used a brand new head with new bolts, which is why I'm surprised it has blown again...

Pretty sad really, with all the correct stuff done to have the head gasket blow again.
Does the pressure build quickly in the coolant header tank and not just with temperature? If the header tank pressure pumps up really quick from cold that would be a good indicator that the gasket is leaking, it's also possible to have a check for combustion gasses in the coolant done at a workshop.

Hi Harold, couple of questions - what make was the gasket, who made the bolts, were the dowels in good condition and both fitted OK, were the head bolt holes in the block clean and dry before you refitted the head and sorry, but I have to ask, was the block and head so clean you would have eaten your dinner from it?

You must identify the cause of the overheating in the first place.
A 300tdi is actually overcooled for the UK environment in standard form assuming all parts of the lubrication ( oil ) and cooling system (water) is standard and fully functioning ok. That is one way how it survives in hotter climates. Not loosing any coolant is an indication that things are OK but it is NOT definite proof !!! .
Oil is primary a lubricant but is also a coolant, water is only a coolant all be it a very important one ( means / medium of heat transfer)

Your temperature gauge should always be below the mid point even in the hottest British summer, and at the worst never go above the mid point even if worked hard towing up hill in a traffic jam etc. I expect France to be warmer, but you should never get above mid point

Get your engine sniff tested and pressure tested at a garage and that will tell you if you have exhaust gasses in the coolant -----blown head gasket, and a pressure test will confirm if you have any leaks anywhere----------- blown head gasket but also other problems

A blown gasket is the most likely but there is a chance of a crack in the head or possibly block

Regards
Jonathan

discomania said:

Hi Harold, couple of questions - what make was the gasket, who made the bolts, were the dowels in good condition and both fitted OK, were the head bolt holes in the block clean and dry before you refitted the head and sorry, but I have to ask, was the block and head so clean you would have eaten your dinner from it?

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Yes to eating my dinner.
Yes to all bolts being spotlessly clean and dry, and dowels good.
Gasket? Standard 3-hole as I've always used, can't remember the make.

In this particular instance I've lost motivation. Thanks for the responses, but I am now going to 'cannibalise' this Disco and reanimate my other 3-door 300 with the spares.

Gazbo said:

As my mate, a long term TDI owner and expert repairer of the marque said, "once that gauge is heading to the red, the head gasket is already fubared".
deviations.

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I agree but I've had my 200 TDI flirting many a time with the RED ZONE in Morocco in the height of summer due to a F-Off winch bumper restricting air through the radiator and got away with it