Quote:
Originally Posted by Chris1Roll
It was only raining a little bit this morning, and my compression tester (I wouldn't save it was especially expensive -it cost £40 rather than £15 - but the braided hose still spun in the fitting and I had to uses some pliers to remove it from the engine.. I wouldn't want to thread it into a twin cam engine.) and new feeler gauges had arrived yesterday, so I set about my investigations.
First I started the car up and ran it up to temperature at idle - It was a little lumpy when cold - then shut it off and removed all the spark plugs.
Removed fuses 1 and 11 (Main pump/ignition and in-tank pump), hooked the battery up to the C70 on some jump leads to make sure that was consistent, screwed the tester into No1 cylinder, held the throttle wide open and turned the key.
Nothing.
After a few moments of confusion, and checking which fuses I had removed, I put the gearshift back into P and tried again - at least I know the interlock works now.
Try again, throttle wide open, and cranked until the reading stabilised
No1 - 170
No2 - 195
No3 - 155-170 (was inconsistent over a few attempts)
No4 - 195
I'd have been happy with 170 across all, but apparently it can achieve 195 (which seems high to be honest, but the engine does only have 82k on it?)
I did each cylinder in turn again to be sure (and a few more on number three) with the same results.
13% lower on 1 and sometimes more on 3; I don't think that is quite what I was hoping for.
Then it started to rain so I went and hid in the shed for a bit while deciding to carry on and check the valve clearances.
By the time I got to this the engine had been cooling off for probably 3 hours. I can do it again one evening so it's definitely cold but really its the differences I'm looking at. (my gauges only go up in 0.05 increments, I should have checked that when ordering..)
1E 0.35
1I 0.5
2E 0.4
2I 0.45
3E 0.35
3I 0.5
4E 0.35
4I 0.45
Is the fact that the inlet valve clearances are bigger and out of tolerance even for a warm engine let alone cold, on the same cylinders that have the lower compression of any significance, given that the inlet valves are larger and in theory more likely to get tweaked by the dome on the top of the B200e pistons? |
Well done.
I wouldn't worry too much about the 195 PSI readings being higher than you expected for an 80,000 mile engine; your expensive (in my terms, but then I'm a tightwad) tester hasn't particularly been calibrated against anything. The important thing is the difference between the cylinders - having them all within 10% is a good thing.
The first, simplest and cheapest thing to do is a wet CR test (as Dave suggested above). The pressure will increase a bit anyway (just due to the volume of the oil - I normally use a squirt of ATF); if the increase is significant for cylinders #1 and #3 (but less so for #2 and #4) that would indicate the a bottom end issue (rings or bores). If it doesn't make so much difference then top end: HG or valves.
If it turns out to be likely a bottom end issue then it would be a good idea to have a look with an endoscope. I bought a really cheap (about a tenner) one that plugs into an old Linx 7 windows tablet that I keep just for oily jobs. I find it perfectly good for reconnaissance tasks like this one, so I'd suggest you don't take so much notice of reviews (which will be mostly written by IT buffs rather than someone wanting a quick look inside a cylinder head).
If the wet and dry CR test indicates it is a top end issue then the only real way of checking is to remove the head, but that only takes an hour or so. Getting it tested and skimmed probably isn't something you will be able to do yourself, but it is pretty standard engineering and you should be able to find someone to do it locally. If you do that it would be a good idea to adjust the valve clearances and then fit new hushers before putting it back on the motor car.
If you do take the head off it is easy to inspect the bores then. If they aren't scored then it might be okay to just hone the bores and fit new piston rings. I did that on the RB (I'll find a link for you and post it below before going Bobwalkin) with entirely positive results. It is a job you could do yourself at home in about a day.
I think someone said above that it was necessary to remove the hushers before checking the valve clearances. That isn't so with an 80,000 mile engine: rubber husters that old will have no effect on the clearances. It is only important to check the the clearances without the hushers when they are brand new. Someone else said that it is necessary to remove the cam to change the hushers - that isn't so either - if you use a valve shim remover tool (I think I posted a photo of mine somewhere above) then you can take out the shims one at a time with a magnet and use some long tweezers to swap the hushers. If you do take the head off for checking, then it is easier to set up the valve shims with it on the bench, but I'd still use a valve shim remover tool to insert the hushers one by one so as not to disturb the cam again.
So, I'd suggest the first thing to do is a free and easy wet test, then maybe a look with a borrowed endoscope (or buy a cheap one from eBay) - and then decide what to do about it (if anything). You may be over-thinking this a bit - I doubt that a valve is bent - the difference is CRs is probably due to fair wear and tear on a 30 year old motor. If you bought the motor car fairly cheaply and it runs okay now I'd probably suggest just screwing it back together with a new tensioner, adjusted valve shims, new hushers and and then just keeping an eye on it (that is probably what I would do). If on the other hand you want it to be perfect then work out which of the remedial jobs need doing. It just depends on how good you want the product to be, and how much effort you want to spend on getting there).
This is the beauty of running an older motor car - to me it sounds like a marvellous project
.
Good fortune,
Alan
Addendum: Here is the link to the bore hone/piston rings work I did on the RB. It wasn't that difficult and if I remember correctly took about two days (spread over 4 days) - but that included lots of tidying up jobs:
https://www.volvoforums.org.uk/showp...postcount=2915
... I did notice that oil consumption was high for about 100 miles after the job, but that soon settled down.
