Saab 9000 head gasket woes.
Discussion
I'm a bit stumped so asking the PH collective for opinions. The short story is that I rebuilt a spare cylinder head from a former car and fitted it to my current car which needed a new head gasket. It was all chemi-cleaned and the valves were lapped in.
I've had it running and revvng but it became 'lumpier' so i switched off. Compression readings before hand were quite low 6-8 bar etc. The previous head was at 12 bar. I put this down to the followers not having primed. Today I have 10, 9, 7 and 8 bar. All readings were on a cold engine, WOT.
My concern is that I have some coolant in the oil that wasn't there before I ran the engine up to temp.
Piston crowns are all clean and dry. At the front of the head/block is a single drilling for oil to reach the cylinder head. it would be rotten luck if coolant is reaching that gallery.
Can anybody think of an external crossover point where coolant can get into the oil? Failing that I'll have to remove the head again :-)
I've had it running and revvng but it became 'lumpier' so i switched off. Compression readings before hand were quite low 6-8 bar etc. The previous head was at 12 bar. I put this down to the followers not having primed. Today I have 10, 9, 7 and 8 bar. All readings were on a cold engine, WOT.
My concern is that I have some coolant in the oil that wasn't there before I ran the engine up to temp.
Piston crowns are all clean and dry. At the front of the head/block is a single drilling for oil to reach the cylinder head. it would be rotten luck if coolant is reaching that gallery.
Can anybody think of an external crossover point where coolant can get into the oil? Failing that I'll have to remove the head again :-)
^ Thanks. The oil was clean. I checked it when taking the new compression readings, before running the engine. I'm sure it became contaminated as the engine heated up. The engine note changed and it ran rougher.
I do suspect the head gasket. It could be leaking into the timing chest. I'll probably start to take it apart later.
I do suspect the head gasket. It could be leaking into the timing chest. I'll probably start to take it apart later.
Boosted LS1 said:
^ Thanks. The oil was clean. I checked it when taking the new compression readings, before running the engine. I'm sure it became contaminated as the engine heated up. The engine note changed and it ran rougher.
I do suspect the head gasket. It could be leaking into the timing chest. I'll probably start to take it apart later.
What a nightmare, I feel for you. I'm about to swap engines and am expecting anything, I could easily end up in the same situation as the one you are now inI do suspect the head gasket. It could be leaking into the timing chest. I'll probably start to take it apart later.
Good luck
That's the only thing I don't miss about my 9000 aero's, I became so good at removing heads that I could get one off in a couple of hours.
I changed a head one once and one cylinder had absolutely no compression according to the tester, took a while to find out what wad wrong, in the end it turned out that the hydraulic tappets were all remaining pumped up and one of the valves was not closing. I had to measure each gap and each tappet and then select the tappets to suit each valve, I put it back together and it ran fine.
Another one went through three head gaskets in quick succession, I eventually fixed it when I changed the head itself, the strange thing was the head was flat when fitted each time and the block was good too.
Good luck with the head off job today.
I changed a head one once and one cylinder had absolutely no compression according to the tester, took a while to find out what wad wrong, in the end it turned out that the hydraulic tappets were all remaining pumped up and one of the valves was not closing. I had to measure each gap and each tappet and then select the tappets to suit each valve, I put it back together and it ran fine.
Another one went through three head gaskets in quick succession, I eventually fixed it when I changed the head itself, the strange thing was the head was flat when fitted each time and the block was good too.
Good luck with the head off job today.
^ Thanks. Well it's all apart and I can't see anything amiss. The new gasket shows signs of compression everywhere and measures a similar thickness to the old gasket. The head seems flat enough measured with a straight edge and a torch. The bores are amazing. 200'000 miles and they're smooth with no wear ridge.
The only thing I did notice and this would be down to me when I assembled it. The timing cover is sitting slightly proud of the head. I can feel it with my nail. Whether that's tilted the head and allowed oil into the timing chest I'll probably never know. That said the gasket shows signs of compression. Hmm I think I'll dress it with a file.
The only thing I did notice and this would be down to me when I assembled it. The timing cover is sitting slightly proud of the head. I can feel it with my nail. Whether that's tilted the head and allowed oil into the timing chest I'll probably never know. That said the gasket shows signs of compression. Hmm I think I'll dress it with a file.
You work fast, is it possible there is a seal missing from somewhere, I don't know the engine hence I don't understand the timing cover fitment that you mention. I do know that your problems and staying power are pshycing me up for what I'm about to get started on but that's not going to solve your problem
Nightmare
Nightmare
The compression readings suggest there's a fairly major problem. The fact it affects all cylinders and the engine ran points away from the valve train. I wonder if the problem was simply that the head/block seal was blowing everywhere. I would have thought you'd hear that, and it would also be obvious in a leakdown test. If the problem persists, a leakdown test looking for the cause of those compression results would be my next step.
^^ No missing seals. If only it were as simple :-)
Hi Peter,
The head gasket's clean, no blowby on it. As said, followers were replaced and certainly a bit tappety when I started it. That reminded me of my RV8 thodes lifters ;-) The compression has risen but I didn't really have the chance to run the engine for very long.
Looking at the head design, there are only two oil routes down to the sump. First drain back is via the timing chest. The other drain back is at the other end of the block. Both drain backs have a water source about an inch away. I suspect it's the timing chest where my problem lies but I'd like to be more certain.
Hi Peter,
The head gasket's clean, no blowby on it. As said, followers were replaced and certainly a bit tappety when I started it. That reminded me of my RV8 thodes lifters ;-) The compression has risen but I didn't really have the chance to run the engine for very long.
Looking at the head design, there are only two oil routes down to the sump. First drain back is via the timing chest. The other drain back is at the other end of the block. Both drain backs have a water source about an inch away. I suspect it's the timing chest where my problem lies but I'd like to be more certain.
I assume the head and timing chest are in parts now so all you can really do at this stage is look for evidence of a failed seal and be very careful putting it back together. A dry pressure test on the cooling system can sometimes let you locate leaks by sound, at least to get a rough location.
I suspect the water leak is going to be the hardest to fix but the low CR and lumpy running worries me more.
Assuming the bottom end was and is sound, it would have to be either a cam timing fault or valves not opening and closing properly. Did you collapse the lifters and check the preload while it was going back together?
I suspect the water leak is going to be the hardest to fix but the low CR and lumpy running worries me more.
Assuming the bottom end was and is sound, it would have to be either a cam timing fault or valves not opening and closing properly. Did you collapse the lifters and check the preload while it was going back together?
I’m feeling your pain also.
Rebuilt my first ever engine on a mk3 mr2, mechanic mate helped me, spent ages checking it all as I was learning then had to get back into car without a ramp etc as did on drive, then new clutch etc.
Then stick all over stuff on. Finally done. Before starting I cleared up the garage only to find a brand new thrust bearing ! b
ks so gearbox came back out and fitted thrust bearing. Then came start up day. 2 hours later still won’t start. Pressure test etc showing issues.
Head back off and away for flatting and valves all checked etc. Bloke did work and said nothing wrong with that you’ve wasted your money. Turned out to be a faulty gasket !
All bolted back on started and running. That was 1000 miles ago. Guess what I did last week ! Took gearbox out and replaced it as bearings inside gone !
So I really really feel your pain, keep at it. Also what make is your gasket I can’t recall what mine was but the head guy said I’ve had a few issues with them and gave (sold) me a German make.
Rebuilt my first ever engine on a mk3 mr2, mechanic mate helped me, spent ages checking it all as I was learning then had to get back into car without a ramp etc as did on drive, then new clutch etc.
Then stick all over stuff on. Finally done. Before starting I cleared up the garage only to find a brand new thrust bearing ! b
ks so gearbox came back out and fitted thrust bearing. Then came start up day. 2 hours later still won’t start. Pressure test etc showing issues.Head back off and away for flatting and valves all checked etc. Bloke did work and said nothing wrong with that you’ve wasted your money. Turned out to be a faulty gasket !
All bolted back on started and running. That was 1000 miles ago. Guess what I did last week ! Took gearbox out and replaced it as bearings inside gone !
So I really really feel your pain, keep at it. Also what make is your gasket I can’t recall what mine was but the head guy said I’ve had a few issues with them and gave (sold) me a German make.
Thanks gents. I'm going to realign the timing cover later just in case it was the source of my coolant issue with the head gasket. I'd have preferred to have found a more obvious fault.
The refurbished head did have some different lifters in it. They were seized so I fitted mine in the assumption that since the rest of the parts are identical the lifters should take up the slack. That said, the original lifters have a taller nipple and the overall height is slightly greater. If my current lifters aren't opening the valves far enough then this may be a cause for the lowered c/r readings.
So, today, I'll unseize 16 lifters and install them and I'll realign the timing chest :-)
ETA. Definately a different lifter. Taller plunger, smaller oil chamber and the oil supply hole is in a higher position. Oil supply holes in the head are the same for both heads that I've examined.
The refurbished head did have some different lifters in it. They were seized so I fitted mine in the assumption that since the rest of the parts are identical the lifters should take up the slack. That said, the original lifters have a taller nipple and the overall height is slightly greater. If my current lifters aren't opening the valves far enough then this may be a cause for the lowered c/r readings.
So, today, I'll unseize 16 lifters and install them and I'll realign the timing chest :-)
ETA. Definately a different lifter. Taller plunger, smaller oil chamber and the oil supply hole is in a higher position. Oil supply holes in the head are the same for both heads that I've examined.
Edited by Boosted LS1 on Sunday 13th May 10:18
Another thought - It would be worth checking and checking again the timing........ rotate the engine a turn or two by hand tool with the plugs out. Ensure the marks on the camshafts match to the timing marks on the head and that the mark on the crank pulley is also aligned.
It's quite easy to get them one tooth out.
It's quite easy to get them one tooth out.
^ Thanks Richard.
I set it all at tdc number one, marks aligned when I took it apart but I have rechecked this and all's well. What's frustrating is that I haven't found an obvious fault for the coolant issue. Nearest issue is the timing cover misalignment. BTW all my parts etc are short block parts/engines. The refurbed head is date marked 1994.
Fingers crossed it all works when I put it back together in the next couple of days. :-)
You're on UK Saabs, small world :-)
I set it all at tdc number one, marks aligned when I took it apart but I have rechecked this and all's well. What's frustrating is that I haven't found an obvious fault for the coolant issue. Nearest issue is the timing cover misalignment. BTW all my parts etc are short block parts/engines. The refurbed head is date marked 1994.
Fingers crossed it all works when I put it back together in the next couple of days. :-)
You're on UK Saabs, small world :-)
I can give an update on this now I've sorted it. Despite lapping in the best valves I could find into the refurbished head the exhaust valves on the middle 2 cylinders were leaking. This was the cause of the low compression.
I couldn't find the cause of the coolant pressure even though I had swopped heads and fitted new gaskets.
In the end I rebuilt the original head, lapped in the valves, fitted new stem seals and then I fitted this head. I got 12 bar on the end cylinders and 11 bar on the middle 2 where the pistons had been sitting at the bottom of the bores. I suspect the lower reading could be because the bores were dry. The car runs well with no hint of coolant pressure. The top hose may be hot but it's soft and easily compressed by hand.
I had also, flushed the radiator, checked the thermostat and replaced the water pump to make sure I had coolant flow.
All seems good now so I'll get onto the humming wheel bearing next :-)
I couldn't find the cause of the coolant pressure even though I had swopped heads and fitted new gaskets.
In the end I rebuilt the original head, lapped in the valves, fitted new stem seals and then I fitted this head. I got 12 bar on the end cylinders and 11 bar on the middle 2 where the pistons had been sitting at the bottom of the bores. I suspect the lower reading could be because the bores were dry. The car runs well with no hint of coolant pressure. The top hose may be hot but it's soft and easily compressed by hand.
I had also, flushed the radiator, checked the thermostat and replaced the water pump to make sure I had coolant flow.
All seems good now so I'll get onto the humming wheel bearing next :-)
Boosted LS1 said:
I can give an update on this now I've sorted it. Despite lapping in the best valves I could find into the refurbished head the exhaust valves on the middle 2 cylinders were leaking. This was the cause of the low compression.
I couldn't find the cause of the coolant pressure even though I had swopped heads and fitted new gaskets.
In the end I rebuilt the original head, lapped in the valves, fitted new stem seals and then I fitted this head. I got 12 bar on the end cylinders and 11 bar on the middle 2 where the pistons had been sitting at the bottom of the bores. I suspect the lower reading could be because the bores were dry. The car runs well with no hint of coolant pressure. The top hose may be hot but it's soft and easily compressed by hand.
I had also, flushed the radiator, checked the thermostat and replaced the water pump to make sure I had coolant flow.
All seems good now so I'll get onto the humming wheel bearing next :-)
I couldn't find the cause of the coolant pressure even though I had swopped heads and fitted new gaskets.
In the end I rebuilt the original head, lapped in the valves, fitted new stem seals and then I fitted this head. I got 12 bar on the end cylinders and 11 bar on the middle 2 where the pistons had been sitting at the bottom of the bores. I suspect the lower reading could be because the bores were dry. The car runs well with no hint of coolant pressure. The top hose may be hot but it's soft and easily compressed by hand.
I had also, flushed the radiator, checked the thermostat and replaced the water pump to make sure I had coolant flow.
All seems good now so I'll get onto the humming wheel bearing next :-)
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