Engine vibration 1HD-T

[frank rabbets]

I went to see a 12 cylinder 80 a few years back and on idle I could see a definite vibration and movement in the engine. On driving it this all went away. I assumed it was an imbalance in the injection or compression in one cylinder as I had seen this on other cars.

 

[StarCruiser]

A 12 cylinder 80…[emoji33][emoji33][emoji33][emoji33][emoji4]
Don't let Shayne read that, he'll be on a mission to track it down as his entry into 80 ownership. [emoji6][emoji4]

 

[StarCruiser]

I went to see a 12 cylinder 80 a few years back and on idle I could see a definite vibration and movement in the engine. On driving it this all went away. I assumed it was an imbalance in the injection or compression in one cylinder as I had seen this on other cars.

Once I get to find someone who will do a compression test on it I will be a bit wiser as to why things are how they are. It used to be so smooth [emoji20][emoji20]

Thing is, you can't see it, the engine is solid as a rock. You just feel it vibrating the car and things rattle[emoji35]

 

[Dave2000]

I went to see a 12 cylinder 80 a few years back and on idle I could see a definite vibration and movement in the engine. On driving it this all went away. I assumed it was an imbalance in the injection or compression in one cylinder as I had seen this on other cars.

Sorry running off topic a little but, I used to drag/daily drive a 1976 XJ 5.3C up until I moved to Spain about 10 years ago, Of course I got to work on these magnificent engines quite a lot, whenever a customer had said there was a vibration it was invariably the front four spark plugs worn to nothing, they were a pain to fit as you had to remove a mass of wiring and the AC compressor just to see them! Many 'garages' just fitted the 'easy six' as the other two hidden by the throttle tower also a pain to remove, essentially doing half a set of plugs. Fuel consumption could be as good as 22 MPG if they were setup correctly. Mine was nearer 12 but then mine was sleeved to 6.0 with 12 x 4.2 injectors, aluminium flywheel, throttle bodies you could put your arm down...oh and a Getrag five speed manual to boot....literally!!

Saddest day of my motoring life selling that beast....................

regards

Dave

 

[frank rabbets]

Ah, just twigged should have read "12 valve".

 

[StarCruiser]

Ho hum…was a nice dream while it lasted…[emoji6]

 

[clivehorridge]

Just catching up on this thread Rich, and if I've read it correctly have you diagnosed the problem to an injector seal?

If not, it's worth having a check of the valve springs (Dave's post #81 got close) as I've had (in the past and not on the 80) a broken valve spring that gives the same symptoms.

Sometimes they're not so evident especially if double (concentric) springs are used (I don't remember if the 12v 80 has single or double springs).

Just a thought.

Best of luck with it...

 

[StarCruiser]

Ah, that makes sense Clive and thanks. In fairness everything so far suggested has made sense but I can see how that would do it. When I took it to S&S diesels they seemed pretty sure it had a misfire and said injectors or a valve so your theory fits well there. Not sure how I check, pull it apart I guess and look under the buckets. Compression test is my next stage but I'm drawing a blank locally on someone with a compression tester.

Edit, no Clive alas that was wishful thinking on my part. The vibration made me pull the injectors and take them for service but I seem to have made a pigs ear of putting no5 back despite being as clean as I could be and vacuuming out the holes. It let go on Sunday morning, initially and before I got to look st it I suspected head gasket or a glow plug problem. Fortunately it's just an injector seal.

 

[StarCruiser]

Just had a numpty moment having thought to ring the nearest garage in the village. Yes, got a compression tester that says it will do diesels but not sure if we will have the adaptor unless you bring it in for us to try. [emoji47][emoji19]

Progress at least.

 

[Dave2000]

Ah, just twigged should have read "12 valve".

There was I in nostalgia land.............

regards

Dave

 

[StarCruiser]

There was I in nostalgia land.............

regards

Dave

It was good while it lasted wasn't it Dave?

 

[Dave2000]

It was good while it lasted wasn't it Dave?

Sure was, normally I drove the Jag to the event and raced 'as is', on the one occasion I used a Range Rover to drag it to Santa Pod on a four wheel trailer, a trailer tyre blew and the wire ripped the arch off the trailer and scratched my recent bare metal re-spray, we (with my petrol head daughter) got to the venue to find it rained off. The second worse memory in my car memories.

regards

Dave

 

[frank rabbets]

I suspect if a valve spring was giving problems on an 80 diesel you would have had the valve hit the piston. On the 24 VALVE 80 there is a minute valve overlap of only a few thousandths of an inch on TDC overlap.

 

[IRLGW]

whats the frequency of the vibration?

 

[StarCruiser]

whats the frequency of the vibration?

It's even with the engine speed. Worse when cold but obviously there when warm. It runs well, starts well, no appreciable smoke apart from a little black on hard acceleration (which is to be expected) and plenty of power.

I've located a compression tester that I can borrow and use, hopefully this week. [emoji3][emoji3][emoji3]

 

[IRLGW]

fuel economy?

 

[StarCruiser]

No idea. I'll have to check but used to be around 24.5 MPG on a run.

 

[StarCruiser]

Ok, at long last I've given the old girl a compression test today. [emoji3] TBH, I was dreading it in case I found something.

The results are as follows:-

Cyl - Psi
1- 500
2- 520
3- 485
4- 480
5- 485
6- 490

All on a calibrated gauge after 7 revolutions (which is where it evened out).

Glow plugs, after never being out in this country came out very easily.

Also, a quick check has revealed the two separate pulleys at the front of the crankshaft are still in line despite my AC compressor seizing up and no doubt putting a lot of strain on one of them.

Where to now? The garage were very helpful and I had a chat with them after I did the test with their gauge.

Their thought was to check pump timing. But I haven't been near it I protested, although I did do the cam belt earlier this year long before the vibration manifested itself. Worth checking both they said.

I will check the belt again. But It is done on timing marks so unless I've had my eyes in back to front I cannot see how I would have got it wrong.

Worth a check anyway i guess just to rule it out.

 

[clivehorridge]

I suspect if a valve spring was giving problems on an 80 diesel you would have had the valve hit the piston. On the 24 VALVE 80 there is a minute valve overlap of only a few thousandths of an inch on TDC overlap.

I take your point Frank, but I wouldn't rule it out. I'm also not advocating Rich taking the head off yet to investigate the condition of the valve seats, but a prod around the springs with a screwdriver checking their integrity would only cost a cover gasket, and a couple of hours' fettling.

It seems he's getting no closer to the problem, and for sure its not nothing, so it must be something.

In my case, and I don't remember what engine it was, the valve operated correctly with the inner spring broken, it just didn't make a good seal which allowed some compression escape, enough to cause a lumpy idle. It appeared to drive ok.

I have no idea if the variance between 480 and 500 psi is significant, on the readings, but if it is, it could be worth starting with a grind of the valve seats, it's certainly cheaper than the alternative probable causes.

Its only 4% down in the extreme so I'd imagine the readings are even enough, unless they're all down which is unlikely. Is the firing psi a published figure, does alone know?

A quick edit edit here after doing a bit of gluegleing... and I'm only quoting what I found

Standard 498psi (manual says 500psi);
minimal acceptable 360psi;
Compression Ratio 18.6:1
One guy on ih8mud got readings of 450 psi on 5 and one at 430.

So I recon Rich's readings are good and even (regular) enough to rule out a bad valve seating...

 

[StarCruiser]

The guys in the garage all seemed to think those pressures were good enough to rule out compression issues and said if they were within 10% then they were plenty good enough.

To check valve springs it's a cam off job, which I hope should be drama free.

It's on my list to look at Clive, especially now I've done the compression test.