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P0304 and 305

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo's stylish, distinctive "P2" platform cars.

2001 - 2007 V70
2004 - 2007 V70 R
2001 - 2007 XC-70
2001 - 2009 S60
2003 - 2007 S60 R

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Re: P0304 and 305

Post by SuperHerman » Tue Jan 14, 2020 10:04 pm

Quick and dirty test is to put a cap full of oil in #4 and #5 and see if you can exclude the valves. If it works, then put some Seafoam in the pistons a few times over the course of a few days and see if it frees up the rings. Don't put more than 1/2 a treatment total so you don't ruin your oil and you can keep working on it by driving.

If it is the valves, I would source an engine and see what you think of the price and work. Once you are comfortable keeping the car, I would pull the head and see what you find. Personally in my garage I would rather pull a head than an engine. Some would rather pull the engine. Price out a head gasket kit and figure $100-$400 to have your head rebuilt. Here I can get the head machined for $100 and lap the valves and service the head while watching TV or listening to the radio. Identify any bad valves and replace, used valves are an option. If the seats are bad, I would farm that out. By pulling the head first, you are only out your time and you will have a fresh top end with all new seals for less than a used engine from a wrecker.

You could also re-ring the pistons by dropping the pan - just do #4 and #5. On my old S80, 2.9 na, I just did one piston ring set and had no issues. Pulling the head is not too bad and will answer many questions if the solvent treatment is ineffective. Once it is off you can decide the course you want to take, being only out time.

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