Higher compression in one cylinder?

[dcuk 0]

Hi,

 

Ive just done a compression test on each of the four cylinders on my C, First ones fine, showing 13 Bar which is good as Haynes manual states its the pressure of a "New" engine, cylinders 3 and 4 are pretty much the same, 4 showing 13.5

 

The problem is that cylinder 2 is showing 14 Bar which is too high. Just wanted to know what this means? Am i right in thinking these results mean theres nothing wrong with the piston rings and its something to do with the head, and if so what are the common causes?

 

Engines a 16v Kr and a bit smokey after its warmed up and given a few hard revs. Other than the smoke it idles and drives beautifully, even though it consumes a lil oil and leaks a bit.

Its done 185,000 miles and theres no evidence in the history to say its had a rebuild or head work done on it.

 

Cheers!

:)

[andy 0]

I wouldn't worry in the slightest personally. 13 bar may well be a typical average value for compression on a standard engine. That doesn't mean some engines aren't made to tighter tolerances and that higher values can't be encountered. I expect they all started at 14 and the rest have dropped a bit with time as is normal. You could argue that 3 out of four of yours are too high going on what Haynes say, no chance!

[dcuk 0]

Cheers for that!

 

Thats what i thought, the readings sound quite healthy to me which was a relief, i was expecting them to be real lowww... but the thing is, ive heard that high readings could mean a problem with valves sticking or something similar(ive never really had a go at cylinder heads, so forgive me for sounding clueless)

 

Assuming alls good then, what could be the reason for the blue smoke? I also noticed the plugs are all sooty n black which indicates its running rich right?

[andy 0]

Smoke could mean worn piston rings, it doesn't sound like it in your case. It could also mean worn valve stem seals, does the car smoke all the time or worse after standing, worse on the overrun etc? What colour is the smoke too....blue or white?

[dcuk 0]

Well, its blue smoke, its fine until given a good few hard boots on the throttle and also on the overun.

 

The head sounds quite rough and noisy too, not very smooth... like the cam chain isnt right?

[dr_mat 0]

You might want to do a leak down test aswell. Piston rings can form temporary seals (enough for a straight compression test) even when well worn.

[a_riot 0]

I would think that carbon buildup somewhere in the combustion chamber will cause an increase in compression. I don't think it takes a lot of buildup to make a difference. Only thing is that if that were the case you would think you would be hearing some predetonation first.

Paul

[dcuk 0]

a_riot - Ive been thinking it could be carbon build up too. As i said earlier, the spark plugs are really black. Assuming it is just carbon build up, could it be down to a problem with the head?

 

Im seriously considering taking the head off and havin a a go at doing the valve seals/stems and timing chain as it is quite noisy.

[dr_mat 0]

carbon build up can be caused by injector issues, iirc.

Does the car seem to be using too much fuel?

[**stan** 0]

The smoke definately sounds like a stem seal issue to me. These can be changed on an 8 valve with the head in place. Not so sure about a 16v though.

[dcuk 0]

dr_mat - The fuel consumption is fine, quite good actually.

 

Cheers Stan... I think im just gonna go for it and take the head off.

[davidwort 0]

dr_mat - The fuel consumption is fine, quite good actually.

 

Cheers Stan... I think im just gonna go for it and take the head off.

 

I personally would leave well alone if the engine runs nicely, most valvers burn a bit of oil, in fact that doesn't do any harm at all.

Providing it passes the emissions, which are not that stringent on a KR, then I'd wait until it really needs work doing.

If you are dubious about the timing chain, then take the cam cover off and have a look, they tend to last pretty well as they are constantly running in oil.

Bear in mind that you will be looking at shelling out for:

 

a timing chain

head gasket and bolts

inlet manifoild gaskets

exhaust gaskets (studs and nuts)

stem seals

cam cover gasket

coolant change

 

and possibly:

injector seals

cam belt and tensionner

oil change

anything else you damage (or looks to old not to replace) when taking the head off

spline tool set

torque wrench

 

that soon adds up.

 

Also, it may be hardened stem seals, but more likely worn guides, in which case your oil burning will just come straight back if they're not done.

[dcuk 0]

Yeah i see your point about the bits adding up and costing a few quid. Might just take the cover off and have a look at the chain like you said.

 

Whats best the best thing to clear the carbon build-up without takin it apart? Redex claims to do this, but does it really work??

[Louie Lungbubble 0]

My motor's the same as dcuk's at the min. I've been told it's just as likeley to be worn valve guides letting the oil through as the stem seals .

 

What's involved with sorting the guides... Machine shop jobbie to have them re-sleeved, is it?

[davidwort 0]

My motor's the same as dcuk's at the min. I've been told it's just as likeley to be worn valve guides letting the oil through as the stem seals .

 

What's involved with sorting the guides... Machine shop jobbie to have them re-sleeved, is it?

 

yep, head off new guides pressed in, and there's quite a few of them, you might be lucky and only need the exhaust ones done though.

 

I wouldn't attempt to clean the engine out with Redex etc... you might cause more trouble than leaving it alone, regular oil changes and a good thrashing is best for the valver :) - 'Italian tune up'

[h100vw 0]

Valve guides on KR are not at their best after 100K. Unless you are going to do it all your self except for the guides you are looking at £100 to 150 quid to get started.

 

If I were to be going down this road I'd consider getting another head prepared in advance. Then it would just be a swap over and the car would be off the road for less time.

 

You still need to be prepared to shell out on an oil change, gasket kit, coolant flanges, damaged knuckles, tools etc.

 

150 quid buys a lot of oil or even another engine 8)

 

Gavin