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Diagnosis of blue smoke on hard acceleration.

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HI everyone,

I have recently done an engine swap in my xr 6 turbo ute, long story short i bought the ute it then only got 300kms down the road and decided to let a piece of piston 6 go and it destroyed my motor.

So i sourced a good low km motor and replaced everything else, new cooling system, fuel system, turbo, exhaust so that i was starting form scratch.

I had my tuner run it up on the dyno to check the condition of the motor before putting any more power through it.

Upon doing so he found that the engine blew a lot of blue smoke under hard acceleration. so my first question is i want to diagnose the problem properly before replacing the engine under warranty.

Symptom: blue smoke under hard acceleration that clears after iding for a minute or two. He said he also noticed my oil pressure gauge went right around to 100psi on my aftermarket gauge in the car.

Possible problems:

Rings, im thinking that the rings are possibly worn and im getting blow by under load.

Valve stem seals leaking under load?

Possible problem with the oil pump not relieving pressure.

The main question is i want to diagnose it properly and i am thinking i put a master oil pressure gauge in and double check oil pressure. Cylinder leak down test and maybe another compression test to see the condition of the rings?

Vehicle is a Ford BF MK2 xr6 turbo ute.


Your problem can be a little tricky to accurately diagnose as there are a few potential causes for the smoke you're seeing. If the blue smoke is under sustained acceleration then it's unlikely to be valve guide seals - These tend to show up after going back onto the throttle after being under high vacuum in over run. Worn rings however can result in what you're seeing from two aspects:

1. Excessive blow by past the rings resulting in oil vapour entering the intake system from the breather system. Check the intake system for excessive oil coming from the rocker cover breathers/PCV system as a guide here.

2. Worn rings allowing oil to directly enter the combustion chambers.

I'd suggest checking the oil pressure with a reliable gauge, although I wouldn't be worried about oil pressure exceeding 100 psi during cold startup - this is quite normal. Once the engine is up to operating temperature though and the oil is hot you should see no more than perhaps 60-80 psi at redline (a very approximate guide is 10 psi per 1000 rpm).

I'd start with a compression and leak down test and see what that reveals. in my own experience unless there is half a piston that's damaged, you often won't see massive variations in the leak down or compression numbers, and getting a feel for these results will really need some familiarity with these engines.

Depending on how many miles you have done since the engine swap and also how bad the blow up of the old motor was , its possible there could be a lot of oil in the silencers which will only burn out the heat is at its max ie full load , if this is the case and all other checks prove ok it will burn off ....eventually..

Cheers Keith

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