[M635uk]

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.
Thanks
Ian

 

[M635uk]

Hi, thanks, but I can’t use a stethoscope when it’s under load I.e driving down the road and at idle it’s all quiet. To be more precise the noise is only there when car is accelerating. No noise when reving the engine.

 

[M635uk]

Yes, I could do with an old boy, take him up the road. It does it instantly you accelerate and it’s a very distinctive rattle. I will do a vacuum test as well to see if that indicates anything. Also might run it on 7 cylinders and see if that pinpoints anything.

 

[M635uk]

Will check the timing.
Thanks

 

[M635uk]

had pinking before in a different engine, more tinny noise than what I have here. Definitely sounds mechanical to me. But I will check timing thanks.

 

[M635uk]

Wow, some great responses here, overwhelmed by the input and and also the speed of replies. Great that so many ideas have come in. I will take a methodical approach. Ignition seems plausible seeing as its load related. Hoping its not gudgeon pin bushing…I will keep the updates coming. Many thanks.

 

[M635uk]

Ok time for an update. I checked the ignition timing at 1200 rpm, it was bang on 15 deg so set correctly.
I then moved onto the carbs and progressively richened both up, engine seemed to run sweeter but still this annoying rattle every time I went for a quick drive. Both carb jets are now about 4mm below the bridge of the carb. So I don’t believe it is pinking or I have timing issues or running lean.
it is definitely a hammering noise, quite a hollow sound, rattle like and engine speed related but only under load.
Any further thoughts?
Thanks.

 

[M635uk]

Also carried out a vacuum test, hopefully the attached photo shows it. Rapid Flickering around 21in Hg. Max 22 min 20.

compression test results on all cylinders shows around 120 psi mark except for cylinder 6, that one is down at 60 psi. So I carried out a leak down test on that cylinder, it’s leaking into the inlet manifold at TDC for that cylinder. So a leaky inlet valve I may have. Not sure if that going to account for the rattle though.

 

[M635uk]

Might try to see if I can identify if it’s related to a certain cylinder by grounding each plug wire in turn. Starting with cylinder 6…

 

[M635uk]

Ok, thanks will do

 

[M635uk]

Ok a further update now.
Swapped out a spare set of rocker shafts and rockers I had which were in very good condition. Still the rattle so it’s not weak/broken springs on the rocker shaft. Also isolated each cylinder plug lead one by one - rattle is still there so not able to identify it To a particular cylinder.

However I did manage to take a quick video of it. Link below at the bottom.
It sounds a little alarming but that’s probably my phone. The two rattles you can hear are from two quick accelerations I did. With this problem still being load related could this be a gearbox issue? Oil level in gearbox is correct.
As ever any further comments/ thoughts welcomed. Thanks

Bentley rattle

 

[M635uk]

Thanks guys, more to check it seems, especially external to the engine. I’ll have a look in the morning then away for a couple of weeks, need to get to the bottom of this to earn an early Xmas present !

 

[M635uk]

Ok, checked the viscous coupling seems fine, resistance when rotating by hand, it’s not close to anything so it’s not the fan that is hitting something to create the rattle. Pic shows my set up. Plenty of space.

is there an inspection plate to see the flex plate to the torque converter bolts? Or is it a gearbox out job? May get round to removing the belts to prove its not an ancillary item.
Exhaust isn’t blowing.
thanks.

 

[M635uk]

Also front engine mount is new, engine does rock a bit when revved but it’s not terrible. I can see how this would cause interference issues with the cooling fan but I have no radiator shroud for that to hit. So yes perhaps the two rear mounts should be changed out but rocking of the engine does not appear to be the cause here.

I have listened to a couple of examples of noise from loose torque converter bolts on YouTube and it seems a similar noise to what I have.

 

[M635uk]

Ok thanks, best to get it up in the air and check those bolts. 3 off I believe looking at the parts manual.

 

[M635uk]

Hi, belts are parallel, good spot re the two upper bolts but one doesn’t locate onto anything. Afraid I am unravelling 54years of other peoples work on the car. Removing the belts will help narrow down the issue. And yes it could be a cracked flexiplate. 😕

 

[M635uk]

Away from the car for two weeks now so updates will follow later. Thanks.

 

[M635uk]

Ok finally managed to get at the flexplate to inspect that. All bolts (3 off) are tight, no cracking around the bolt holes but of course I can’t view where the flexplate bolts to the crank.
Also removed belts and tested and noise still present. So it’s looking like I have to get the gearbox out to inspect the plate fully. I am also thinking the torque converter may be the culprit. Car has 143k miles so it could be failing - especially as it’s a load related noise and the converter is a load related device.
final test I want to do is a stall test with the brakes applied and the the throttle open, see if the noise is there then.
I intend to get the car into my garage, to take out the gearbox, 3ft of the car will have to stick out of the garage. I have some 4 tonne axle stands to get the car up in the air, and a transmission cradle for my jack. Any advice on dropping the gearbox? I have to remove the gearbox anyway to resolve a bad rear crankshaft oil leak with an upgraded seal modification. Maybe that leak is a clue that something isn’t right in that area. Some pics of the flexplate bolts too.
link to the procedure I will copy for gearbox removal although it’s for a spirit. Australian RR Forums: Gearbox overhaul SZ 3-speed

 

[M635uk]

Thanks, good idea re paint, endoscope and securing the torque converter.
Why does the starter have to be removed? Thanks.

 

[M635uk]

Further update, having removed the front and rear gearbox inspection plates to view the flexplate I had to move the car to the side of the garage. I ran the car and then did a stall test, no noise. I then ran the car around the local estate - no noise. Got back and had a look at he inspection plates - no tell tale signs of gouging and contact. Put the car to the side of the garage.

So now my noise has disappeared, which is both good and bad news. Will it come back? Did my stall test somehow correct the issue, did it do some magic in the torque converter to correct a loose turbine blade? I still need to remove the gearbox to do the rear crankshaft seal mod so will continue with that plan. Only other work I did was to loosen all 3 engine mounts to allow engine to be lifted a little to aid flexplate inspection and then refit.
Bizarre.