Help, 300tdi overheated, now poorly.

[ChrisM_110]

Caveat: I'm not that au fait with diesel engines, be gentle.

On Sunday my new thermostat [from a blue box] failed shut, and the engine hit 120ºC in seconds, as I was going up a long hill with a 3 door 110 rear tub on the roof rack.

I shut the engine off within 20 secs, coasted to the side of the road, had a swear, and shouted at the RAC for sending a Transit to suspended tow me,

then waited 2 hours in temperatures that were melting the waxoyl out of my rear door frame, by the side of the M5 for a flatbed.

The engine boiled most of it's water immediately, and steam appeared to be escaping from the back of the head, I'm not sure as there was a lot of it, as the expansion tank cap did it's thing as well.

Today I replaced the thermostat, natch, retorqued head bolts [all were fine], checked water pump, water was clear of oil, oil was clear of emulsion.I then ran it up to temp.

It sounded fine, no more rattles than normal, thermostat [an 88º wakstat not another unnamed blue box job] opened and closed as expected.

However, when actually driving and under load, rather than sat there revving away warming up, at anything over 25% throttle there's a lovely new rattly tappety noise.

What have I killed?

[Guest]

Silly question I know, but have you checked the oil, level and condition? if it got hot you may have cooked the oil and need to flush it and give it something to smoth the rattles..

Jason.

[ChrisM_110]

Never thought to do that, and it did look a bit thin and smingy, I was just checking for signs of head gasket failure to be honest.

I'm more worried that as it appears the new rattle in engine load related it might be big end, but I'll do a full oil change tomorrow, thanks for the tip.

[nicks90]

you have blown the head gasket,

the steam escaping from the back of the head nearest the bulkhead is the clue. On the 300tdi the head gasket often fails there and instead of venting coolant into the oil, or oil into the coolant - it just vents to the engine bay (which is nice, as it does less damage).

so you need to whip the head off i'm afraid.

if you are lucky, it will just need a new gasket. If you are unlucky you will need a head skim. If you arre really unlucky you'll have totally warped the head and need a new one.

Bottom end should be ok though.

[Les Brock]

Errr....

How did you recheck the head bolts ?

correct sequence is..

The first torque setting is to 'set' the bolts, so 40nm on all of them

Tighten all 60-deg

Tighten all a further 60-deg

Then bolts numbered 1,2,7,8,9,10,15,16,17, and 18 a further 20-deg.

The head bolts can be reused, but if you are unsure of the history of the engine, then it's wise to replace them

Agree tho that the head gasket has gone, get the head checked to make sure its still true, you dont want to put it all back together to find it doing........

[mmgemini]

Do you have the standard temperature gauge fitted ? Then the "normal" temperature could have been 95Deg C. The 300Tdi boils very quick.

I suggest you take the head off and pull No 4 piston. Then you might find some damage. Sorry.

[ChrisM_110]

Thanks for the replies and help.

Head gasket to do tomorrow then. Bum.

Mike: it's a non standard gauge fitted by the previous owner with a Kenlowe, I'd say it was fairly accurate.

When you say pull No 4 and look for damage what exactly am I looking for?

[steve b]

.....a bent con-rod , with the head off turn engine over andd check each piston is rising to the same hieght at tdc , any that are lowerr would indicate a bent con rod . Generally if the rod is bent it won't come out up the bore ........

hth

Steveb

[mmgemini]

Damaged piston and bore. The bore should glaze bust. I didn't see the damage on my daughters Discovery but she needed two pistons after hers blew. They built the engine then get the tap so it had to come apart again. It must be worth a look so you don't have the job to do twice.

[ChrisM_110]

Cheers boys, more news tomorrow after some work, thnks again.

[adam300Tdi90]

I would suggest getting a sniff test first surely? An overheat doesn't necessarily cause the head gasket to blow, I'm with Jason in saying that the oil could just be cooked, causing the tappety noises?

[ChrisM_110]

Well, I'm fairly sure there was steam escaping from the back of the block, but there was steam arsing about everywhere so I'm not 100% sure.

I'm planning on head gasket, inspection and oil change tomorrow afternoon, and a quick prayer too.

[nicks90]

it certainly wont do any harm to change the head gasket as a precautionary measure anyway,

you boiled the engine, so its well worth doing even if it hasnt leaked! Even if its just to make sure the bores and stuff all look good, doesnt hurt to have new gaskets at the top end either and to reseat all the pipework etc. Think of it as a bit of major maintanence