Vibrations update

[mike@thenook]

Andrew kindly lent me his compression tester so I found an hour this afternoon to check each pot; they all came up at just under 9bar so not a problem there.
What I did realise though that when cranking the engine (coil and fuel pump disconnected) to check the compressions there was a distinct rumble coming from the engine - foot on the clutch or off it made no difference.
So, I'm thinking I have a crank bearing problem again but it was properly checked, polished and new bearings AND I had the rumble with the old different crank.
I guess the only answer is engine out and stripped again but having done it once and I still have it I'm at a bit of a loss to understand how the crank can be the problem. Also, the oil pressure is excellent....
Baffled I am!

[Andrew S]

Is there anyway that the sump is hitting the crank?

If you have recently fitted new shells to the crank, you cant possibly have any play as yet if at all and as you have good oil pressure, it must be fine.

[mike@thenook]

I'll certainly have a look at the sump but it's a rumble/in-balance rather than metal to metal..
i tend to agree on the shells.

cheers!

[mole42]

Hi, have you changed the crank? Your comment about "the old different crank" makes me wonder.
If you have changed the crank and the rumble is the same as before, then it's not crank related.
Have you checked the runout of the flywheel? Is the fan fitted at the front? Could it be a problem with the front pulley? Could it be the clutch or pressure plate?

Richard

[Andrew S]

Just to recap, you had a vibration before the engine didn't you and if so, was the same as you have now? In other words is this a different vibration? Was the vibration there on the new rebuild from day one or has it developed since? Is it possible a clutch drive play can be fitted round the wrong way and its fowling the flywheel bolts?

[wilf]

Mike - this is a manual gearbox? My suspicions run to the spigot bearing. Does the noise change clutch in/out?

[Staggard]

Mike - this is a manual gearbox? My suspicions run to the spigot bearing. Does the noise change clutch in/out?

Wilf your not reading the posts again

[Staggard]

A rumble usually comes from main bearings or from ball/roller races. Silly question but I guess you have checked the viscous and disconnected the alternator/pas pump. I have heard a loose flywheel make a rumble noise but I guess pressing the clutch down would have stopped/reduced that.

[Staggard]

Wilf your not reading the posts again

Unless you disengage the clutch the engine and gearbox turns as one lump.

[wilf]

Wilf your not reading the posts again

LOL, quite right!

[mike@thenook]

Hi chaps,

Yes, its the same rumble as I had before I re-built the engine and used a different crank with new shells etc., it is there with foot both on and off clutch so I'm ruling out transmission and logically it cannot really be the crank. It really starts to appear at 2,000 rpm so with the car in od 50/60 is ok, 70 + (on a track of course) is awful!

I've tried in the past disconnecting the PS pump and all the drive belts and it didn't go away so I guess (and I've done a lot of it!) it really can only be the flywheel out of balance a tad or the front pulley - I think I need to try again and disconnect all these bits and run it plus get a different front pulley - failing that get the damn box out again (a job I loathe) and have the flywheel checked.

[jbuckl]

I can highly recommend 'vibration free' to provide vibration diagnostics & solutions, for when all usual / normal causes have been checked and ruled out.

http://vibrationfree.co.uk/

An automotive stethoscope is a useful tool for location of rumbles though....

http://www.ebay.co.uk/itm/Automotive-Mechanics-Stethoscope-Engine-Diagnostic-Tool-Car-Van-Super-Sensitive-/120842366255

Hi chaps,

Yes, its the same rumble as I had before I re-built the engine and used a different crank with new shells etc., it is there with foot both on and off clutch so I'm ruling out transmission and logically it cannot really be the crank. It really starts to appear at 2,000 rpm so with the car in od 50/60 is ok, 70 + (on a track of course) is awful!

I've tried in the past disconnecting the PS pump and all the drive belts and it didn't go away so I guess (and I've done a lot of it!) it really can only be the flywheel out of balance a tad or the front pulley - I think I need to try again and disconnect all these bits and run it plus get a different front pulley - failing that get the damn box out again (a job I loathe) and have the flywheel checked.

[milothedog]

Hi chaps,

Yes, its the same rumble as I had before I re-built the engine and used a different crank with new shells etc., it is there with foot both on and off clutch so I'm ruling out transmission and logically it cannot really be the crank. It really starts to appear at 2,000 rpm so with the car in od 50/60 is ok, 70 + (on a track of course) is awful!

I've tried in the past disconnecting the PS pump and all the drive belts and it didn't go away so I guess (and I've done a lot of it!) it really can only be the flywheel out of balance a tad or the front pulley - I think I need to try again and disconnect all these bits and run it plus get a different front pulley - failing that get the damn box out again (a job I loathe) and have the flywheel checked.

If it were the flywheel I would have thought it would show up stationary when the engine is at those rev's as well as in any gear at the given RPM

I'll say it for the sake of it but I'm no doubt think it would have been checked, but how close is the manifold to the short steering shaft (You did say you had headers I think)


I have seen/repaired cars running with a loose flywheel and also a Transit V4 van with a snapped crank, trust me me you wouldn't have been using it if you had either of those faults.

[jleyton]

This is probably a crazy suggestion but when you've investigated so many other possible causes just maybe the really unexpected could be the cause.

You're not running with one cylinder down are you ? From experience I know that it's sometimes difficult to spot that you're running on 7 rather than 8 .

Cheers

Julian

[LAMBRETTLAD]

I can highly recommend 'vibration free' to provide vibration diagnostics & solutions, for when all usual / normal causes have been checked and ruled out.

http://vibrationfree.co.uk/

An automotive stethoscope is a useful tool for location of rumbles though....

http://www.ebay.co.uk/itm/Automotive...-/120842366255

I've used vibration free ,and they are the best 11/10, you find out the problem and possible cures very quickly ,saves unsettled sleeps !