Hi Guys,

have a 2004 wrx sti

basically the car has been into subaru4you in Newbury and worryingly has given the following compression readings:

1 - 110
2- 125
3 - 105
4 - 85

obviously very concerning low readings, i must say Len at subaru4you was fantastic and full of advice and knowledge, obviously i am going to get the problem sorted but was just wondering if anyone had had similar or low readings before and what the issue was?

so far the main culprits of what it may be are valve seats or piston rings?

thanks

 

I have been thinking of going to get my standard WRX Bugeye 'checked out' including the likes of compression testing. I have CEL on, and commonly over the years it has been the P0303 code. Light flashes when accelerating and changing gears. I once had the Neutral Position Switch changed and problem went away for a couple of years or so, and maybe its the NPS again. I have also been getting some whiffy head gasket smells through heater, but only from time to time and the coolant and oil seems clean and uncontaminated by either. How much did Len charge you for the compression check and was anything else done/checked out?

 

yea , i think len noted a sound difference when turning over and also an idle issue so he done the test anyhow as i was having a major service. results quite worrying to be honest.

 

can someone also maybe tell me if the engine is apart to check said valve seats or piston rings then is it worth changing anything whilst it is all apart? thanks

 

If the valve seats etc are been checked its a engine out job, you might have tight tappets and with this wouldnt need to be done.Also if its had a cam belt changed its possible its not timed right this will also cause the above problem in a ideal world you want readings within 10% of each other and a fair bit higher than what youve got,Was the throttle fully opened when tested as if not you will get low readings,Id check the cam timing first and take it from there

 

I guess readings depends on how it was taken. On my sti it showed 8 bar sharp in 3 cylinders, and 8.3 in one. Tested on a cold engine, my mechanic could only do it like this. I also did this to know where I stand with my engine
I was told that at cold these reading are good, as the most important thing is to have them close to each other. A new engine would have a reading of about 10 bars.
Problem with your readings is that they are not in line, so you will likely look sooner or later to a failure.
If I were you, I'd get the engine stripped and replaced what is needed, as after it fails it would cost you quite a bit more.

 

My guess would be ring land failure on No.4 piston but the compression readings are low across the other cylinders too.

Mick

 

my thoughts exactly, its now booked in to have whatever work needed doing. thanks for the advice guys