Cylinder Heads
Discussion
Evening all,
I posted a couple of weeks ago after my S3 had been partial to a bit of overheating, resulting in me catching a lift home with Mr AA. I'm now at the stage of filling the garage with engine parts and trying to find out what's happened and what I'm to do next.
A couple of thing I've come across so far I thought I'd just throw out here to see if anybody has had similar thoughts or experiences....
First up, the only reason I can think its overheated is that all the coolant had removed itself from the expansion tank. Before the incident I'd noticed that often, upon pulling up after a drive, the cooling system would burble and slowly trickle water down the overflow pipe in the front wheelarch which, to me, would point to the expansion tank being too small for the needs of the engine?? Surely the coolant should flow into the tank when hot, be stored there as long as required, then return to the swirl pot when the engine cools down again. For reference the cap is pressurised on the expansion, non-pressurised on the swirl (worms....can...??!!)
I'd never let the coolant get low, but the morning of the incident I had been sat in some traffic going into manchester, so wonder if the coolant had dripped out during this time and I just hadn't realised until it was too late? Anyway, question is - would a larger expansion tank help here??
Next up, I've got the heads off the car (one cracked...) and noticed something unusual about the head gaskets. Although the coolant galleries are dotted all over the head and the engine block, the gasket doesn't appear to follow the same pattern and actually blocks some of the galleries off (or restricts them severely):
Block:
With gasket...
You can see how the gasket blocks off many of the coolant holes. Surely this must affect the coolant flow around the head, but is this intentional/helpful/a complete mystery?? I've seen a couple of other photos (think there is one on deadpineapple) that show a similar gasket too.
Finally for now, I've just this evening taken delivery of a pair of used heads from a chap on the 'bay who deals with breaking Sierras, seing as one of mine became cracked due to the overheat. I asked him twice if they were 2.9 12v heads and he confirmed they were. However I've just been having a look and I've noticed that there are a couple of small differences, the main one of which is the seating of the rocker shafts being slightly different. On my original head, the shaft has 'feet' of a square-ish shape that mate with the head perfectly. The new heads I've just received have a different shape that doesn't match the rocker feet. However the rocker shaft will bolt down onto the new head ok and sit, from what I can see, in the same position against the valve stem. I'm just trying to weigh up if there would be any risk using the existing rockers on the new head. There are a couple of cast-markings on the heads and I can clearly make out a '90' on mine, and an '87' on the new ones - can just be seen in the pics. Does anybody know if these are date markings? (thus I'm trying to fit older heads to my engine). I've got to be honest as well, I'm a little disappointed with the state of the heads this chap has sent - they're pretty sludgy and have a few snapped studs stuck in the exhaust manifold bolt holes. Hey-ho.....
My original heads -
And the used ones I've just purchased -
Any thoughts appreciated!
I posted a couple of weeks ago after my S3 had been partial to a bit of overheating, resulting in me catching a lift home with Mr AA. I'm now at the stage of filling the garage with engine parts and trying to find out what's happened and what I'm to do next.
A couple of thing I've come across so far I thought I'd just throw out here to see if anybody has had similar thoughts or experiences....
First up, the only reason I can think its overheated is that all the coolant had removed itself from the expansion tank. Before the incident I'd noticed that often, upon pulling up after a drive, the cooling system would burble and slowly trickle water down the overflow pipe in the front wheelarch which, to me, would point to the expansion tank being too small for the needs of the engine?? Surely the coolant should flow into the tank when hot, be stored there as long as required, then return to the swirl pot when the engine cools down again. For reference the cap is pressurised on the expansion, non-pressurised on the swirl (worms....can...??!!)
I'd never let the coolant get low, but the morning of the incident I had been sat in some traffic going into manchester, so wonder if the coolant had dripped out during this time and I just hadn't realised until it was too late? Anyway, question is - would a larger expansion tank help here??
Next up, I've got the heads off the car (one cracked...) and noticed something unusual about the head gaskets. Although the coolant galleries are dotted all over the head and the engine block, the gasket doesn't appear to follow the same pattern and actually blocks some of the galleries off (or restricts them severely):
Block:
With gasket...
You can see how the gasket blocks off many of the coolant holes. Surely this must affect the coolant flow around the head, but is this intentional/helpful/a complete mystery?? I've seen a couple of other photos (think there is one on deadpineapple) that show a similar gasket too.
Finally for now, I've just this evening taken delivery of a pair of used heads from a chap on the 'bay who deals with breaking Sierras, seing as one of mine became cracked due to the overheat. I asked him twice if they were 2.9 12v heads and he confirmed they were. However I've just been having a look and I've noticed that there are a couple of small differences, the main one of which is the seating of the rocker shafts being slightly different. On my original head, the shaft has 'feet' of a square-ish shape that mate with the head perfectly. The new heads I've just received have a different shape that doesn't match the rocker feet. However the rocker shaft will bolt down onto the new head ok and sit, from what I can see, in the same position against the valve stem. I'm just trying to weigh up if there would be any risk using the existing rockers on the new head. There are a couple of cast-markings on the heads and I can clearly make out a '90' on mine, and an '87' on the new ones - can just be seen in the pics. Does anybody know if these are date markings? (thus I'm trying to fit older heads to my engine). I've got to be honest as well, I'm a little disappointed with the state of the heads this chap has sent - they're pretty sludgy and have a few snapped studs stuck in the exhaust manifold bolt holes. Hey-ho.....
My original heads -
And the used ones I've just purchased -
Any thoughts appreciated!
Waterway holes (or lack of them) is normal, while I believe heads are not handed the gaskets are so correct one must go on left and right banks.
If you got rocker gear with heads I'd be inclined to use that, there is an oilway that goes up through one of the pedestals, this must obviously line up ! Not sure about the date thing but quite probable changes were made during the life of this engine to cut costs or make improvements.
good luck and if all else fails I know someone with a spare pair of heads ( clean and with NO broken studs)
How much did you say you paid for them ????
ETA look like 2.9 heads, 2.8 will only have two exhaust ports
If you got rocker gear with heads I'd be inclined to use that, there is an oilway that goes up through one of the pedestals, this must obviously line up ! Not sure about the date thing but quite probable changes were made during the life of this engine to cut costs or make improvements.
good luck and if all else fails I know someone with a spare pair of heads ( clean and with NO broken studs)
How much did you say you paid for them ????
ETA look like 2.9 heads, 2.8 will only have two exhaust ports
Edited by phillpot on Tuesday 19th October 21:30
Hi,
The gaskets are apparently intended to cover most of the holes - I initially thought that they were blocked when I looked at the over heating issue on mine. There was some gunge in the head channels but nothing of note.
The replacement heads you've got look like the early ones that were mainly used in the USA. They were prone to cracking and Ford redesigned them and the improved heads have the larger rocker mounts.
I never fully got to the bottom of why mine overheated but it might have been an airlock (never had one since so not convinced on that score) or more likely it was the replacement swirl pot pressure cap that resolved the issue. I only have about 1" of coolant in the reservoir, any more and it will overflow. I should add that the swirl pot is always full on mine now since I replaced the pressure cap many years ago but I did have to replace it last year iirc as it was leaking.
Jed
Edit: According to the Sven Pruett book the later (mid 88 onwards) heads had an 89TM casting number and rectangular rocker pedestal bosses. Earlier ones had oval shaped tower pedestals and an 86TM casting number.
The gaskets are apparently intended to cover most of the holes - I initially thought that they were blocked when I looked at the over heating issue on mine. There was some gunge in the head channels but nothing of note.
The replacement heads you've got look like the early ones that were mainly used in the USA. They were prone to cracking and Ford redesigned them and the improved heads have the larger rocker mounts.
I never fully got to the bottom of why mine overheated but it might have been an airlock (never had one since so not convinced on that score) or more likely it was the replacement swirl pot pressure cap that resolved the issue. I only have about 1" of coolant in the reservoir, any more and it will overflow. I should add that the swirl pot is always full on mine now since I replaced the pressure cap many years ago but I did have to replace it last year iirc as it was leaking.
Jed
Edit: According to the Sven Pruett book the later (mid 88 onwards) heads had an 89TM casting number and rectangular rocker pedestal bosses. Earlier ones had oval shaped tower pedestals and an 86TM casting number.
Edited by Jed-S on Tuesday 19th October 21:42
Thanks for the replies chaps.
I'm quite sure the heads are 2.9 because, as mentioned, there are 3 exhaust ports and my understanding is that the 2.8 had siamese ports on two of the cylinders each side.
However I'm still unsure as to why the gasket is as it is. The only reason I can think is so that it controls the flow around the head, forcing coolant right to the end of the head before it exits? However if it's something that's appeared before I guess I can accept it as normal (or at least TVR normal).
Jed, I initially thought an airlock may be the cause, mainly because of the burbling, bubbling noise each time the engine was stopped and allowed to cool. I tended to keep the swirl pot level just underneath the return hose from the engine, and would rarely have any fluid in the expansion tank until it rose and began to overflow, although I did keep a close eye on the level for a couple of months before deciding to let it do its own thing. I just think that if the expansion tank was larger, the coolant would be less likely to overflow from the system - anybody know if the Sierra/Granada tank is larger than the Triumph jobbie us S owners live with?
The more I think about it I'm really not sure about using the new heads, mainly due to the rocker shaft issue, but also with the amount of thick, black gloop thats crudding it up I'm not sure how hard a life they've had. I know they're second hand parts, but then again my engine isn't new either and the heads are in a much better condition (bar the crack!). This brings into question condition of the guides etc. and I don't want to be pulling it apart and doing the same thing again in 10k miles.
I've been kindly offered a replacement engine by a member on here, and I'm thinking it may be worth a full swap - the engine's coming out of mine anyway this weekend to replace the mounts.
I'm quite sure the heads are 2.9 because, as mentioned, there are 3 exhaust ports and my understanding is that the 2.8 had siamese ports on two of the cylinders each side.
However I'm still unsure as to why the gasket is as it is. The only reason I can think is so that it controls the flow around the head, forcing coolant right to the end of the head before it exits? However if it's something that's appeared before I guess I can accept it as normal (or at least TVR normal).
Jed, I initially thought an airlock may be the cause, mainly because of the burbling, bubbling noise each time the engine was stopped and allowed to cool. I tended to keep the swirl pot level just underneath the return hose from the engine, and would rarely have any fluid in the expansion tank until it rose and began to overflow, although I did keep a close eye on the level for a couple of months before deciding to let it do its own thing. I just think that if the expansion tank was larger, the coolant would be less likely to overflow from the system - anybody know if the Sierra/Granada tank is larger than the Triumph jobbie us S owners live with?
The more I think about it I'm really not sure about using the new heads, mainly due to the rocker shaft issue, but also with the amount of thick, black gloop thats crudding it up I'm not sure how hard a life they've had. I know they're second hand parts, but then again my engine isn't new either and the heads are in a much better condition (bar the crack!). This brings into question condition of the guides etc. and I don't want to be pulling it apart and doing the same thing again in 10k miles.
I've been kindly offered a replacement engine by a member on here, and I'm thinking it may be worth a full swap - the engine's coming out of mine anyway this weekend to replace the mounts.
as others have said, mine also runs with minimal coolant in the expansion tank, and about an inch below the neck in the swirl pot. If I put more in, it loses it again until it reaches that level, then it runs at that level for ages. It took me ages to realise that I should just stop filling it up!
The only times mine has blown out steam, has been because of a problem elsewhere: once it was the electric fan failing to cut in when stationary in traffic, and before that (when I first got the car) it would overheat because of a tiny split in the radiator that meant the system couldn't pressurise properly.
So I would be asking - did the cracked cylinder head cause the overheating, or did the overheating crack the head? I would suspect the former, but it depends where the crack is.
I would be wary about changing the heads for ones that aren't the same - it might be ok, but you don't know what other changes might have been made apart from the obvious ones.
The only times mine has blown out steam, has been because of a problem elsewhere: once it was the electric fan failing to cut in when stationary in traffic, and before that (when I first got the car) it would overheat because of a tiny split in the radiator that meant the system couldn't pressurise properly.
So I would be asking - did the cracked cylinder head cause the overheating, or did the overheating crack the head? I would suspect the former, but it depends where the crack is.
I would be wary about changing the heads for ones that aren't the same - it might be ok, but you don't know what other changes might have been made apart from the obvious ones.
Perhaps your coolant loss was due to the cracked head over-pressurising your coolant system ? I doubt you need a larger expansion tank.
Again perhaps, if your pressure cap was not allowing the return of coolant from the expansion tank due to a dodgy seal on the return ? then as the coolant overheated due to the crack and overflowed into the expansion tank (at pressure due to the crack) then it would have nowhere to go but out of the overflow to atmosphere ?
the crack has got to be the root cause of your problem so I would tend to fix that, check everything else and see how it goes.
good luck
K
Again perhaps, if your pressure cap was not allowing the return of coolant from the expansion tank due to a dodgy seal on the return ? then as the coolant overheated due to the crack and overflowed into the expansion tank (at pressure due to the crack) then it would have nowhere to go but out of the overflow to atmosphere ?
the crack has got to be the root cause of your problem so I would tend to fix that, check everything else and see how it goes.
good luck
K
ketvrin said:
I'm waiting for Mark to come along any minute and correct my thermo-dynamic theory and shoot me out of the sky again 
but we all know he's a closet pressure-cap-on-the-swirl-tank kind of guy now after being "converted" at SCH
K
I'm with you professor! Sometimes it's difficult to separate cause and effect. Or chickens and eggs. Or plain and pressurised caps. but we all know he's a closet pressure-cap-on-the-swirl-tank kind of guy now after being "converted" at SCH K
pie2k1 said:
For reference the cap is pressurised on the expansion, non-pressurised on the swirl (worms....can...??!!)
Knew that discussion wasn't lurking far away....!Anyway, yes the car was getting hot in traffic the morning prior to the overheat. My worry is that it's boiled off most of the coolant leaving next to nil in the system, thus causing temps to go up.
My suspicion is that this caused the head to crack, as the week before when I checked the oil there was no 'mayo' under the filler cap. If water was getting away through a crack I would also expect oil contamination to some degree. Just my current thought, not saying its right. And would also depend on when the crack developed.
The crack itself is directly above the spark plug, from the top of the head down towards the plug hole, on the RH plug looking at the exhaust manifold (can't remember if its the left or right head).
Anywho, I think I'm going to ditch the new heads, probably not worth the mither (and worry), and I'll try for correct heads or a nice new engine.
pie2k1 said:
If water was getting away through a crack I would also expect oil contamination to some degree. Just my current thought, not saying its right. And would also depend on when the crack developed.
Not necessarily. If the crack joins an oilway and a water channel, then you might get water in the oil or vice versa. If the crack goes from a waterway into the compression chamber, but doesn't touch an oilway, you'll still get overheating (due to compression gasses in the coolant) but you wouldn't get any water reaching the oil.oil contamination is a sign that there may be a head gasket problem. Lack of oil contamination doesn't necessarily mean there isn't!
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