Diagnosing a valve seal problem
#1
Diagnosing a valve seal problem
After ruling out other parts of the car (Turbo - went for service, rings - got a compression test done, all at 120psi) I am thinking that I have worn valve stems/seals in my heads which the cause for the smoke beign produced from the back of the car.
The problem is been happening for the last year or so but has become noticably worse in the last few months with smoke appearing from pulling out from junctions not just from conditions under boost.
It there any way of checking to be sure that this is my problem before I pay to get the engine taken out and the heads replaced? Its gonna get expensive if I do....!
Nezz.
The problem is been happening for the last year or so but has become noticably worse in the last few months with smoke appearing from pulling out from junctions not just from conditions under boost.
It there any way of checking to be sure that this is my problem before I pay to get the engine taken out and the heads replaced? Its gonna get expensive if I do....!
Nezz.
#3
Scooby Regular
Join Date: Nov 2004
Location: In a 405 BHP/360 ft/lb P1 with SN superstar Sonic dog at my side!
Posts: 1,959
Likes: 0
Received 0 Likes
on
0 Posts
worn valve seals wont cause a compression loss. normally when these go you get smoke for a minute or so after start up (talking bikes and cars here with verticalish cylinders, not sure if it would be the same with horizontal scoob pots) but then it goes.
we run some race bikes without any seals deliberately and you still only smoke on start up, so i dont think your smoke is down to this.
worn valve guides wont cause it directly either, but this will give your valve seat and valve 45deg sealing angle a harder time, making them recede/wear quicker. then obviously you may get compression losses and/or a bit of smoke.
if your valve to guide clearance is like a **** in a bucket, you may get a bit of smoke but yours does sound a bit more than that.
i think you are gonna have to take the engine out and whip the heads off to confirm though unfortunately
we run some race bikes without any seals deliberately and you still only smoke on start up, so i dont think your smoke is down to this.
worn valve guides wont cause it directly either, but this will give your valve seat and valve 45deg sealing angle a harder time, making them recede/wear quicker. then obviously you may get compression losses and/or a bit of smoke.
if your valve to guide clearance is like a **** in a bucket, you may get a bit of smoke but yours does sound a bit more than that.
i think you are gonna have to take the engine out and whip the heads off to confirm though unfortunately
#5
Scooby Regular
Join Date: Jun 2003
Location: 348/330 on a 90*entry TD05 16G
Posts: 547
Likes: 0
Received 0 Likes
on
0 Posts
Could just be a build up of oil in the intercooler/inlet manifold from the breathers that come from the crankcase and rocker covers.
Probably not this , but worth a look before you go stripping the engine.
Probably not this , but worth a look before you go stripping the engine.
#6
Scooby Regular
Join Date: Nov 2004
Location: In a 405 BHP/360 ft/lb P1 with SN superstar Sonic dog at my side!
Posts: 1,959
Likes: 0
Received 0 Likes
on
0 Posts
yeah good point andy. whip the IC off, i should think it would be dripping in the neck to cause that much smoke.
how many miles has the motor done? had a hard life? lots of short journeys etc.?
how many miles has the motor done? had a hard life? lots of short journeys etc.?
#7
Originally Posted by p1mark
worn valve seals wont cause a compression loss. normally when these go you get smoke for a minute or so after start up (talking bikes and cars here with verticalish cylinders, not sure if it would be the same with horizontal scoob pots) but then it goes.
we run some race bikes without any seals deliberately and you still only smoke on start up, so i dont think your smoke is down to this.
worn valve guides wont cause it directly either, but this will give your valve seat and valve 45deg sealing angle a harder time, making them recede/wear quicker. then obviously you may get compression losses and/or a bit of smoke.
if your valve to guide clearance is like a **** in a bucket, you may get a bit of smoke but yours does sound a bit more than that.
i think you are gonna have to take the engine out and whip the heads off to confirm though unfortunately
we run some race bikes without any seals deliberately and you still only smoke on start up, so i dont think your smoke is down to this.
worn valve guides wont cause it directly either, but this will give your valve seat and valve 45deg sealing angle a harder time, making them recede/wear quicker. then obviously you may get compression losses and/or a bit of smoke.
if your valve to guide clearance is like a **** in a bucket, you may get a bit of smoke but yours does sound a bit more than that.
i think you are gonna have to take the engine out and whip the heads off to confirm though unfortunately
Very often, it is possible to change the stem seals (and springs) without removing the head, but I think accessibility would rule this out on a Subaru.
Trending Topics
#8
IC is front mount, all breather lines connected to catch tank and none back into the inlet pipe. Motor is a MY00 UK turbo with 60K on the clock.
Standard block and heads, MD304 turbo, gruppe-s headers, HKS exhuast parts, HKS air filter blah blah.
If sitting at the lights or cruising for a little then blast it, lots of smoke.
Coming off from crusing on the motorway then floor it down a dual carriageway gives off less smoke but still a fair bit - mostly as the turbo spins up and at top revs it gives out more but increase flow thru the engine woudl do this to.
Once the car has had a bit of boost thru it then it seems to be a lot better with minmal to no smoke.
Turbo has been sent back to TD for full repair and is still 3 months under warranty, as said above compression check came out at 120psi all round. Has has a fairly hard life being tuned to 300ish HP for the last 4/5 years. Wouldnt say a lot of short journeys really just normal road useage and a few track/airfeild days.
Tempted to try another turbo just to make sure its not that first!!
Standard block and heads, MD304 turbo, gruppe-s headers, HKS exhuast parts, HKS air filter blah blah.
If sitting at the lights or cruising for a little then blast it, lots of smoke.
Coming off from crusing on the motorway then floor it down a dual carriageway gives off less smoke but still a fair bit - mostly as the turbo spins up and at top revs it gives out more but increase flow thru the engine woudl do this to.
Once the car has had a bit of boost thru it then it seems to be a lot better with minmal to no smoke.
Turbo has been sent back to TD for full repair and is still 3 months under warranty, as said above compression check came out at 120psi all round. Has has a fairly hard life being tuned to 300ish HP for the last 4/5 years. Wouldnt say a lot of short journeys really just normal road useage and a few track/airfeild days.
Tempted to try another turbo just to make sure its not that first!!
#9
Former Sponsor
Join Date: Jul 2005
Location: Wellingborough, Northamptonshire
Posts: 2,859
Likes: 0
Received 0 Likes
on
0 Posts
it doesn't sound valve related to me. Valve problems don't usually present such consistent results accross all cylinders. Depending on how much you want to try and diagnose yourself, you could try and remove the inlet manifold and turn the engine over by hand with some fluid in the inlet ports (brake cleaner for instance) and see if you get air hissing past the valves, obviously harder to test the exhaust side like that.
A leakdown test may also be useful, and you can also try the leakdown and compression tests with some oil squirted into the bores before hand, which will help seal the rings and show up a ring seal issue (ie if oil makes it much better then valves probably not the problem).
Paul
A leakdown test may also be useful, and you can also try the leakdown and compression tests with some oil squirted into the bores before hand, which will help seal the rings and show up a ring seal issue (ie if oil makes it much better then valves probably not the problem).
Paul
#10
For my money, the turbo seals have gone. take the car to the manufacturer / supplier ( Turbo Dynamics was it ?? ) for a diagnosis, or else others like Zen Performance, Xtreme Scoobies, APi, Scoobyclinic, Lateral, ASPerformance etc.
For oil smoke out of the exhaust it needs to get IN to the exhaust stream, so that's either in the combustion chamber/ cylinder, or else afterwards.
Oil via valve stems on these flat engines is not too likely, not in significant quantities despite high vacuum in the cylinder - not that much oil about there and at no pressure. Ditto oil via rings unless rings really shot - no pressurised liquid oil feed at piston ring surface ( maybe more for engines with under piston crown oil squirters )
So probably from turbo via the turbo seals / bearings.
My puffs of smoke came on lift off from hard boost on OEM D04 turbo, was due to to worn turbo.
For oil smoke out of the exhaust it needs to get IN to the exhaust stream, so that's either in the combustion chamber/ cylinder, or else afterwards.
Oil via valve stems on these flat engines is not too likely, not in significant quantities despite high vacuum in the cylinder - not that much oil about there and at no pressure. Ditto oil via rings unless rings really shot - no pressurised liquid oil feed at piston ring surface ( maybe more for engines with under piston crown oil squirters )
So probably from turbo via the turbo seals / bearings.
My puffs of smoke came on lift off from hard boost on OEM D04 turbo, was due to to worn turbo.
#12
Everyone's assuming it's oil but you haven't mentioned what colour the smoke is. Oil = blue; fuel = black; water = white
Also, condition and consistency of the plugs, i.e. colour, wet/dry, oily, may indicate where to look.
Gerry
Also, condition and consistency of the plugs, i.e. colour, wet/dry, oily, may indicate where to look.
Gerry
#14
Former Sponsor
Join Date: Jul 2005
Location: Wellingborough, Northamptonshire
Posts: 2,859
Likes: 0
Received 0 Likes
on
0 Posts
hmmm, not good. Blue smoke is deffo something that needs to be investigated. I may be massive overfuelling which causes oil in the cylinder to be diluted and ingested past the piston rings. But blue smoke is most like to be linked with some positive leak, like a piston or valve stem seal problem.
Paul
Paul
#15
Former Sponsor
iTrader: (4)
Join Date: Jul 2003
Location: @Junc 12, M40 Warwicksh; 01926 614522 CV33 9PL -Use 9GX for Satnav. South Mids Alcatek ECu dealer
Posts: 6,377
Likes: 0
Received 3 Likes
on
3 Posts
Originally Posted by Zen Performance
hmmm, not good. Blue smoke is deffo something that needs to be investigated. I may be massive overfuelling which causes oil in the cylinder to be diluted and ingested past the piston rings. But blue smoke is most like to be linked with some positive leak, like a piston or valve stem seal problem.
Paul
Paul
David APi Engines / APi Impreza
www.apiengines.com
#16
David,
Turbo went back on today but havent had chance to try to replicate the problem again yet.
You may be getting a phone call from me in the week to discuss how to progress with this.
Neil.
Turbo went back on today but havent had chance to try to replicate the problem again yet.
You may be getting a phone call from me in the week to discuss how to progress with this.
Neil.
Thread
Thread Starter
Forum
Replies
Last Post
Mattybr5@MB Developments
Full Cars Breaking For Spares
12
18 November 2015 07:03 AM
shorty87
Wheels And Tyres For Sale
0
29 September 2015 02:18 PM