300tdi split expansion

The expansion tank on my 300tdi defender split two weeks ago. I replaced it with another second hand one today, took it for a test drive, got home and it's split again. I had the head tested and the gasket was ok. The only thing I've noticed is with the expansion tank cap off if I Rev the engine it bubbles in the tank, I'm no machinic so don't know if that should happen. Or if it was a dodgy tank again. Before I go a buy a new one is there any thing else I should check.
Cheers.

Did you replace the expansion tank cap also.
Who tested your head gasket and what did he test as sounds more head gasket for that sort of pressure.
Is the car overheating on temp gauge

It was sniff tested and didn't change colour. To be honest I'm not sure if I used my original cap or the one that came with the second hand tank as they got mixed up. I left it on tick overdoes a good 30mins didn't move above half way on the gauge. And I'd didn't move during the test run of about 30minutes.

bubbles in tank is not good. BUT, you'll need to know where its coming from. Its probably the head gasket. But if a sniff test is clear, then where is this air coming from ? has it been bled properly ? water pump seals Ok ?

There only bubbles when I Rev the engine. I was thinking exhaust gases so head gasket. But the sniff test was clear. I think I'll take it to a friend of mine see if he's got a sniff tester. Is there anything I can do to check the gasket?

Classic 300 head gasket failure normally due a very slight weep from the back of the timing chest right behind the alternator this allows the level to drop over time the engine gets hot and there goes your gasket, this may have not happened in your ownership and the leaky P-gasket may have been changed but the damage has been done.
Only way to be sure is head off and get it tested properly by an engineering firm, use a quality gasket Elring etc.
The P-gasket is about 2 quid.

I carry a 12 volt soldering iron, it's been used to plastic weld a split 300 expansion tank in the past, successfully. Just thought I'd say, like ..

Thanks 4 that Disco 1BFG But as we /well most of us know when you get pressure 9 times out off 10 it's the GASKET that's BLOWN !

Steve

Magicgrotto said:

Thanks 4 that Disco 1BFG But as we /well most of us know when you get pressure 9 times out off 10 it's the GASKET that's BLOWN !

Steve

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me not understand

I've never seen bubbles in the exp tank come from anything but a blown HG - but I was giving him the option of the 0.00005% of the times when its them Klingons getting all cranky

And the "like" was agreeing with you

I forgot them bloody klingons

Disco1BFG said:

And the "like" was agreeing with you

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Twoz for the LIKE you plonker !

So it looks like the head gaskets gone. While its off is there anything else I should change or check?

Look down the pushrod holes and see if the brass bits of the tappet itself are nice and round and not egg shaped, the head bolts can be used up to 5 times iirc.