Blue smoke on start-up after fitting of recon TD cyl head

andycadabra · Post by **andycadabra** » Fri Mar 05, 2010 11:48 am

I bought a reconditioned (and guaranteed) cylinder head on eBay for £175, which was supposed to have had all seals replaced, but a bit worried about the amount of blue smoke on start-up, and that this might be down to the fact that the seals weren't replaced?
I've written to the seller, and have pasted my message and his reply below.

Hi - thanks for your message. I have had the head fitted now, and I'm just a bit concerned about the amount of blue smoke coming out of the exhaust on start-up. The fact that it occurs only on start-up suggests that its probably not down to piston ring/cylinder wear, but oil leakage into the cylinders past the valve stem seals?. Surely this shouldn't happen if the seals have been replaced?. If it's any help I could post a video showing their head, and then the start-up smoke, on youTube.
Cheers
A

Hi Andy, as you can imagine an old engine thats been running fine all of a sudden starts to smoke when any engine work has been carried out, could be a number of things, especially when compression is altered, EG diesel pump timing, injectors, piston rings(oil ring).we have never had any problems with valve stem seals which are new.I have in past had early peugeots smoke on start up till its carboned up on combustion side.
Cheers
B

From what I've understood, blue smoke signifies burning oil, and not a fuel related issue, and the fact that it no longer smokes once it's been running means it's not piston ring wear. Does anyone have any thoughts?. Should I pursue it or learn to live with it?.
Would not changing the seals have saved them much time/expense anyway?

Aerodynamica · Post by **Aerodynamica** » Fri Mar 05, 2010 12:13 pm

Is it a turbo? It might be that the turbo is leaking oil though admittedly it would more likely burn oil under revving not just on start up.

Just a thought really.

Brian · Post by **Brian** » Fri Mar 05, 2010 3:10 pm

As far as I am aware, the diesel engine is not fitted with valve stem seals, only the petrol engine.

Unless anyone knows different...

andycadabra · Post by **andycadabra** » Fri Mar 05, 2010 3:34 pm

Aerodynamica - Yes it is a turbo, I must confess that I hadn't considered that turbos could leak oil.
Brian - that's interesting - surely there must be some seals to stop oil in the top of the engine leaking down into the cylinders via the valve stems, while the car's been standing a while?

Post by **mat_fenwick** » Fri Mar 05, 2010 3:37 pm

I've heard the same, but whenever I have bought HG sets for the XUD engine they contained valve stem seals (but never fitted them personally). The semi reconditioned head I bought last year had them fitted, or so I was told.

Brian · Post by **Brian** » Fri Mar 05, 2010 5:28 pm

Well I have removed heads from at lease 6 diesel engines in the past and none have had them fitted.

In fact the Haynes BOL does not show or mention them in the diesel book.

Thinking about it, oil ingress via the valve stem guide gap occurs on petrol engines mainly on the overrun, when the induction tract in under negative pressure.

The diesel engine has very little negative pressure on the overrun, as there is no restriction on the intake, it's open ended, no butterfly.

DavidRutherford · Post by **DavidRutherford** » Sat Mar 06, 2010 11:41 am

Early XUD engines had no stem seals. This was true up to about 1988ish, at which point a modified guide was fitted with a stem seal. I don't like the stem seals, as it does mean the guide is not lubricated, and I've had some remarkable guide wear on a 1.9TD engine. I've since had this head fitted with new guides, and opted to have the non-stem-seal guides fitted. The amount of oil it uses is utterly insignificant in comparison to knowing that my valve guides aren't being worn out.

Blue smoke on start-up does seem to indicate that some oil is getting in somewhere, but I doubt it's the guides. That said, try starting the engine a couple of times with no intercooler on it, which means there is absolutely no vacuum in the inlet manifold whatsoever, and see if it does the same. If it does, then you have some evidence that it is getting in somewhere else.

Also.. does it happen if you leave the car off for just 5 minutes and then re-start it? If not, roughly how long does it have to be left for it to smoke blue on startup?

tom · Post by **tom** » Sat Mar 06, 2010 11:44 pm

Blue smoke or steam? Why was the head changed? Are the injectors the same ones that came out? Is the performance up to scratch?

kiwi · Post by **kiwi** » Sun Mar 07, 2010 9:48 am

tom wrote:Why was the head changed?

This may help you Tom

http://www.bxclub.co.uk/forum/viewtopic ... highlight=

andycadabra · Post by **andycadabra** » Sun Mar 07, 2010 6:57 pm

Thanks for all the helpful replies.
I checked the Haynes manual for the diesel engine and it did mention stem seals, at least in the faultfinding section. Although my car is a 92, I've no idea of the year of the car the reconditioned head came from so it may have stem seals, or not.
I've done some tests over the weekend. If left to tick over at 9k rpm after starting the smoke is visible, but negligible. Increasing the revs to 15k RPM is not something I'd want to do while a pedestrian was passing. After it's been running 10 minutes or so, it needs to be revved to over 23k RPM to generate the same level of smoke. Restarting after 15 minutes didn't produce much in the way of smoke, but restarting after 3 hours did, although I don't think as much as starting it from cold tomorrow morning will.
Tom - blue smoke, not steam I'd say. The last head had a crack down the middle, leading to too much pressure in the cooling system. It has the same injectors as before.
I'm not sure the timing is spot on since there's a touch of unevenness in the engine tickover every few seconds - would this be down to timing?.

kiwi · Post by **kiwi** » Sun Mar 07, 2010 9:07 pm

andycadabra wrote:I've done some tests over the weekend. If left to tick over at 9k rpm after starting the smoke is visible, but negligible. Increasing the revs to 15k RPM is not something I'd want to do while a pedestrian was passing. After it's been running 10 minutes or so, it needs to be revved to over 23k RPM to generate the same level of smoke. Restarting after 15 minutes didn't produce much in the way of smoke, but restarting after 3 hours did, although I don't think as much as starting it from cold tomorrow morning will.

As a thought what is the weather like when you conduct theses tests? ie the atmospheric temperature/humidity etc?

sdelasal · Post by **sdelasal** » Sun Mar 07, 2010 10:38 pm

How long have you run the engine for?

I recon'd the head on a vw diesel some time back and the smoke on startup was embarrasing ...i ran it for ~20min - still smoking ...so, thinking I had nothing to loose, I took it for a blast down the road and within 1/2 mile the smoke cleared and has been fine ever since. In my case, it was excess oil that i had slopped around whilst storing, honing bores and generally re-assemble.

Steve

andycadabra · Post by **andycadabra** » Thu Mar 11, 2010 2:56 pm

He is a video of the situation for everyone's amusement.
I was revving it at 15,000 to 20,000, and finally leaving it at tickover.

Atmospheric conditions were 61% humidity, 1025MB of pressure, Kiwi..

Steve - it was done 3 weeks ago,and has been driven about 160 miles since then.

kiwi · Post by **kiwi** » Thu Mar 11, 2010 6:24 pm

andycadabra wrote:
Atmospheric conditions were 61% humidity, 1025MB of pressure, Kiwi..

^^^
Should I really have asked

And the temperature was?

Are you sure you fitted the head properly?

andycadabra · Post by **andycadabra** » Thu Mar 11, 2010 6:44 pm

About 8-9C, and I didn't fit it - the garage did (the one I would trust to do a decent job).
would you say it was acceptable?