Technical Fiat Siena, 1.6 (16 valve) engine low compression after replacement of head gasket and extensions/rocker box/camboxes

[Riaan2001]

Could someone please give me some guidance on this one, I have replaced the cylinder head gasket on this 1.6, 16 valve fiat engine and now struggling with a low compression issue where the engine refuses to start.
The engine was running but had an internal coolant leakage on cylinder 1, therefore having replaced the head gasket.
Now after having purchased the timing tool kit, I set the cam timing as it should be, but still not able to start.
With a compression tester, it shows low compression on cylinders 1,2 and 3.
The valves are NOT bent, postons and rings are good.
It sounds like incorrect timing, however. I did set the timing with a timing kit on the cams, so I'm at a loss for words on this one.
Am I missing something or perhaps doing something wrong?

 

[bugsymike]

Could someone please give me some guidance on this one, I have replaced the cylinder head gasket on this 1.6, 16 valve fiat engine and now struggling with a low compression issue where the engine refuses to start.
The engine was running but had an internal coolant leakage on cylinder 1, therefore having replaced the head gasket.
Now after having purchased the timing tool kit, I set the cam timing as it should be, but still not able to start.
With a compression tester, it shows low compression on cylinders 1,2 and 3.
The valves are NOT bent, postons and rings are good.
It sounds like incorrect timing, however. I did set the timing with a timing kit on the cams, so I'm at a loss for words on this one.
Am I missing something or perhaps doing something wrong?

If the head gasket failed due to overheating, then there is a good chance the cylinder head and engine block are warped, unless they were checked and skimmed flat of course.
I would also check for the reason the engine overheated in the first place.
Apart from that the overheating often affects the piston/cylinder sealing.
When cylinder head was off I usually pour an equal amount of oil down each cylinder bore with pistons at same height and if any drain away quicker or different speed to the others overnight I would be suspicious of the piston /bore seal.
Equally when head off and valves shut (spark plugs in) it is possible to pour petrol into the combustion chambers and if valves not sealing it will drain past the valves and out of the manifolds to show you.
Only if after all that correctly reassembled would I check valve timing etc.
If you are sure 100% that the timing is correct and still getting low compression readings, then I would do a "leak test".
This involves putting compressed air into each cylinder one at a time using a air line adaptor with the cylinder being tested locked on the firing stroke at TDC so valves closed. The engine must not turn as this allows valves to open.
This test will show if pistons are not sealing (air escaping from the oil filler), air past the valves (into the manifolds via air cleaner or exhaust pipe), also if water coolant cap off and filled to the brim then the cylinder gasket/head/block seal (water will start to overflow from coolant tank).

 

[Riaan2001]

If the head gasket failed due to overheating, then there is a good chance the cylinder head and engine block are warped, unless they were checked and skimmed flat of course.
I would also check for the reason the engine overheated in the first place.
Apart from that the overheating often affects the piston/cylinder sealing.
When cylinder head was off I usually pour an equal amount of oil down each cylinder bore with pistons at same height and if any drain away quicker or different speed to the others overnight I would be suspicious of the piston /bore seal.
Equally when head off and valves shut (spark plugs in) it is possible to pour petrol into the combustion chambers and if valves not sealing it will drain past the valves and out of the manifolds to show you.
Only if after all that correctly reassembled would I check valve timing etc.
If you are sure 100% that the timing is correct and still getting low compression readings, then I would do a "leak test".
This involves putting compressed air into each cylinder one at a time using a air line adaptor with the cylinder being tested locked on the firing stroke at TDC so valves closed. The engine must not turn as this allows valves to open.
This test will show if pistons are not sealing (air escaping from the oil filler), air past the valves (into the manifolds via air cleaner or exhaust pipe), also if water coolant cap off and filled to the brim then the cylinder gasket/head/block seal (water will start to overflow from coolant tank).

Thank you, I will do these checks and see if this reveals a possible culprit then.

 

[Riaan2001]

Thank you, I will do these checks and see if this reveals a possible culprit then.

If the head gasket failed due to overheating, then there is a good chance the cylinder head and engine block are warped, unless they were checked and skimmed flat of course.
I would also check for the reason the engine overheated in the first place.
Apart from that the overheating often affects the piston/cylinder sealing.
When cylinder head was off I usually pour an equal amount of oil down each cylinder bore with pistons at same height and if any drain away quicker or different speed to the others overnight I would be suspicious of the piston /bore seal.
Equally when head off and valves shut (spark plugs in) it is possible to pour petrol into the combustion chambers and if valves not sealing it will drain past the valves and out of the manifolds to show you.
Only if after all that correctly reassembled would I check valve timing etc.
If you are sure 100% that the timing is correct and still getting low compression readings, then I would do a "leak test".
This involves putting compressed air into each cylinder one at a time using a air line adaptor with the cylinder being tested locked on the firing stroke at TDC so valves closed. The engine must not turn as this allows valves to open.
This test will show if pistons are not sealing (air escaping from the oil filler), air past the valves (into the manifolds via air cleaner or exhaust pipe), also if water coolant cap off and filled to the brim then the cylinder gasket/head/block seal (water will start to overflow from coolant tank).

I ended up stripping the entire engine again to check everything over, I bought new piston rings again and did a full re-assembly, bought another cylinder head and took it to engineering where all the valve guides and valves were replaced to make sure there is no substitute. New head gasket etc.
I found that some of the hydraulic lifters seemed to have been clogged and not releasing, so I ended up replacing them as well, all the hydraulic lifters.
Now after re-assembly, I again used the timing tool to set the timing and found the exact same problem, No Compression.
Is it necessary to prime the hydraulic lifters before assembly, because this is the only thing I can think of that will still be causing this kind of issue?
Although it will be senseless seeming the cam-boxes goes last and will press the valves open if all these lifters are filled with oil, OR, is this perhaps what needs to be done?
Alternatively, I'm open for suggestions.

 

[bugsymike]

I ended up stripping the entire engine again to check everything over, I bought new piston rings again and did a full re-assembly, bought another cylinder head and took it to engineering where all the valve guides and valves were replaced to make sure there is no substitute. New head gasket etc.
I found that some of the hydraulic lifters seemed to have been clogged and not releasing, so I ended up replacing them as well, all the hydraulic lifters.
Now after re-assembly, I again used the timing tool to set the timing and found the exact same problem, No Compression.
Is it necessary to prime the hydraulic lifters before assembly, because this is the only thing I can think of that will still be causing this kind of issue?
Although it will be senseless seeming the cam-boxes goes last and will press the valves open if all these lifters are filled with oil, OR, is this perhaps what needs to be done?
Alternatively, I'm open for suggestions.

It sounds like you may misunderstand the hydraulic lifter operation.
Generally if old hydraulic tappets ran quiet before working/rebuilding engine I would wipe off the old ones and leave them in a tray of engine oil in their correct order in the engine. If using the old ones always fit in the order they came out!
If you allow the oil to drain out then they will not operate until oil has filled them from the engine's oil pressure system again as they have a ball valve inside them which allows them to self adjust.
So when they are firm when you try and squash them with your fingers then they are probably working correctly, if you squeeze them in a vice or wash them in a cleaning tank you will stop them working, so best left alone.
If fitting a new set I would leave them soaking in engine oil over night to prime them, so when you install them they will start to work promptly especially as they will have new ball valves inside.
Generally faulty ones rattle when engine is running as they ball valves don't work, hence they cannot fill up with oil to function as intended.
If you are 100% sure nothing else is wrong with engine I would make sure engine oil level is correct then with spark plugs removed spin engine over for a bit, let it rest and spin again and so on and it should gradually get oil into the lifters so they start to work allowing valves to open and shut correctly and start to get compression back.
Do not just flog engine over and over or you will be buying a new starter as well.!!!

 

[Riaan2001]

It sounds like you may misunderstand the hydraulic lifter operation.
Generally if old hydraulic tappets ran quiet before working/rebuilding engine I would wipe off the old ones and leave them in a tray of engine oil in their correct order in the engine. If using the old ones always fit in the order they came out!
If you allow the oil to drain out then they will not operate until oil has filled them from the engine's oil pressure system again as they have a ball valve inside them which allows them to self adjust.
So when they are firm when you try and squash them with your fingers then they are probably working correctly, if you squeeze them in a vice or wash them in a cleaning tank you will stop them working, so best left alone.
If fitting a new set I would leave them soaking in engine oil over night to prime them, so when you install them they will start to work promptly especially as they will have new ball valves inside.
Generally faulty ones rattle when engine is running as they ball valves don't work, hence they cannot fill up with oil to function as intended.
If you are 100% sure nothing else is wrong with engine I would make sure engine oil level is correct then with spark plugs removed spin engine over for a bit, let it rest and spin again and so on and it should gradually get oil into the lifters so they start to work allowing valves to open and shut correctly and start to get compression back.
Do not just flog engine over and over or you will be buying a new starter as well.!!!

Ah, that makes perfect sense, thank you for the clarity on this one.
I will do just that, thank you once again.