Whats going on with my TD

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Jaba
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Whats going on with my TD

Post by Jaba »

Got some funny symptoms and I think it might be HG time - or maybe not (he said hopefully)

Put a replacement engine in last year. A recon unit with 25K use, or that is what I was told. Everything is sprayed silver so it probably is.

I have done 2000 miles since then. Its not really using water but I have topped it up once. But even when the engine is cold when I take off the rad cap to look in the header there is pressure release and the sound of gurgling and bubbles of air coming up. The rad cap is a good one swapped from another BX. It is as if the coolant has turned to champagne and is slowly releasing its pressure.
All hoses were new last year. The car runs very well, does not overheat, although as previously posted uses a bit more fuel than expected.

So why worry. Well sometimes after starting up the low water light comes on and off a couple of times in the first few minutes of running. It always goes off initially after starting. The water level in the tank seems to vary more than it should as well even allowing for the a higher level when the coolant is hot. And there are signs of water on the outside of the header tank even though the tank is not overfilled.
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Post by jeremy »

Sounds like additional gas getting into the cooling system from somewhere - and if its at pressure - its the head gasket.
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Post by DavidRutherford »

Sounds like it's not a headgasket to me, just some air in the system somewhere that hasn't bled out properly, causing merriment with the coolant level and making gurgling noises when you remove the cap.

After all, if the HG was leaking, I wouldn't expect the cooling system to be able to hold pressure overnight.
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Post by mountainmanUK »

As a fellow TD owner, I concur with David.
Sounds very much like there is some kind of airlock somewhere in the cooling system. TD BXs are notorious for being a pain in the a$$ to bleed properly.
When I refitted the rad in mine last summer, I thought I had got all the air out, only for the cooling light to come on, and all the other symptoms you are getting, after around 100 miles of motorway driving. I pulled off the M6 and proceeded to re-bleed the system again, which worked fine. Since then I haven't even needed to top up the water in 9 months!!

Using a cut-down pop bottle (suitably sealed to fit the expansion bottle) will help when bleeding, as will giving the hoses a good 'pump' with a hand to help dispel air from the bleed screws.
You can also loosen the temp gauge switch fitted into the thermostat housing, to give you an extra bleed point. That was what finally cured my airlock!

Good luck!
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ken newbold
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Post by ken newbold »

Have you checked that the rad is getting hot/warm all over?

Could be the rad that's blocked and restricting the circulation (he said hopefully) [-o<
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Jaba
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Post by Jaba »

Thanks for the ideas. The rad is a new(ish) one and there is no overheating showing on the temp guage.

I dont think its air even though the symptoms might point that way.
Today started up the engine having removed the rad cap thus releasing the pressure and left it off. Almost immediately out of the header tank wafted smoke/ steam in a continual flow. It looked very artistic as it drifted upwards and away like letting the genie out of the bottle. Didn't get my three wishes though.

This is bizarre. Could it be a cracked head ?
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Post by docchevron »

Jaba wrote:
This is bizarre. Could it be a cracked head ?
Could be, or it could just be the gasket, or it could be a porous block, they usually go in number cylinder, about half way down the bore...

Is this a 1.7 or a 1.9??
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Post by jeremy »

Its possible there are small cracks in the head which close up as soon as the head gets warm - so I suppose when cold - too small to allow water into the bores - but will allow gas into the cooling water and seal up as the engine warms.
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Jaba
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Post by Jaba »

  • Doc wrote:
they usually go in number cylinder, about half way down the bore...


Doc its a 1.7. Which cylinder did you mean they usually go in ?

Jeremy , To test your theory I will let it warm up with the rad cap off and see if the vapour quantity changes.

Bugger this will mean two engine changes in 2000 miles :evil: .
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Post by DavidRutherford »

Try this:

Begin with a cold engine, and remove and replace the pressure cap to ensure the system is equalised with atmospheric pressure.
Start and run the engine for 30 seconds, then stop it.
Now remove the pressure cap again. Was there a release of pressure?

If No, then I don't believe it's a head gasket.
If Yes, then it is combustion gas getting into the coolant somewhere, be that a gasket, a cracked head or a porus block.

Of the three possibilities, I'd least expect it to be the block, as if a block is going to go porus, it usually does so early on in its life.
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Jaba
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Post by Jaba »

Good test David. Spot on too. It pressurises almost instantly.
Funny that it still runs well though. Although this morning it only started on 3 cylinders initially. Hope its just the gasket.
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Post by AndersDK »

On a TD you remove the head complete with both manifolds still fitted. Otherwise you end up with endless aggro ... :roll:

Refitting is a revers ...

With head off its worth doing over the manifold mounting bolts, studs & nuts. Preferably replace studs with stainless (80mm) M8 bolts, then hacksaw off the heads and finish off with a thread cleaning.
Note that the nuts may be the odd special 10mm spanner size but still being an 8mm thread - to accomodate the very narrow space.
New genuine nuts are - nuts - from your dealer :wink:
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