Head gaskets and cylinder liner issues.
Discussion
My Griffith 500 (1996 serp) has recently suffered from a mystery misfire and gradual loss of coolant. All hoses were checked, coolant topped up and system bled. A few days ago the temperature started to go up alarmingly to near 100 degrees so I pulled in promptly and switched off. On opening the bonnet it was in the process of dumping all of the coolant onto the floor at great pressure!!!!
Later when topped up, bled and re-started it quickly built up pressure again, fans worked fine gauge worked fine but it proceeded to vent coolant again. Incidentally, car has never had cooling issues before.
I assumed the worst, removed all components in readiness for head removal, noted that one exhaust port was totally clean (steam cleaned!) so assumed head gasket or liner issues and today proceeded to remove both heads. Now, this may have been a mistake as there is no evidence of either issues. Engine appears in very good condition, gaskets and faces seem fine and liners do not seem to have moved, also no evidence of a steam cleaned cylinder!!! What else could be wrong?? The only potential issue that I see is that one combustion chamber has a strange clean fan pattern between the valves - could this be a crack and if so would it cause system pressurisation?
I will take pictures tomorrow and try to remove those valves but meantime any comments, suggestions appreciated. I may have jumped to conclusions and wasted a lot of time on this but not a big issue as it gives me an opportunity to de-coke and freshen up the engine generally (I will be checking the cam although it too at first impression looks ok)
Later when topped up, bled and re-started it quickly built up pressure again, fans worked fine gauge worked fine but it proceeded to vent coolant again. Incidentally, car has never had cooling issues before.
I assumed the worst, removed all components in readiness for head removal, noted that one exhaust port was totally clean (steam cleaned!) so assumed head gasket or liner issues and today proceeded to remove both heads. Now, this may have been a mistake as there is no evidence of either issues. Engine appears in very good condition, gaskets and faces seem fine and liners do not seem to have moved, also no evidence of a steam cleaned cylinder!!! What else could be wrong?? The only potential issue that I see is that one combustion chamber has a strange clean fan pattern between the valves - could this be a crack and if so would it cause system pressurisation?
I will take pictures tomorrow and try to remove those valves but meantime any comments, suggestions appreciated. I may have jumped to conclusions and wasted a lot of time on this but not a big issue as it gives me an opportunity to de-coke and freshen up the engine generally (I will be checking the cam although it too at first impression looks ok)
I have just had to deal with a pretty identical issue : missfire, coolant pressurised and being lost internally, steam cleaned exhaust port. I hoped that it was the head gasket or porous head but after removing the head finding the gasket pristine and having the head pressure tested with no leaks, I had to accept that it was a liner / block leak. I had top hat liners fitted and have just completed the engine rebuild and currently running it in. Let me know if you need some info or guidance.
I had a crack in my exhaust port on my old griff 500
.. the porting had broken into the water jacket .. was was 3 years old at the time and was as it left the factory.
Not an easy one to spot and pottentially harder with the head removed.
As you have it all apart - it's worth checking if any of the liners looks lower than the others and for any tell tale signs of water seeping up between the block and liner.
.. the porting had broken into the water jacket .. was was 3 years old at the time and was as it left the factory.
Not an easy one to spot and pottentially harder with the head removed.
As you have it all apart - it's worth checking if any of the liners looks lower than the others and for any tell tale signs of water seeping up between the block and liner.
I had a more thorough look yesterday and the liners are all the same level, definitely no sign of movement and nor is there any sign of any seepage past any of them - not ruling this out but feeling is unlikely to be the issue. Gaskets look fine.
Tops of pistons do not look steam cleaned, although I guess if only started recently then there may not have been time for all deposits to be removed.
This leaves the only main concern being that some of the exhaust ports are virtually spotless whereas some have a general layer of carbon in them. If it was pinholes in the port it would be a huge coincidence that a few had failed would it not?????
The car has been running down on power for a while with a misfire and lambda outputs have been very slow in their cycling - could a weak/rich mixture or serious ignition issue cause the ports to overheat due to weak mixture or be cleaned by excess fuel? Pre-cats look a bit grey rather than white and a lot of soot in there and in the y piece. Still does not explain dumping of coolant unless that really was a coincidence although cannot see why, hoses, rad fine, thermostat was tested yesterday and opens fine - cannot see how a big airlock would have suddenly appeared????
This poor power and running was thought to possibly be a worn cam but on initial inspection all lobes seem fine!
I will try to find a way of hosting some photos in order to be able to post theme here.
Thank you for all comments so far - this is going to be a tricky one and although I am capable of doing whatever is involved I obviously do not wish to spend money unnecessarily.
Tops of pistons do not look steam cleaned, although I guess if only started recently then there may not have been time for all deposits to be removed.
This leaves the only main concern being that some of the exhaust ports are virtually spotless whereas some have a general layer of carbon in them. If it was pinholes in the port it would be a huge coincidence that a few had failed would it not?????
The car has been running down on power for a while with a misfire and lambda outputs have been very slow in their cycling - could a weak/rich mixture or serious ignition issue cause the ports to overheat due to weak mixture or be cleaned by excess fuel? Pre-cats look a bit grey rather than white and a lot of soot in there and in the y piece. Still does not explain dumping of coolant unless that really was a coincidence although cannot see why, hoses, rad fine, thermostat was tested yesterday and opens fine - cannot see how a big airlock would have suddenly appeared????
This poor power and running was thought to possibly be a worn cam but on initial inspection all lobes seem fine!
I will try to find a way of hosting some photos in order to be able to post theme here.
Thank you for all comments so far - this is going to be a tricky one and although I am capable of doing whatever is involved I obviously do not wish to spend money unnecessarily.
We did the plug test on my car at weekend.. and they did differ a bit due to air flow etc.. although looking at the exhaust ports last time I had the manifolds off, they all showed similar.. If you run your finger around them you should pick up a bit of soot I would have said...
Is the variation all on the same bank or both? May be air flow / fueling causes some change pot to pot... .But the clean one and fan pattern... this sounds like the presurisation point?...
Some pics would help...
Is the variation all on the same bank or both? May be air flow / fueling causes some change pot to pot... .But the clean one and fan pattern... this sounds like the presurisation point?...
Some pics would help...
Edited by TVR Beaver on Monday 2nd November 11:51
I had a quick look. The odd bit is the clean area between the inlet and exhaust valve, but its only 4 or 5mm wide, and there is no soot at all. This is on the same cylinder as with the "clean port". I suppose it would be possible for water / steam to clean the valves from the ports at overlap? The cooling system had been highly pressurised, but I dont think a crack in a port could produce this much pressure.
blitzracing said:
The cooling system had been highly pressurised, but I dont think a crack in a port could produce this much pressure.
Do you somehow think the pressure is derived from the compression in the cylinder?loss of coolant, more heat/cc, coolant boils, big pressure .. as I understand it.
How can you tell it's been 'highly pressurised'?... what gives this away?.... But would agree... a hole / crack in a port should not cause this amount of pressure.... But coolant loss and boiling may?
With regards to getting in at crossover... you can find bits in all pot's if an engine goes pop on just one... so may be possable, and could impact other exhaust ports on the same bank??
With regards to getting in at crossover... you can find bits in all pot's if an engine goes pop on just one... so may be possable, and could impact other exhaust ports on the same bank??
Edited by TVR Beaver on Monday 2nd November 13:28
If it was all back together I'd suggest a leakdown test and HC test. If you don't mind some extra work to put it back together (and then take it apart *again* when you've found the problem) that still might be the best way to locate the leak. Leak testing the individual components is going to be quite tricky I would have thought.
I am no expert but I would say the the ones that look clean are Ok and the ones that look black have the problem not the other way round. Looks to me like you have a fueling issue and at least a couple of cylinders are running way to rich.
Like I say I am no expert and could be completely wrong so best wait for the guru's to reply.
Chris
Like I say I am no expert and could be completely wrong so best wait for the guru's to reply.
Chris
It has been down on power for a while, bad misfire on start up and lambda switching is very slow. Cam wear was considered a culprit but lobes actually look good (although not measured yet). There is a chance that there is a fueling problem and the coolant loss was conincedental and due to a seperate issue.
Short of the injectors, fuel side has been checked out with lambda switching only noted symptom - lambdas were replaced but no change. Coolant was changed last year, all hoses checked recently and no leaks apparent. Car has always been perfectly behaved coolant wise until recently (around 3,000 miles in last year)
Short of the injectors, fuel side has been checked out with lambda switching only noted symptom - lambdas were replaced but no change. Coolant was changed last year, all hoses checked recently and no leaks apparent. Car has always been perfectly behaved coolant wise until recently (around 3,000 miles in last year)
JKY said:
lambda switching is very slow.
To my mind that points firmly towards a lazy (blocked) lambda sensor, there's no other likely explanation. Possibly some other fault has caused the new ones to fail in the same way as the old ones.Although I haven't been able to see any effects on the logs, I was told that water injection would cause the lambda sensors to misread. Also if the amount of water is sufficient to get liquid water onto the hot element of the lambda sensor the thermal shock can destroy the sensor.
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