Ohhhh Bugger

Gary71 · Post by **Gary71** » Fri Mar 17, 2006 10:23 am

Totally agree with all the others, and I'd get the oil pressure checked on a proper gauge tapped into the sender mounting position rather than trust the instruments. Might give you some piece of mind?

Brendan's car has been making this horrible noise for best part of a year, and we did all consider it about to explode at any minute on last years Northern Event! History has proved us wrong however:lol:

Hope it works out OK

Barry · Post by **Barry** » Fri Mar 17, 2006 1:55 pm

Having just caught up with this thread, Brendan's reminded me of something that happened on mine.

The engine had not long been back together, and had done around 250 miles. For the first time I gave it some beans (demo'ing it to little brother

), when the revs came back down, it was ticking. Sod it, I thought, must be a tappet. crept it home, let it cool overnight.

Checked tappets. Still the same, checked tham again: still the same.

In the end I got right under the car and put my hand up around the head/exchanger joint, and sure enough one joint was leaking. As it happened it was my error as the exhaust hadn't seated.

Point was that it sounded so mechanical that I was considering having to drop the engine. Symptoms (as I remember): what sounded like one really bad tappet that was noticable at idle, worse upto mid-revs, then tailing off at higher revs.

Worth trying the car up on a ramp perhaps?

Like I say, I'd forgotton all about this until Brendan's reminder

.

veryporky · Post by **veryporky** » Fri Mar 17, 2006 3:12 pm

Deffo agree with the others here. Only resort to strip down once you have been down all the other roads. In my experience piston slap tends to occur when the engine is cold due to excessive piston to cylinder wall clearance-wear. Tends to disappear as the motor warms or at least reduce significantly as the clearances tighten. Does it follow that pattern? If not IMO it's unlikely to be piston slap.

Geng's 911T had a similar problem last year turned out to be a problem with a rocker if I remember correctly. It sounded heavier and more serious though. Broken valve spring could sound similar and would show up as low compression.

Personally I would pay for a leak down compression check and checking of oil pressure with an external tester. I would go to another specialist in your area so you also get a second opinion at the same time. Remember to check the oil pressure at 4000 rpm with the motor hot. To get it hot it must be driven for 12 or more miles in these cold conditions to get an accurate reading. Do not trust the specialist to do this as they invariably do not due to time pressures. I speak from personal experience here.

If the compressions come up good and oil pressure is within limits, and the oil consumption is not excessive I would be very reluctant to go for a full strip down just yet. Do those and then post again on here before open cheque book surgery.

Also search on pelican parts. there will be a whole host of listings from people with similar problems. And best of luck......

hot66 · Post by **hot66** » Fri Mar 17, 2006 5:43 pm

Gary71 wrote:

Brendan's car has been making this horrible noise for best part of a year, and we did all consider it about to explode at any minute on last years Northern Event! History has proved us wrong however:lol:

I think we all placed bets on that one

bjmullan · Post by **bjmullan** » Fri Mar 17, 2006 6:59 pm

Hey I had my car out for the first time this year last Saturday. Started after a couple of turns with not major smoke from the back and once she was warmth up I was hitting three figures easy on the motorway.

904GTS · Post by **904GTS** » Fri Mar 17, 2006 8:20 pm

I rebuilt a high mileage 3.2 engine last year which had been randomly making a knocking noise which various people had been unable to diagnose but had no detrimental effect on the running of the engine.

The knocking was being caused by the tensioner idle wheel hitting a web inside the chain housing presumably because the chain had stretched, you can see the grooves that had been machined by the wheel in the picture below. If the leakdown and compressions are OK it may be worth inspecting this area.

sladey · Post by **sladey** » Fri Mar 17, 2006 11:27 pm

THanks a lot for all these suggestions and support.

The car isn't booked in until the 10th April so i'll try nd do some investigation before then - particularly looking for a leak.

It's hard to pick a pattern the fits the noise - it's maybe not so intrusive when cold but I think that's mainlt because the whole thing sounds a bit more clattery when cold. Once it's warmed up sometimes it sounds worse and sometimes it sounds better. When It's bad you can clearly hear it at a distance from the car

Other than the noise it is driving beautifully - better than it has done in a while. Don't know if I can just live with it though - at the back of my mind is the constant thought that it might be getting worse and worse until something bad happens.

Will mention to the garage about carrying out a compression test first - forgive my ignorance though but what will that show? Presumably if compression is down on one cylinder then it points to some sort of leak as opposed to slap.

The idea of a broken valve spring sounds plausible - if that's the case then this should be visible first - I didn't notice anything whne doing the tappets though, but then again I wasn't looking for anything at that stage.

The engine itself was meant to be fully rebuilt in 2002-2003 - crank-case apart etc. I bought it without hearing it run (no choice - blew up previous engine) and apart from a leak caused by a corroded casting which was replaced on installation, it has generally run really well since I had it installed. The problem only occurred shortly after the car had been laid up for 4 months during my backdate project - I'd say the noise started within a week of me driving it.

The guy at the garage comes well recommended - I know Bertroex uses him and he looks after all of Helens cars

Thanks again for all suggestions

Cheers

Mark

g3ngs · Post by **g3ngs** » Thu Mar 23, 2006 2:11 pm

That, as they say, ain't good at all

Lightweight_911 · Post by **Lightweight_911** » Thu Mar 23, 2006 2:27 pm

Piston slap is due to excessive clearance between the pistons & cylinders...

Nige · Post by **Nige** » Thu Mar 23, 2006 2:45 pm

Lightweight_911 wrote:Piston slap is due to excessive clearance between the pistons & cylinders...

that's what I thought, shows itself under load, my first car, a 1964 Vauxhall Victor had more slap than Barbara Cartland. The piston was like throwing a sausage down a jitty.

sladey · Post by **sladey** » Thu Mar 23, 2006 5:03 pm

Thanks for all that - I thought piston slap was the top of the piston hitting the valve(s) - which shows what I know!

g3ngs posting was really helpful - my symptoms seem to match the second thing very closely - it's drowned out at higher revs. Also aside from cozy powell in the back the engine has been running very sweetly - I've had the car back now since January and it's still performing really well. The noise has been there all this time - I think it's getting worse but it's hard to tell - some days it sounds worse than others - you can definately tune your ear in and out of it

If it is a new camshaft anyone know how where and how I'd get one?

Cheers

Mark

sladey · Post by **sladey** » Thu Mar 23, 2006 5:05 pm

Actually following on from that an re-reading the post I've had piston slap before if that's what it is - on my previous engine (that says it all really)

Machine gun went off in the back whilst overtaking my brother - towed it to Merlin who said it needed full bottom end rebuild, bought new engine (3 years ago)

Mark

baggy_aggy · Post by **baggy_aggy** » Thu Mar 23, 2006 5:33 pm

Just to make you all think, I booked my 1970 T (Conrad's old car) in at GCS to make sure the value clerences were ok (tad harder to sort than the flat4) as things just felt hot, thought there was an odd noise as well. Anyway I got a call asking to go back and have a listen to what they had found, (a part from a strecthed timing chain) there was a definately grumble/metalic knocking from within the case. Jez unfortunately knew exactly what it was. There are two shell bearing that the shaft that drives the oil pump sits in (might not be the best description but you known where I mean). Well sometimes these can be put in back to front, so engine out, stripped and .... during it's last rebuilt the bearings that were used were 993 ones, too small hence moving within the case, hence grubling etc. On the upside, I knew the car looked straight and drove great now I know the engine is bang on. Oh and another cause of the rev counter going all over the shop is the shaft in the distributor not having enough copper slip. I'd recommend GCS by the way.

g3ngs · Post by **g3ngs** » Thu Apr 06, 2006 10:26 am

Just when you think there's nothing left to throw money at, typical

sladey · Post by **sladey** » Thu Apr 13, 2006 11:40 am

Just to give an update on this,

My car went into Zentrum on Monday. Monday they took the engine out, Tuesday they stripped down the side of the engine that was giving the noise. No piston slap - all pistons look OK. Their only issue was that the bores hadn't been honed very well.

Moving the con-rods from side to side pointed at the problem though - number 6 conrod had more lateral movement than the other two. As I wiggled it I was getting a noise very similar to what iv'e been listening to over the last 3 months - the fact that It was on number 6 would point towards the noise appearing on the right hand side of the engine.

This pointed towards the big end bearing having worn.

Yesterday they stripped the other half of the engine and split the case. When they got it all apart they found that 3 of the big end bearings had scoring. They said they don't have technical spec for the size of the big end bearing so can't check it against spec, but they clearly look damaged.

The good news was that the rest of the engine looked really good - no problems and it all came apart easily. There have been oil leaks on the engine which will be cured when it's put back together again, and also one chain tensioner was incorrectly installed leading to some chafing - that will be replaced.

Now, do I go for the 3.4 barrel & piston set

Mark