Melted piston crown on Peugeot 1.9 8v engine
Posted: October 27th, 2010, 12:36 am
Hi !
Dear Guy , it's been a while since my last posting here , do hope you're well .
As always , please , need your help/assistance with this one :
I'm trying to help one of our forum members fixing and diagnosing engine issues .. well , diagnosing the most (hes already decided to skip fixing this engine , which is good choice , and fitting a used one instead ..)
The car/engine is : Peugeot 205 GTi with 1.9 8v engine (XU9JA D6B , compression ration 9.8 , Bosch LE Jetronic engine management with mechanical ignition i.e. distributor ..) .. the engine is standard , so no modifications .
Complains where that one day , during the motorway run , upon accelerating harder "something went inside the engine" , couped with loads of white smoke from exhaust and oil leaking everywhere around the engine (from the head to block base joint , head gasket area ..)
He reported that afterwards there was - no coolant loss , coolant and oil temp. was normal and oil pressure normal.
Engine running history - said that it was good , apart from using smaller amounts of oil , that the spark plugs where oily and particularly spark plug from 4-th cylinder (2 Bar compression) which had a thick oily carbon deposit .
So i suggested compression and leak test , compression test done with the results as follows :
Cylinder
No.1 - 11 Bar
No.2 - 12 Bar
No.3 - 10 Bar
No.4 - 2 Bar
They removed the head and found this :
(sorry , i do not have better pictures than this ones !)
Melted piston crown on cylinder No.4 .
My assumptions why did this piston melt are : uncontrolled combustion - excessive heat (because it's molten off the edge areas towards the center ..) , or lean mixture on this cylinder because partially blocked fuel injector , wrong/few grade hotter spark plug , leaky inlet manifold gasket (which caused this cylinder to go lean) , cracked head or liner (cylinder lubrication diluted by coolant ..) , some kind of valve/valve seat problem .
I do insist on chasing the cause of this problem because all the engine management fueling and ignition components from this blown engine will be reused on the "new" one , and if it's a bad injector or something fueling/ignition wise it can damage this the new second hand engine as well , so i recommended :
1 Injectors testing (marking this injector from the affected cylinder especially) on ultrasonic machine - resistance measuring first , then leak/pressure test , then spray pattern/volume test ... then cleaning .
2 Spark plug inspection - in case if they've had by any chance a few grade hotter spark plug on this cylinder .
3 Head inspection - combustion chamber for discoloration , valves/valve seats for improper sealing , cracks .
4 Inlet manifold - gasket inspection .
What might happened with this causing piston crown melting ?
Thanks !
Kind regards
Damir
Dear Guy , it's been a while since my last posting here , do hope you're well .
As always , please , need your help/assistance with this one :
I'm trying to help one of our forum members fixing and diagnosing engine issues .. well , diagnosing the most (hes already decided to skip fixing this engine , which is good choice , and fitting a used one instead ..)
The car/engine is : Peugeot 205 GTi with 1.9 8v engine (XU9JA D6B , compression ration 9.8 , Bosch LE Jetronic engine management with mechanical ignition i.e. distributor ..) .. the engine is standard , so no modifications .
Complains where that one day , during the motorway run , upon accelerating harder "something went inside the engine" , couped with loads of white smoke from exhaust and oil leaking everywhere around the engine (from the head to block base joint , head gasket area ..)
He reported that afterwards there was - no coolant loss , coolant and oil temp. was normal and oil pressure normal.
Engine running history - said that it was good , apart from using smaller amounts of oil , that the spark plugs where oily and particularly spark plug from 4-th cylinder (2 Bar compression) which had a thick oily carbon deposit .
So i suggested compression and leak test , compression test done with the results as follows :
Cylinder
No.1 - 11 Bar
No.2 - 12 Bar
No.3 - 10 Bar
No.4 - 2 Bar
They removed the head and found this :
(sorry , i do not have better pictures than this ones !)
Melted piston crown on cylinder No.4 .
My assumptions why did this piston melt are : uncontrolled combustion - excessive heat (because it's molten off the edge areas towards the center ..) , or lean mixture on this cylinder because partially blocked fuel injector , wrong/few grade hotter spark plug , leaky inlet manifold gasket (which caused this cylinder to go lean) , cracked head or liner (cylinder lubrication diluted by coolant ..) , some kind of valve/valve seat problem .
I do insist on chasing the cause of this problem because all the engine management fueling and ignition components from this blown engine will be reused on the "new" one , and if it's a bad injector or something fueling/ignition wise it can damage this the new second hand engine as well , so i recommended :
1 Injectors testing (marking this injector from the affected cylinder especially) on ultrasonic machine - resistance measuring first , then leak/pressure test , then spray pattern/volume test ... then cleaning .
2 Spark plug inspection - in case if they've had by any chance a few grade hotter spark plug on this cylinder .
3 Head inspection - combustion chamber for discoloration , valves/valve seats for improper sealing , cracks .
4 Inlet manifold - gasket inspection .
What might happened with this causing piston crown melting ?
Thanks !
Kind regards
Damir