1.5 diesel questions

[posscakes]

i got an old passat diesel. I just had the cylinder head overhauled and a new head gasket put in by a mechanic recently. but i still have a few worries with the motor. when you start her up she spits wet oil out the exhaust pipe. Also when the motor idles or is at low revs the oil light starts to illuminate sort of dimly. i've checked the oil levels on the dip stick before firing her up in the morning seem to be fine also the motor started making a funny knock on the way home today. not running rough or anything just making a funny knock. where to next? any help appreciated.

[brackie]

Good to see you back.
You have to be able to differentiate between a diesel knock and a big end/small end etc knock. Diesel knock is normal in these motors a long as it's not extreme. The oil light may or may not be telling the truth and the only way to be sure is to connect a gauge to the motor. Oil appearing at the exhaust is a worry. While the head was off I would have pushed out the pistons and checked the bores and rings for wear and other problems. It's diffficult to diagnose by remote control but the mechanic that did the head job for you should have checked the motor out thoroughly.
The bottom end of these motors are bullet proof but if it's clocked up a lot of km and hasn't been well maintained the rings could be cactus. How does it start? Does it have good compression?

[smithy010]

Is that the one that was on ebay a month or so ago?

Sounds like rings.... Get a compression test.

[gldgti]

low oil pressure at idle (making oil light come on) is a big end/and/or crank bearing wear issue...

i have found that an OK method to find roughly where the noise is coming from is to place a long, large flat screwdriver against the block in different places when its running, and place your ear next to the end of the handle (plastic handled screw driver). you may be able to find which cylinder it is coming from...

dont rule out the piston hitting the valves or the head either - dads discovered this in 2 engines in the last month!!!

good luck

aydan

[smithy010]

The "Aydan Special" Stethoscope.. I like it!

[brackie]

dont rule out the piston hitting the valves or the head either - dads discovered this in 2 engines in the last month!!!

Are you sure the mechanic used the correct head gasket? This is crucial when refitting a diesel head. The number of notches denotes the thickness. Too few notches = too thin a gasket and so piston(s) could hit the valves.

[gldgti]

Are you sure the mechanic used the correct head gasket? This is crucial when refitting a diesel head. The number of notches denotes the thickness. Too few notches = too thin a gasket and so piston(s) could hit the valves.

FYI - everyone. be very careful when measuring piston projection above the block. do it accurately. also note that sometimes this itself is not enough, and the tolerances in the bearings from the main, big end, gudgeon can add up in one direction so that your piston is lightly tapping the head.

please, always err on the side of caution. get a thicker head gasket if your not sure.... the lower ocmpression will only be a disadvantage on starting.. and will be better at all other times.

[posscakes]

"funny knock" turned out to be the choke tappin on the firewall. still heaps of oil left over in the coolant from when the gasket was replaced, been trying to flush it out. cleaned the plastic reservoir on the firewall with mineral turps pretty good but not sure wether it safe to flush the coolant system out with turps. any ideas??? edison sorry i ain't sent the gasket yet.

[syncro]

What brand of oil filter do you have?

[brackie]

You need to get ALL of that oil out of the cooling system. It will cause all kinds of problems including blocking the radiator and heater cores. My advice would be to remove the thermostat and get the system powerflushed at a radiator specialist's place.

Phill's question probably is connected with the brand of filter and whether or not it has an anti-fallback valve. I'm sure he will agree that OEM is best.