So, I finished my project car, and an engine died on me. At first it gave me missfires, and then it wouldnt start at all.. Which lead me to measure compression. I measured around 5 bar across all cylinders but cylinder nr.3 which had 7.5 bar and only on this cylinder engine would give some starting sings...
I decided to pull an engine apart and rebuild it so i had a good car at the end...
What I found surprised me.
All rings were same worn, 0.95mm which is worn yes, but not that worn to give so low compression... whats more interesting is that valves on cylinder nr 3 were in worst shape, exhaust valve was very leaky...
Compare this to cylinder nr.2 which had good valves with no leaks, same piston ring gaps yet lowest compression... it makes no sense to me... Head gasket did not leak, it was good.
I have called a man that works as CNC turner (if its called like that) and both of us could not find the main problem which caused so low compression... Cylinders were oval only 0.02mm and were in great shape, measured by that same man...Traces of honing are still very visible.
I have tried to brake rings to see if they lost tension but they snapped quickly like a glass...
Watter in cooling system was clean, no oil traces nor i saw bubbles coming out. Level was pretty steady when i was cranking the engine.
When I could not think of anything else, i decided to rebuild an engine.
New spark plugs
Used but like new distributor, new rotor
New belts, new tensioner, all new gaskets
New rod bearings, new piston rings
I gave head for inspection and paid complete work on it. Everything was either changed or renewed.
Bought new Goetze piston rings (could not find mahle at local stores)
With new rings, ring gap across cylinders was from 0.45mm to 0.55mm, and I have installed them correctly, checking tapered side of it to face upwards... so stamping mark was not stamped wrong.
By bentley manual factory ring gap for this engine should be from 0.30 to 0.50mm so i guess mine was fine...
I have checked timing belt before and it did not skip a tooth, bought a new one also upon rebuilding an engine.
When I have assembled it, it started just fine. And i was driving it for like 10 days at most... It then started doing the same as it did before it died like last time... Smoked blue and lots of missfires...One day i parked it, and after 5 hours i could not start it again...
I have measured compression again and i have measured it low, from 4.5 to 5bar across all cylinders...
When i poured oil inside them compression jumped to 9 bar shortly.
Which gave me conclusion that rings were leaking probably...
I did not believe they broke, as before rebuild i had same problem.
At the end of the day, after i checked timing, ensured valve clearances were good, and valves not leaking, head gasket not failing, i had no options but to pull everything apart once again.
And i have not found anything wrong.
The only thing i did found is that piston ring gaps were not rotated from one to another for 120 degrees but more less, like 30 or so. And its the same for every piston.
Also i have found some very little metal particles in cylinders, and inside 5th i think, it left tiny and short mark on cylinder wall. I am not happy but not so concerned at same time as its really tiny. I can not also find where these particles came from.
Perhaps i am not able to find or see the problem, so i am seeking for help everywhere...
So far few good mechanics are clueless what could have gone wrong.
I can post some pictures if you like and if you guys are willing to help that is...
Thank you in advance.
Cheers, Tom.
I decided to pull an engine apart and rebuild it so i had a good car at the end...
What I found surprised me.
All rings were same worn, 0.95mm which is worn yes, but not that worn to give so low compression... whats more interesting is that valves on cylinder nr 3 were in worst shape, exhaust valve was very leaky...
Compare this to cylinder nr.2 which had good valves with no leaks, same piston ring gaps yet lowest compression... it makes no sense to me... Head gasket did not leak, it was good.
I have called a man that works as CNC turner (if its called like that) and both of us could not find the main problem which caused so low compression... Cylinders were oval only 0.02mm and were in great shape, measured by that same man...Traces of honing are still very visible.
I have tried to brake rings to see if they lost tension but they snapped quickly like a glass...
Watter in cooling system was clean, no oil traces nor i saw bubbles coming out. Level was pretty steady when i was cranking the engine.
When I could not think of anything else, i decided to rebuild an engine.
New spark plugs
Used but like new distributor, new rotor
New belts, new tensioner, all new gaskets
New rod bearings, new piston rings
I gave head for inspection and paid complete work on it. Everything was either changed or renewed.
Bought new Goetze piston rings (could not find mahle at local stores)
With new rings, ring gap across cylinders was from 0.45mm to 0.55mm, and I have installed them correctly, checking tapered side of it to face upwards... so stamping mark was not stamped wrong.
By bentley manual factory ring gap for this engine should be from 0.30 to 0.50mm so i guess mine was fine...
I have checked timing belt before and it did not skip a tooth, bought a new one also upon rebuilding an engine.
When I have assembled it, it started just fine. And i was driving it for like 10 days at most... It then started doing the same as it did before it died like last time... Smoked blue and lots of missfires...One day i parked it, and after 5 hours i could not start it again...
I have measured compression again and i have measured it low, from 4.5 to 5bar across all cylinders...
When i poured oil inside them compression jumped to 9 bar shortly.
Which gave me conclusion that rings were leaking probably...
I did not believe they broke, as before rebuild i had same problem.
At the end of the day, after i checked timing, ensured valve clearances were good, and valves not leaking, head gasket not failing, i had no options but to pull everything apart once again.
And i have not found anything wrong.
The only thing i did found is that piston ring gaps were not rotated from one to another for 120 degrees but more less, like 30 or so. And its the same for every piston.
Also i have found some very little metal particles in cylinders, and inside 5th i think, it left tiny and short mark on cylinder wall. I am not happy but not so concerned at same time as its really tiny. I can not also find where these particles came from.
Perhaps i am not able to find or see the problem, so i am seeking for help everywhere...
So far few good mechanics are clueless what could have gone wrong.
I can post some pictures if you like and if you guys are willing to help that is...
Thank you in advance.
Cheers, Tom.
Comment