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Nasty noise from a 3.9 V8


Andrew Cleland

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I posted a short version of this in the Megasquirt forum, but seeing as it's more of a mechanical thing than a fuel injection thing, I thought I'd throw it in here as well...

I've just fitted a Thor manifold onto my 3.9 V8 - not too tricky but a few gotcha's, which I'll write-up as a 'how-to' for the forum one of these days. As well as the actual manifold I also fitted the Thor injectors and fuel-rail (as the Lucas one doesn't fit) and now have the fuel pressure in the rail controlled by an external Aeromotive unit. The engine is mechanically fairly standard, although the cam is a Crower 50229 and it has Rhode's lifters. It's been running for around 6 months with this cam and the lifters without any problems or nasty noises (in-fact much quieter than I was expecting for Rhode's lifters).

This morning I started the engine for the first-time with the new manifold - fired-up fairly OK, although the Megasquirt will need tweaking as the Thor injectors flow more than the old Lucas ones, so the idle needs a bit of a help with the accelerator pedal, especially as the engine's cold. The problem though is a very nasty knocking sound coming from the engine:

It seems to be coming from the valley area, which makes me suspect a stuck lifter. I've given the engine a few minutes at a gentle idle to see if it would go, but my mechanical sympathies eventually won out and I stopped the engine, as it's a nasty noise. I've also used the oil pump priming tool in a drill to give it a few minutes of oil at pressure (around 2,000rpm on the drill) to see if that would cure it. No luck :(

So, I'm resigned to having to pull the manifold off again to get into the cam and see what's what, but before I do (and it's a PITA to do), does anyone have any thoughts on what could be causing this noise?

Cheers,

Andy.

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Christ that sounds dreadfull :lol:

Check you have opil pressure !!!

Nige

Well, the oil pressure light goes out on start-up, so I guess so - "dinky dizzy" must be doing it's job. I did check the dipstick and it was looking a tad low, but that was just after my efforts with the priming tool, so I figured some oil was probably still hanging around in the galleries and the Vee, so it would read a tad low. I plan to check the level again tomorrow morning after we've both had a night's rest!

Andy.

p.s. Have some photos of my bodge modification to fit the EDIS coilpack bracket to the Thor manifold which I'll send through to you.

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I once had one of my Landcruisers come back to the yard with that sort of noise...It was a broken piston (Skirt was broken but not through the gudgeon)the driver drove about 50klm like that...bloody idiot!!! luckily we were able to take the head off and hone the cylinder and fit a new piston and rings....very very lucky.

Good luck mate.

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I once had one of my Landcruisers come back to the yard with that sort of noise...It was a broken piston (Skirt was broken but not through the gudgeon)the driver drove about 50klm like that...bloody idiot!!! luckily we were able to take the head off and hone the cylinder and fit a new piston and rings....very very lucky.

Good luck mate.

Hopefully not that! The engine was fine and hasn't had anything done to it that could cause that, so finger's crossed!

Anyhow, it's 7:30, not raining and there's daylight outside, so I'm going to crack-on with opening up the engine and seeing what I can see...

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to me that sounds too fast to be cam related, sounds piston / little-end-ey to me . does it get better / worse under load? sound any different if HT leads disconnected one at a time?

I think you're right. I started by getting into the cam valley today and all looked fine, lifters all ok and the pushrods all tight. Then I pulled the plugs and turned her over on the starter - the noise was still there but seemed to be coming from deeper inside the engine (and was a deeper thonk at starter speed and without the engine firing). Next step was to drop the sump and have a butchers - all looked fine, no bits of metal in the oil and I checked the torque on the mains and the big-ends and all was fine. What I could see of the underside of the pistons looked OK, but it's hard to see much from down there.

I put the sump back,fed it fresh oil, checked the oil pump pressure with the priming tool in the drill and got plenty of oil flowing down the Vee when I did that. Stuck the inlet manifold back on, refilled the coolant and started the engine - noise still there :-(

So, by elimination, it must be either the pistons or little-ends. I guess the next step, short of pulling the heads (which I hate doing because of the exhaust manifolds), is a compression check to see if a cylinder is low. Maybe that way I'll only need to pull one head!

Å´hat I really don't understand is how an engine that was fine when I started the manifold swap should be instantly wrong as soon as I started it up with the new manifold? There's nothing with the manifold that should cause this. The two possibilities running through my head are either that something has somehow fallen into a cylinder, maybe a small nut, but I doubt even an M6 would get past a valve. The other possibility is that it somehow got water into a cylinder and it's hydrauliced a piston - it's fair to say that the weather has been a bit sh#t while I was doing the manifold swap but (I thought) I'd taken good care to cover the inlet ports when the manifold was off...

Frustrating day!

Andy.

p.s. Sounds to bad to try driving, so can't tell what it's like under load and the igniton is EDIS so I'm slightly weary of pulling plug leads, especially in drizzling rain, as it can give you one hell of a belt! ;)

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OK dokey, nipped home during lunch today and did a basic compression test on the cylinders. All plugs out, three seconds on the starter and each cylinder gave 170psi (plus/minus a couple of psi) on the gauge, with the exception #2 at almost 200psi :o So that would explain why it sounds like a diesel! ;)

Work permitting I'm going to try and get home before dark and see if I can get the head off to take a look into #2 cylinder. The good news is that bank is a lot easier to get open than the other side - small mercies.

AndyC.

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OK, so it was too much to expect that it would be obvious! :huh:

So, following from the very high compression test reading on cylinder 2 (195psi) and the fact that it's the easier of the two cylinder banks to get to, I pulled the head on this bank today:

5473673269_735077f565_z.jpg

_DSC4767 by AC72, on Flickr

First thoughts are "that's a lot of coking for an engine with less than 5,000 miles since a full rebuild" - but to be fair it's been running a badly-tuned (and I think over rich) Megasquirt for the last 6 months and before that it went to Italy and back in limp-home mode on the 14CUX, so a bit of coking is probably understandable.

The head wasn't much better. Number 2 is on the left. The oil is just stuff that leaked out from around the studs in the head when I lifted the head off:

5474270284_3ec14d09ed.jpg

_DSC4769 by AC72, on Flickr

Next step was to clean-up the pistons with petrol & a toothbrush. What was odd here is that cylinder 2 (the one I'm suspecting of being dodgy) cleaned-up really easily, but the others took a lot more scrubbing and didn't come as clean. The same story, but maybe to a lesser degree, with the head - number 2 cleaned-up better than the others.

Having cleaned things up and turned the engine over a tad to expose the bore of number 2, I saw this:

5473669801_a709a7bde4_z.jpg

_DSC4772 by AC72, on Flickr

It's not as bad as it looks, in that it's not actually a gouge in the wall, but just staining - I don't feel it if I run my nail over it. None of the other cylinders have this, and I'm guessing it must be fairly fresh as it looks like the sort of mark that would polish away as the engine was run.

Next I decided to drop the sump (again, my second least favourite job, exhausts being my first least favourite) and remove the piston from number 2. It came out easily enough and cleaned-up with petrol to look (to my untrained eye) OK:

5474266290_3de894c8d5_z.jpg

_DSC4775 by AC72, on Flickr

5473666645_a875575c9d_z.jpg

_DSC4777 by AC72, on Flickr

(the compression rings weren't gapped both in the same place when the piston came-out, that's a result of my cleaning). No obvious damage on the piston or con-rod and the little-end slides side-to-side nicely on the gudgeon pin but I can't detect any wobble at all.

The big-end bearing shells however don't look too clever for about 5,000 miles use:

5474267652_3a1c647c74_z.jpg

_DSC4773 by AC72, on Flickr

5474267148_c3e1a553ae_z.jpg

_DSC4774 by AC72, on Flickr

I'm trying to remember if I got them from Paddocks (the rebuild was in my pre-LR Series/Britcar days) or Real Steel. I think they could well be Paddocks and thus Britpart...

Last step was to take the valve out of the head and check them over:

5474263720_afe4e36594_z.jpg

_DSC4779 by AC72, on Flickr

Again they look OK, if a bit manky for 5,000 miles. The inlet valve does seem to be 'browned' from heat - I wonder if that's excessive?

5474263220_f94ee9e50b_z.jpg

_DSC4780 by AC72, on Flickr

So, no smoking gun :(

My theory is that the staining in #2 suggests that there has been water in there recently, and I'm guessing it got in when I had the inlet manifold off the engine for a week earlier this year. I'm trying to back-up that idea with the fact that #2 was easier to clean than the others is down to the steam cleaning it will have had when the engine fired. So, bearing in-mind that the engine was absolutely fine (at least with regards to nasty noises) before I changed the manifold and as soon as it fired-up with the new manifold the knock was there, so whatever happened was pretty instantaneous, I reckon maybe I hydraulicked that cylinder..

Although that doesn't explain the very high compression reading I got when I tested it on Tuesday, as by then all the water should have gone (and it was dry when I took the head off today). Also, if indeed that is what's happened, I still can't see what's making the noise, apart from the worn big-ends everything looks OK to me & I can't see that that amount of wear would cause such a noise and come about so instantly.

It could of-course be that focusing on cylinder 2 is a red-herring and the problem is actually else where?

More questions than answers!

I think the next thing to try is to stick the piston back in and put the valves back in the head and put the head back-on & try another compression test to see if the high-pressure is still there. If so, I'm going to (temporarily) swap the lifters from cylinder 2 and 4 and just see if the high compression moves to cylinder 4, in which case I'll suspect a dodgy lifter (only 6 months old and done bu^&er-all miles). Failing that, I'm going to put all the plugs in, turn her over on the starter, which in the past made a clonking noise, and pull each plug in-turn to see if the loss of compression in a cylinder makes a difference to the noise.

Any other suggestions? :D

Andy.

Edited by V8 Freak
Picture link amended
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Just a comment on the original nasty noise it certainly didn't sound to me like a big end noise which in my experience is an actual lower sounding knock sound...If I were you I would have a look at all the pistons and big end shells while you have it down to this stage, also carefully examine the crankshaft where the worn/damaged cap/shell is from.

Also if you cleaned the other pistons while they were in the motor are you sure there is no possibility any carbon finished up between the cylinder walls and the pistons because this could cause bad scoring of the liner.

May as well do this in the best way you can because you're putting in a fair bit of effort + head gaskets, sump gaskets, new oil etc. etc. So you will want to get it as right as you can other wise it will always be at the back of your mind.

Thanks for a well documented post.

Good luck...Hope it all works out for you.

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Just a comment on the original nasty noise it certainly didn't sound to me like a big end noise which in my experience is an actual lower sounding knock sound...If I were you I would have a look at all the pistons and big end shells while you have it down to this stage, also carefully examine the crankshaft where the worn/damaged cap/shell is from.

Also if you cleaned the other pistons while they were in the motor are you sure there is no possibility any carbon finished up between the cylinder walls and the pistons because this could cause bad scoring of the liner.

May as well do this in the best way you can because you're putting in a fair bit of effort + head gaskets, sump gaskets, new oil etc. etc. So you will want to get it as right as you can other wise it will always be at the back of your mind.

Thanks for a well documented post.

Good luck...Hope it all works out for you.

Cheers - luck seems to be needed at the mo!

I'm trying to decided how far to go with 'rebuilding' the engine at the moment. I always try to do as much as possible, so it's tempting to do all the big-ends, pistons, etc. whilst it's open, but factored against that I'm rapidly running out of credit with the boss, who's getting a bit fed-up of being left with the kids every weekend while I get oily! Things like oil and sump gaskets I always change in any-case. The head gaskets are pretty new and genuine parts ones (=£££) so I'd rather not bin them if possible. New big-end shells though are I think in-order.

Cheers,

Andrew.

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You really really ought to change head gaskets you know, they are single use only...

Do you have the tin ones or the composite? If composite go for Elring gaskets, V8Tuner and a lot of other places sell them.

Ar$e - they're Erling composites and not that old - seems a shame. I like need4speeds idea and an extra 5ft-lbs on the nuts! However I've long since resigned myself to throwing money at the Landie (lucky I don't have a 'proper' mistress!!!) so new head gaskets it is, along with big-ends. I'm not doing the mains as I can't see it's possible in-situ and I'm not pulling the engine out...

Cheers,

Andy.

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Did you try rocking the crank back and forth to see if you could hear the noise there?

you could crank the engine with number 2 (or other) pistons and rods removed, if you think you would still hear the noise doing that if it were there.

i maybe doing this wrong but 200psi / 14.7 (atmospheric pressure) = 14:1 compression. Seems a lot but 170 is 11.5 which seems a lot for a rover v8!

another thought would be to check slack in little ends in situ by rocking crank and feeling that the pistons move with the rods with no freeplay

Will

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