SweetBadger 94 Posted May 25, 2008 This follows on from an earlier post where I discovered that cylinders 2 & 3 in my MI were down to 160 - 165 psi... I put this down to a head gasket problem or some valves not sealing properly as the liners and rings were replaced about 18k ago and cylinders 1 & 4 were showing 210psi... I've got me a new head but upon stripping the engine to take the old head off I found this in the inlet ports... It's quite tacky oily residue, is this just normal oil vapour being sucked into the breather system and condensing or does it look excessive? In which case it might suggest that the rings are buggered and I'm getting excessive blowby ... There's no wear lip on the bores and they look in good nick... there's some very light vertical marks but nothing that you can feel with your finger. When it was running it didn't smoke or use much oil, and there didn't seem to be any excessive vapour coming out of the oil filler when I removed it to have a check. tried to take a piccy of one of the bores but it didn't come out too well - see below Don't really want to bolt the new head on and waste yet another set of head bolts and a gasket but I guess the only thing to do now is bolt it all together and see. Any suggestions? Share this post Link to post Share on other sites
DamirGTI 342 Posted May 25, 2008 Could be worn valve guides check if there's any carbon deposits at the back of the inlet valve heads .. Rgs ! Damir Share this post Link to post Share on other sites
James_m 0 Posted May 25, 2008 Hmm, i would'nt risk putting that back together. If the oil was coming through the breather system, all 4 cyls would see equal oil, but from the pic it would appear your 2 weak cyls's are seeing much more, which would indicate its some how coming from the bottom end? ive never seen oil like that on the ports normally, so something must be amss id say. Yet oil usage is low..... Very odd, im interested to see the outcome on this one. Share this post Link to post Share on other sites
SweetBadger 94 Posted May 25, 2008 Hmm, i would'nt risk putting that back together.If the oil was coming through the breather system, all 4 cyls would see equal oil, but from the pic it would appear your 2 weak cyls's are seeing much more, which would indicate its some how coming from the bottom end? ive never seen oil like that on the ports normally, so something must be amss id say. Yet oil usage is low..... Very odd, im interested to see the outcome on this one. I don't think it's coming from the bottom end as it's carbonised dirty tacky oil and the stuff in the sump is quite fresh... When the head came off there was no sign of oil in the combustion chamber and the oily residue is inside the inlet manifold too which points to oil vapour. Plus for the oil to get back into the inlet tract the inlet valves would have to be leaking quite badly. Guess it could have been drawn through the valve guides/stems but that would have caused the engine to smoke and it's only done about 6 k since I changed the head and stemseals after my first head got some bent inlets after some gravel got in the cambelt... Ahhh, what to do! Can't see any reason why the rings would suddenly have gone on those 2 cylinders. Might put the head on using the old HG and bolts and just do a cold compression test to see if the new head solves the problem then if it's ok I can fit the new HG and bolts. Sound feasable? Share this post Link to post Share on other sites
DamirGTI 342 Posted May 26, 2008 Guess it could have been drawn through the valve guides/stems but that would have caused the engine to smoke and it's only done about 6 k since I changed the head and stemseals after my first head got some bent inlets after some gravel got in the cambelt... Not necessarily smoking usually starts in the late stadium of the malfunction ... oil can escape (can be sucked ..) past worn valve guides or worn (incorrectly fitted) steam seals under presence of high vacuum inside the inlet tract , and you'll notice that by unusual amount of oil inside the inlet manifold/ports and particularly at the back of the valve heads - remove and inspect all the inlet valves , if you see carbon deposits on the valves that will be burnt oil which came past the valve guides/steam seals down on to the valves .. Rgs ! Damir Share this post Link to post Share on other sites
SweetBadger 94 Posted May 26, 2008 (edited) Not necessarily smoking usually starts in the late stadium of the malfunction ... oil can escape (can be sucked ..) past worn valve guides or worn (incorrectly fitted) steam seals under presence of high vacuum inside the inlet tract , and you'll notice that by unusual amount of oil inside the inlet manifold/ports and particularly at the back of the valve heads - remove and inspect all the inlet valves , if you see carbon deposits on the valves that will be burnt oil which came past the valve guides/steam seals down on to the valves .. Rgs ! Damir Hmm I think we may be onto something here! Every inlet valve looked like this: The residue is the same sticky crap found in the inlet port and tract. However even if the stem seals/guides were going causing the residue how would this cause the low compression? The valve seats looked fine and it definetly wasn't the HG I can't help but think that the oil came from the breather system. I'm beginning to think it may be worth just whipping cyls 2& 3 out while the head's off, getting the liners honed and fitting new rings for peace of mind... Edited May 26, 2008 by SweetBadger Share this post Link to post Share on other sites
DamirGTI 342 Posted May 26, 2008 Those valves seems fine (apart from first one from the right which has a little bit thicker carbon ring .. although it's not much if the guides/seals are worn you'll expect to see thicker layer of deposits ..) , must be something else then Just one thing which i've discover recently - when i remove the wire mesh out from the oil filler cap afterwards i always find quite a big amount of oil around throttle butterfly and inside the first inlet pipe (TB to AFM pipe ..) , and when i refit the wire mesh back this oil residue disappears from the inlet tract Damir Share this post Link to post Share on other sites
SweetBadger 94 Posted May 26, 2008 (edited) Those valves seems fine (apart from first one from the right which has a little bit thicker carbon ring .. although it's not much if the guides/seals are worn you'll expect to see thicker layer of deposits ..) , must be something elsethen Just one thing which i've discover recently - when i remove the wire mesh out from the oil filler cap afterwards i always find quite a big amount of oil around throttle butterfly and inside the first inlet pipe (TB to AFM pipe ..) , and when i refit the wire mesh back this oil residue disappears from the inlet tract Damir The one with the thicker carbon ring came out of cyl 1 (one of the good ones) and the others came out of cyl 3 so I can't put the oil or compression issues down to guides or stem seals... Are there any tell tale signs that a valve has not been sealing properly? The valve seats all looked ok - none of them had any pitting or burn marks, which points to the rings again Edited May 26, 2008 by SweetBadger Share this post Link to post Share on other sites
DamirGTI 342 Posted May 26, 2008 The one with the thicker carbon ring came out of cyl 1 (one of the good ones) and the others came out of cyl 3 so I can't put the oil or compression issues down to guides or stem seals... Are there any tell tale signs that a valve has not been sealing properly? The valve seats all looked ok - none of them had any pitting or burn marks, which points to the rings again Well for testing valve sealing you can try this : throughly clean the seat surface on the valves and also on the head , fit the valves (two by two) back inside in their port positions , angle the head a bit and press the valves on their heads tightly with your fingers , hold them like this and pour some liquid inside the inlet ports (in the ones where you've fitted the valves , you can use plain water , or petrol , paraffin etc ..) top up the inlet port with fluid and then keep on holding the valves pressed tight and observe if there will be any leaks past the valve heads into the chambers (while holding the valves tight rotate them a little bit on to the left/right..) - there should not be any leaks/droops from the ports past the valves into the chambers , not even a little bit ... Also you can try grinding the valves , preform just a short test lapping with fine grade paste , then clean throughly the valve seat (on the valves and on the head..) and examine the valve seat - you'll need to see nice unbroken gray ring on entire seat surface as you turn him with your hands , if not , if the gray ring isn't continuous on entire area of the seat (with broken areas , or with spots ..) then i will not seal completely .. try one more time the "liquid" test above when you test lap the valves , clean them throughly from grinding paste fit them back and again test for possible leaking .. Rgs ! Damir Share this post Link to post Share on other sites
SweetBadger 94 Posted July 6, 2008 After a frustrating few weeks I think I know what was causing the problems... The valves were sealing fine so the low compression was down to the rings, considering I built it with new liners and rings 20k ago there had to be a reason for this. When taking the head off for a second time it was pretty obvious that it was overfueling on the cylinders 2 & 3, so the low compression was down to bore wash The oil in the ports must have been caused by excessive blowby and I think the reason that there was more in cylinders 2 & 3 was down to the excessive fuel cooling and condensing the oil vapour before it had chance to get to the combustion chamber... Anyway took the sump off, whipped out the liners and had them honed, new rings and compression is back to 200 psi across the board. Also happy to report that after 4 trackdays not holding back on any corners the big ends were in really good nic, so in my case using a Gti6 sump plus spacer plate and a petert oil pump extension has been sucessful in taming surge problems. Share this post Link to post Share on other sites
James_m 0 Posted July 6, 2008 Good result, why was if overfuelling only on 2 and 3 though out of interest? Another quick question, how much oil are you using on track and what does that equate to on the dipstick? Im running around 6.5 litres which works out at just over half of the dipstick iirc and it still surges quite badly on the road Share this post Link to post Share on other sites
SweetBadger 94 Posted July 6, 2008 Must have been injectors sticking open as I'm running standard management so the injectors fire in batch. I've sent them off to be cleaned and tested, should really book it in for a rolling road tune too but prices per hour down south seem a bit excessive to me, and all you can do on standard management is tweak the AFM or play witht he fuel pressure. I always top the oil up to just above the top mark on the dipstick when I take it on track think that equates to approx 6.5 - 6.75 litres. I can't claim that I don't suffer oil surge as I'm still going off the crappy pug guess o meter, but judging by the big end shells the engine has never been at the point where there's been a total lack of oil pressure... Getting a propper mechanical guage is on the long list of outstanding things to do. Share this post Link to post Share on other sites
