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Topic: Lack of compression - valve removal (Read 1856 times) |
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Mike_Floutier
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'97 2.3 Ultima saloon lpg
 
Posts: 296
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Lack of compression - valve removal
« on: Aug 10th, 2008, 5:08pm » |
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Ok, I've got low-pressure in my back cylinder (6 bar compared to 13 in the others) - I noticed this after my radiator blew out the other night.
Having got my head gasket off (with much help) and finding this looking ok and the head flat I noticed this "black valve" see - http://www.exhortations.co.uk/images/The%20valves%20top%20is%20front%20c yl.jpg.
Do you think this may be the cause of the low compression? If so, does anyone have any actual experience of removing a valve on the car (as the Ford diagram shows far to many special tools).
Dave suggested pouring paraffin onto the valves to see if the "black" valve was less "tight" that the other cylinders. I used meths instead as I don't have any paraffin; would this matter?
Anyway I do want to get to the bottom of the lack of compression before reassembling the head.
btw does anyone know what a blown head gasket looks like? This is a pic of mine (at the offending cylinder) but I don't really know what to look for http://www.exhortations.co.uk/images/Head%20gasket%20low%20compression%2 0cylinder.jpg.
Thanks
Mike
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Snoopy
Administrator
Very old.BAD tempered and missing friends.
Posts: 6278
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Re: Lack of compression - valve removal
« Reply #1 on: Aug 10th, 2008, 5:40pm » |
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If its BLACK sooty type and quite a thick build up then it suggests to me oil burning with combustion and that would suggest rings, its its the hard type of carbon then more likely petrol/oil and that would be valve seals . Valves are NOT too hard to get off with spring compressor just mind the collets though. if it is valves then reseating and gringing in should do the trick along with perhaps new guides!
A good all round tool box and some valve spring compresor you should be able to manage .
GOOD LUCK
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bizzay1
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1997 Cosworth Saloon
Posts: 481
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Re: Lack of compression - valve removal
« Reply #2 on: Aug 10th, 2008, 5:43pm » |
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I would say that there was nothing wrong with the head gasket, normally from what I have seen, if the gasket is blown there are black trace marks either between cylinders (and pressure from both would be down) or black/water marks between cylinder & water ways(& would give water loss/overheating problems) that valve does look as though it has got very hot, can you force the valve open with something to see if the seat is burnt ??
just seen snoopys reply - surely if it was rings it would be all valves blackened ??
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Mike_Floutier
Full Member
'97 2.3 Ultima saloon lpg
Posts: 296
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Re: Lack of compression - valve removal
« Reply #3 on: Aug 10th, 2008, 6:21pm » |
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Good deductive point about "just one valve". I had a good look at it, without compressing it, and the black carbon flakes off pretty easily. It is still pretty black compared to all the others which are this "light, brick dusty" colour.
Assuming I can pick up a spring compressor tomorrow, having compressed the spring, how do you go about getting the valve out and cleaning it? I've not done this before.
Mike
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bizzay1
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1997 Cosworth Saloon
Posts: 481
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Re: Lack of compression - valve removal
« Reply #4 on: Aug 10th, 2008, 6:31pm » |
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If they still use the same method as when I was a lad - once the spring is compressed you will see 2 collets which fit in grooves at the top of the valve stem, these should just come off in your hand so to speak, release the spring tension and the valve will pull out
ohh and it's not just cleaning it, it's lapping it in using an abrasive compound so both the meeting faces, when together, give a gas tight seal
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Mike_Floutier
Full Member
'97 2.3 Ultima saloon lpg
Posts: 296
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Re: Lack of compression - valve removal
« Reply #5 on: Aug 10th, 2008, 6:37pm » |
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How do you do that lapping thing? I remember doing something like that on my old motorbike many, many years ago but I think there was a slot for a screwdriver so you could turn the valve to grind it. But these have no slots so how do you turn them I wonder?
Mike
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Mike_Floutier
Full Member
'97 2.3 Ultima saloon lpg
Posts: 296
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Re: Lack of compression - valve removal
« Reply #7 on: Aug 10th, 2008, 10:05pm » |
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Thanks Bizzay, that's really helpful, my challenge will be to get a suitable compressor to deal with the angled, recessed springs.
I deduce from the procedure for "valve stem seal replacement" http://www.fordscorpio.co.uk/manual/engines/dohc2_3/2300ValveSeals.pdf on the site and comments in your "mini" instructions that this must be a common problem.
I'm guessing that what's happened in my case is that the seal has worn out on my "black" valve leading to the oil in the camshaft box (being under pressure) being forced onto that exhaust valve.
I'm also assuming that this leads to the formation of the carbon deposits that we see on the valve and also deposits and maybe wear on the valve mating surfaces which has presumably caused my poor compression (6 bar).
Does this make sense?
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bizzay1
Full Member
1997 Cosworth Saloon
Posts: 481
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Re: Lack of compression - valve removal
« Reply #8 on: Aug 10th, 2008, 10:22pm » |
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Was never quite that complex in my day Mike - we had points and condensers and things, - and you could get at the valve stem seals with your fingers 
By reading your guess it all seems quite possible
best of luck with the rest of the job
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Mike_Floutier
Full Member
'97 2.3 Ultima saloon lpg
Posts: 296
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Re: Lack of compression - valve removal
« Reply #9 on: Aug 10th, 2008, 10:31pm » |
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Thanks! Will let you know how it goes.
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gozz
Senior Member
Been around awhile
Posts: 3475
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Re: Lack of compression - valve removal
« Reply #10 on: Aug 10th, 2008, 10:46pm » |
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bizzay.
Snoopy thinks that you could have busted rings on one cylinder I think.Did'nt you do a compression test with oil down your bad bore ? this is how you check for bad piston sealing.Put some paraffin or diesel into your bad cylinder and also into a good cylinder,compare the length of drainage time,you may need to leave it overnight,Best not to use meths for this as it is rather volatile to have in the sump.
Just something else for you to do!
GOZZ.
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bizzay1
Full Member
1997 Cosworth Saloon
Posts: 481
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Re: Lack of compression - valve removal
« Reply #11 on: Aug 10th, 2008, 11:11pm » |
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Gozz - it's not me that has the problem - it's Mike, the reason I questioned snoopys suggestion of rings was the picture that mike has a link to - of the four valves in the cylinder in question only one is blackened and looks as if it has got hot, Mike did a test and had 6 bar in that cylinder - the other 3 had 13 bar, hope this clarifies things
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Mike_Floutier
Full Member
'97 2.3 Ultima saloon lpg
Posts: 296
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Re: Lack of compression - valve removal
« Reply #12 on: Aug 11th, 2008, 7:00am » |
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Bizzay1 is accurate on all counts.
However your point Gozz about waiting all night for the paraffin (when I get some instead of the meths) is well met, I had poured onto the valves and expected it to drain away instantly.
I'm going for the burnt "black" valve having a failed oil seal, my main challenge (apart from getting parts) is to get a suitable spring compressor for the recessed, angled spring.
My other challenge is that I need to change the seal and get everything back together and the car running (not to mention the new radiator) by tonight ready for work tomorrow.
Any tips for compressing Scorpio springs would be appreciated.
Thanks
Mike
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gozz
Senior Member
Been around awhile
Posts: 3475
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Re: Lack of compression - valve removal
« Reply #13 on: Aug 11th, 2008, 8:42am » |
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Mike and Bizzay.
Sorry about the confusion,senility is setting in.Mike I have'nt done much on that engine,but most overhead camshaft heads use a spring compressor with a piece protruding downwards onto the spring cap as against a normal OHV which does'nt.
I have both types,but suppose that's no use to you.You can of course buy one from a tool shop or even Halfords.More expense !
GOZZ.
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pete from Hull
Senior Member
Non Scorpio at the moment, but still interested...
Posts: 1365
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Re: Lack of compression - valve removal
« Reply #14 on: Aug 11th, 2008, 8:46am » |
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on Aug 11th, 2008, 7:00am, Mike_Floutier wrote:
Any tips for compressing Scorpio springs would be appreciated.
Thanks
Mike |
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Poor mans intuition..... 
Make a cast of the combustion chamber, ie: line it with clingfilm and pour in plaster/ plaster of paris or polyfiller and leave to set. This gives you a suitable plug to press against.
Put tissue into the combustion chamber and insert the plug, put a board on the head and turn it over. Then using a pair of pliers you can compress the valvespring and remove the collets.... Job done.
This is the way I have carried out this task in similar circumstances in the past.
I hope this helps.
Pete
PS I have a spare cylinder head for sale.... Plug Plug...
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Tompion
Administrator
1997 2.3 Ultima estate.
Posts: 2918
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Re: Lack of compression - valve removal
« Reply #15 on: Aug 11th, 2008, 9:38am » |
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Mike
A failed valve seal won’t cause lack of compression.
On your picture the valve looks blue rather than black/oily as though it’s got to hot.
The valve dissipates heat via the seat, if the valve’s burnt or pitted or bent then it doesn’t get rid of the heat quick enough, (don’t know but possibly more of problem on gas).
You may need to get the seat recut if it's bad.
Dave
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bizzay1
Full Member
1997 Cosworth Saloon
Posts: 481
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Re: Lack of compression - valve removal
« Reply #16 on: Aug 11th, 2008, 10:00am » |
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Thats what I was getting at earlier Dave, when I asked if he could compress the valve spring to have a look at the seat, but while he's at it just as well replace the seal
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Mike_Floutier
Full Member
'97 2.3 Ultima saloon lpg
Posts: 296
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Re: Lack of compression - valve removal
« Reply #17 on: Aug 11th, 2008, 10:23am » |
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Ok, thanks guys,
I'm back from All-Parts and Fords loaded with goodies:
1. Spring compressor for recessed springs,
2. Hydraulic chain tensioner plunger,
3. New spark plug
4. Valve grinder & paste
5. Coolant
6. Valve oil seals
and I've got on order for this afternoon:
1. Head bolts
2. Radiator
3. Cam shaft follower - for the "black" valve - it's not actually blue, that's the camera or the printer, it's actually black carbon that you can scrape of if you try.
4.Cam-chain top guide - which I broke getting it off
Right, to work, will let you know how it goes.
THanks again!
Mike
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Mike_Floutier
Full Member
'97 2.3 Ultima saloon lpg
Posts: 296
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Re: Lack of compression - valve removal
« Reply #19 on: Aug 11th, 2008, 11:05am » |
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Ok, how do you get the old oil seal off?
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