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68 Bentley T engine rattle under load.

3958 Views 104 Replies 12 Participants Last post by  Jim Walters
Hi all, I have been restoring my T1 5139 for the last 6 months and have completed the interior etc, however I have an annoying engine rattle under load which I cannot diagnose. L believe engine mileage may be 143k.

It feels like it is a collapsing hydraulic tappet, but all nice and quiet at idle or steady load or decellerating. I have had all the tappets out, tested them with the proper RR leak down tester and found 3 that would leak down very quickly at 2 seconds, 5 seconds and 7 seconds. Minimum should be 20 seconds maximum 90seconds. So the 3 weak ones were replaced with known good ones, put it all back together and the same rattle persists.

The noise is engine speed related, feels like it’s coming from the engine gallery area and is more like a hollow rattle than a knock. The noise increases if the load on the engine increases. It’s not the hydraulic brake pumps by the way. Those have been removed and the braking system has been converted to a conventional dual master cylinder and remote servos.

Would anyone have some ideas of where to look next? Weak valve springs? Cam looked good, no lobe wear.
Any assistance appreciated.
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Ok, started to get into the engine for a closer look. Sump is off and I have removed B3 Conrod bearing and cap.
Sump is clean, no debris in the bottom of it, no bolts that would cause my bag of bolts noise!
Photos shows condition of B3 Conrod bearing and crank journal, which for a suspected 143k mile engine looks very good to me. Certainly no evidence of rod knock. B3 cylinder wall on the thrust side shows some vertical wear but again doesn’t look too bad and no deep scratches. i haven’t been able to take a good photo of that though. I can’t detect any play in the small end bearing of B3 in the vertical plane, but does seem to have a little sideways wobble. Investigations continue onto the other cylinders. No smoking gun yet.
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And here is A1 conrod bearing. Looks all good.

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I don't think the racket is coming from the wrist pin on B3, there has to be considerable wear for it to make that much noise, but side ways play isn't good either.
I wonder if it could be worn on the wrist pin and/or piston bearing on the power stroke.
One may have to get it in that position to really tell.
Bearings look good so far.
Thanks Jeff, yes bearings look good and as you say they would need to be really bad to make that noise. Also had a look at the main bearings and these are in good condition. Had a better look at the bores and piston skirts too, they are not showing any alarming wear or damage. So no obvious signs at present.

Difficult To test for small end wear but I do understand what you are saying, that it might be a specific point in the power stroke where the wear is. these engines have interference fit wrist pins as I understand it. I will do some further digging tomorrow. Hopefully over the weekend I can rebuild the back suspension as two new shocks and a new spring cup have turned up today.
It's more likely to be A4 or B4, those are the cylinders in which the liner gets squeezed from corrosion and sediment buildup around the liner causing squeezing of the liner and momentary piston seizing causing damage to the skirt or ring lands.
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