Evening, I bought a 05 Impreza WRX 5/6 months ago and had a compression leak test done as a general health check.

Cylinder 1-3 were fine but cylinder 4 measured at 12% compression leak.

I don't drive the car hard often and it's pretty much standard power, I've no ambition to push for big power either.

What would people do? Wait for it to eventually go and take the hit of a rebuild or should I be stopping using it and having it repaired, what can even be done about this and what are the costs like nowadays? I've no plan on selling this car, I don't need the cash out of it and have always wanted one so if it did eventually blow it would be garaged until I decide what can be done.

Thanks,

 

Depends what the cause is. It could be valve stem seals, piston rings, head gasket etc. What were the compression numbers across the cylinders?

 

Results as follows:

Compression test
Cylinder 1 - 9.8
Cylinder 2 - 9.8
Cylinder 3 - 9.7
Cylinder 4 - 9.6

Compression leak test:
Cylinder 1 - 8%
Cylinder 2 - 8%
Cylinder 3 - 6%
Cylinder 4 - 13%

It was said he couldn't hear the air escape through the exhaust and there was no bubbling in the coolant etc, he said it points towards a bottom end issue.

 

On a 2.0l presumably?

 

Yes 2.0L

 

I'd probably just drive it until if fails, if not able to identify exactly the issue and fix myself.

What's the mileage? Any mods?

 

I have no mechanical knowledge so all work being done is via a mechanic, no DIY jobs on my drive sadly!

Ticked over to 136k yesterday, mods are:

- Aftermarket downpipe with a sports cat (or so I'm told by the mechanic, this was done before me)
- Jap speed cat back
- GFB dump valve
- Air induction intake with a cone filter hidden in the front/side bumper section

 

Mods but no remap?

 

Correct, the chap said a map wouldn't necessarily be required if you aren't going for higher power because, he said the air intake is before the MAF and still measures air correctly coming in, the bolt on exhaust system wouldn't cause harm.

He said at worse if you set the dump valve to recirc some it will impact performance as it's unmeasured air being taken back in and would need mapping to be safe but the dump valve is set to fully VTA

 

Is the "chap" your mechanic or the previous owner? Please let it not be your mechanic. You can't reliably run both an increased air intake and outlet on a high mileage turbo impreza without eventually meeting with pain.
But it sounds like that horse has already bolted, so I would agree with the above advice and carry on til it fails, whilst budgeting for a rebuild, or get it investigated if money isn't an issue

 

Appreciate the replies.
What are rough costs of rebuilds if the bottom end goes? Is this a better option than buying a new engine from a breaker as you never know the condition underneath until its taken apart, often too late at that point!

Like I said earlier, I don't mind the money tied up in it and I've no plans on selling. If the government are going to force us into electric vehicles I'm keeping this till they tow it away!

Also, do I forge for additional reliability, how much extra is that in todays market? I don't want big numbers, I don't race and I've never done a track day (unlikely I ever will). It sees occasional pulls but majority of the time never sees above 3k RPM. I like the sounds of it, and love the look of it.

The chap is a jap specialist and engine builder. He already knew of the compression leak in C4 as he'd done that test prior to adding the dump valve and induction inlet and told me of the findings. His advice was as above, save money aside and compression test every 12 months, if its getting no worse happy days if its increasing 1 or 2% per year then its on its way out.

His points made sense however, if the MAF is reading air inflow correctly, why would the ECU need altering? And surely the dump valve makes no difference to the way the car runs, don't they have stock dump valves on anyway to remove the extra air between the throttle plate and the turbo once the plate shuts? I'm no mechanic by any stretch however...