Diesel Head Gasket – hard to replace?

[Miles69]

Well, it looks like the dreaded has finally happened to our Bongo. My wife returned from a family trip with water blowing out of the header tank. The temp gauge was OK but the cooling system was pressurised.

I’m going to fill the system tonight and bleed it just to make sure. I’ll also check to see if any smoke comes out when I start her up tonight and also check to see if there are any other leaks on the cooling side of things that may be causing air to get in the system. However, I’m pretty sure the gaskets gone as I’ve seen it all before with some of the old wrecks I’ve driven.

So, how hard is the head gasket to replace on a diesel? How much time do I need to allow for the job and will I need any specialist tools? I’ve rebuilt mini and old ford pinto engines so I’m sure I can cope with the removing the head and changing the gasket, but, I’m just a bit worried about having to mess with the turbo and injector bits …

I’ve got to the change the gasket myself as my wife is on maternity leave and I need to save the cash as I’m due to be made redundant in January.

[Simon Jones]

There's a factsheet in the members area which should be enough to get you thru. Don't forget to fit new cambelt & cylinder head bolts. I can't recall exactly which size sockets I needed, but you will definitely need 10, 11, 12, 13 & 15mm. The two 'tricky' ones are deep sockets to remove the injectors (although you may get away with leaving these in place) and something big enough to fit the crankshaft pulley bolt. You need to be able to turn the engine two revolutions as part of the cambelt tensioning process.

I would also recommend getting the head pressure tested whilst its off & then consider having it skimmed. Expect to pay about £60 for each of these, but at least you'll know the head is sound before you got to the expense & effort of refitting it.

Have a good read up of posts on here - most of the answers any queries you have have are buried in here somewhere.

You may find some useful info in these two posts, especially about 'decking the block' & Wellseal:

http://www.igmaynard.co.uk/bongo/forum/ ... =+wellseal

http://www.igmaynard.co.uk/bongo/forum/ ... =+wellseal

[Miles69]

Thanks simon. If everything went to plan just how long could you do the whole job in? A day? Hillside have quoted me £900 plus VAT for an exchange head to be fitted. Bongobits have got new blank heads for 475 plus VAT (or 650 including all the gaskets etc). Prices vary so much for a new head I'm now really confused as to what it could cost ... I'm praying i find a leaking hose tonight

[Miles69]

Well, spent a while bleeding the system tonight and checking for leaks. System seems to bleed up OK and there are no leaks, and no bubbles coming up to the header tank. However, i cannot get the bottom radiator hose to heat up, doesn't even get warm when revving the engine and getting the fan to kick in. Even after driving down the road with the temp gauge up the hose didn't get hot.

The water in the system seems to be brown with a fine silt in it so I think that its a blocked rad and I guess the bubbles coming up last night were due to the water boiling after its long journey. Going to order a new one as I'm sure its blocked. I just hope that i haven't blown the head in the process. Fingers crossed.

[Simon Jones]

Sounds like you may be lucky . Give the system a good reverse flush & consider getting a new thermostat too as it could be stuck. I would suggest you re-fill with plain water first & bleed the system thoroughly. If the van runs ok for a few trips, then drain & re-fill with a 50/50 mix of anti-freeze.

Taking the head off is the last resort, so eliminate all the other options first. I guess you could do it in a day, but it's hard work & it's not worth trying to rush it.

There seems to differing opinions on how hot the bottom hose gets. On mine, when the van has got up to temp & been stationary for a long while, then the pipe is almost too hot to touch. If you've been driving & then stop, there will have been a good flow of air over the rad, so the bottom hose may be cooler.

[Bob]

If possible use distilled water to stop scaling. Good luck.

[Miles69]

Well, I'm a bit confused now, removed and tested thermostat, and checked flow on radiator. Radiator seems good and flow is good on a back flush with a hosepipe. Back flushed rest of system and removed all crud - water seemed very dirty but no blockages The thermostat does open but only in a pan of boiling water - I think most stats open between 70 and 85 degrees C - so I’m inclined to think that the stat may be faulty as the pan water is definitely boiling as it opens. Going to fit a new stat, fill, bleed and test. Fingers crossed.

[brorabongo]

AFAIK it's 82 degs that the stat starts to open at.

[Simon Jones]

When you get your new 'stat, test it in a pan of boiling water with the old one. It will test the new one does open & you'll probably see the new one opens sooner, faster & wider than the original.

[dandywarhol]

Better to test it in a pan of warm water and bring it up to temperature with a thermometer in the water - that way it'll show exactly when it opens rather than too late.
It should start to open between 80 and 84 deg. C and be fully open at 95. It should also open at least 8.5mm

[Miles69]

Thanks for your replies guys.

Well, now I'm totally depressed, fitted stat, bleed using funnel method, went for a drive in rush hour traffice. Everything was OK. Then I went for a 35 mile drive and everything was still OK, no overheating, all heaters working and radiator fans working. After a few hours returned to the car, checked the coolant, water level still good, no loss, and started to drive home, happy I'd fixed it. Four miles down the road and disaster strikes. Overheated and lost coolant. Three hours later the bongos on the back of an AA wagon. Going to rebleed this morning - I just don't understand - surely if the head gasket had gone it wouldn't have gone 40 odd miles with a problem? Can't find any other leaks. It does look like its the head ...

[daveblueozzie]

take the expansion cap off, then take the radiator cap of slowly to make sure there is no air trapped, when water comes out of radiator replace cap and refill expansion tank.
when you bleed the system and refill are you turning the heaters/air con on full, back and front in the bongo. when you feel hot air coming out, let it run for a bit then turn the engine off, let it cool ,check coolant, if its not moved ,run again and keep checking the levels. it may be necessary to re-bleed to try to get the air out.
leave overnight and then check the levels again you will probably find its gone down a bit.
you have probably done all this. but it might help others.