Not a happy car

Gp79

Member
Messages
1,393
When I first got my GS i found one of plugs loose and all full of oil.

This did not affect the running though, hope it solves your problem.

It took about two evenings to do both rocker cover gasket sets going steady.
 
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spn

Junior Member
Messages
88
Your rocker seals probably need doing but if you have high crank case pressure, it'll force more oil out. Probably worth doing the compression test and ideally a leakdown test before you replace the seals because if it's a piston, ring or head issue, the covers will have to come off again.

Good luck,

Simon
 

alfatwo

Member
Messages
5,517
Your rocker seals probably need doing but if you have high crank case pressure, it'll force more oil out. Probably worth doing the compression test and ideally a leakdown test before you replace the seals because if it's a piston, ring or head issue, the covers will have to come off again.

Good luck,

Simon

And engine out and strip!

Dave
 

CatmanV2

Member
Messages
48,539
Your rocker seals probably need doing but if you have high crank case pressure, it'll force more oil out. Probably worth doing the compression test and ideally a leakdown test before you replace the seals because if it's a piston, ring or head issue, the covers will have to come off again.

Good luck,

Simon

Would high crankcase pressure increase pressure under the rocker covers? I was under the impression that the entire crankcase was sealed by the heads and the head gaskets?

C
 

Zep

Moderator
Messages
9,110
Would high crankcase pressure increase pressure under the rocker covers? I was under the impression that the entire crankcase was sealed by the heads and the head gaskets?

C

Yes, the oil supplied to the cam bearings (and the crank bearings for that matter) flows out of the ends of these journals and drains back from the top of the heads into the sump pan to go back to scavenge part of the pump. If there is excessive pressure it will find its way back up these drainage galleries.
 

jasst

Member
Messages
2,313
New compression tester has arrived, but never having done it before, would be grateful of some advice re the correct procedure, get various answers from google, so 1st, should the engine be warmed up first, or is it ok to do it from cold?, 2nd, obviously all plug leads and plugs removed, but is there any thing else to disconnect electrically? any other tips very much appreciated.
 

Gp79

Member
Messages
1,393
If you have already got the plugs out I would just use it.
Make sure the coils can’t go to ground incase they get damage them.

Ideally you would want to have had the engine just run so the rings are sealed better etc
Just give it a good crank and look for each cylinder to give similar pressure to each other.
 

alfatwo

Member
Messages
5,517
And if possible have the engine on full throttle openings, as the cylinders won't have as much air filling if it's on idle mode

Dave
 

Zep

Moderator
Messages
9,110
As Dave says, you need a WOT (you could remove the throttle body to save messing about) and you should pull the fuse for the fuel pumps so you don't fill the bores with fuel.
 

jasst

Member
Messages
2,313
Right, compression test just done, after the hastle of getting one that would actually fit, and results are
cyl 1 140 psi
cyl 2 150 psi
cyl 3 155 psi
cyl 4 150 psi
cyl 5 145 psi
cyl 6 150 psi
cyl 7 145 psi
cyl 8 145 psi

to my mind these figures seem to be within acceptable tolerances, unless of course you know different!!!
 

allandwf

Member
Messages
10,958
The spread seems reasonable, but are they not all quite low? I would have thought high hundreds at least. I'm sure someone will be along who knows the correct figure.
 

Lozzer

Member
Messages
2,280
The spread seems reasonable, but are they not all quite low? I would have thought high hundreds at least. I'm sure someone will be along who knows the correct figure.

That disappointment you get when you see "The spread seems" on the main menu, only to find its all about compression ratios............:p
 
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mjheathcote

Centenary Club
Messages
9,033
Right, compression test just done, after the hastle of getting one that would actually fit, and results are
cyl 1 140 psi
cyl 2 150 psi
cyl 3 155 psi
cyl 4 150 psi
cyl 5 145 psi
cyl 6 150 psi
cyl 7 145 psi
cyl 8 145 psi

to my mind these figures seem to be within acceptable tolerances, unless of course you know different!!!

They look the same as my V8 Triumph Stag figures done cold, so look okay to me!
 

jasst

Member
Messages
2,313
Have spoken to Dan the Maserati technician from Ftech, and he says the figures are ok, so that is a weight off my mind, still to fathom out what the problem is though.
 

Zep

Moderator
Messages
9,110
Great news on this front at least. Were you able to do a leak down?

I would now def try running it with the breather pipe disconnected from the inlet and into a bottle. If there is no smoke that totally rules out the bottom and and valve seals.
 

jasst

Member
Messages
2,313
No, haven't done a leak down as don't have the equipment or knowledge, have now totally removed the exhaust to check for obstructions (what a ball ache that was, as only have car ramps to get the back of the car off the ground) and needless to say there was no sign of any obstruction. Before I removed exhaust I removed the two breather pipes from the oil reservoir and ran car on tick over, the large pipe from oil tank to inlet pipe I could feel nothing, the smaller of the two pipes, which come from the cam covers I could feel suction. When exhaust is back on going to get a friend to come over and do some exploring while revving it up to see what happens, is very difficult to do these things when you are on your own.

Edit:- just googled all about leak down testing, doesn't look that complicated, guess I'd better find a leak down tester from somewhere. ( yet more tools, going to need a bigger garage just to store them soon! )
 
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RobinL

Member
Messages
456
I really wouldn't worry about a leak down test. A leak down test with the piston at around bottom on firing stroke will test the cylinder / bore / piston and valve sealing. Following this you might do a compression test which dynamically adds in test for valve sealing. Cold leak down is something I would do on an engine I didn't want to spin up just to get a heads up. So you won't learn anything extra (in my opinion)
As you already have pretty reasonable compression test readings - for an 11:1 compression ratio upper number would be 160's and acceptable down to 145. Variation is less than 10% so all good. 1 is marginal but, again in my opinion, an indication of wear and not a problem/fault indication. A 'hot test' may just show it has bedded in differently.
 

Zep

Moderator
Messages
9,110
I really wouldn't worry about a leak down test. A leak down test with the piston at around bottom on firing stroke will test the cylinder / bore / piston and valve sealing. Following this you might do a compression test which dynamically adds in test for valve sealing. Cold leak down is something I would do on an engine I didn't want to spin up just to get a heads up. So you won't learn anything extra (in my opinion)
As you already have pretty reasonable compression test readings - for an 11:1 compression ratio upper number would be 160's and acceptable down to 145. Variation is less than 10% so all good. 1 is marginal but, again in my opinion, an indication of wear and not a problem/fault indication. A 'hot test' may just show it has bedded in differently.

I see your point, but leak down can help identify leakage paths too. Here we think that something is pressurising the crankcase. With a leak down test it will put more pressure into the system than a low speed crank of the compression test. This way if there is more blow by on one cylinder, this will be evident from air passing out of the breather. Ditto if it is the head gasket with a breach into an oil way. In short it is a method of creating running pressure in the cylinders without having to start the engine. I admit I would probably run it with the breather connection to the inlet disconnected and see what is coming out.