Rattle and knocking from bellhousing

Drivetrain problems

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Rattle and knocking from bellhousing

Postby mlewi6 » Wed 28.10.2015, 01:45

I am three years into a project on my '91 Fed Elan - and I thought I was about 99% done :( Thanks to this incredible forum I have been able to pull the engine and put in a new clutch with all the associate things you renew - pumps, belts, hoses etc. I put in a new driven plate, pressure plate and thrust bearing, had the flywheel resurfaced and put the new bolts in. Finally everything is back in and it ran up fabulously. On the test drive I got about 300 yards before a tremendous rattle started up. The rattle/knocking sounds like something big and loose turning around. It varies with the speed of the engine and depressing the clutch decreases it momentarily and then it start up again. It is worse on the overrun after throttling up the engine. The only thing we can think of is the sleeve/bush in the crankshaft that the input shaft sits in. It wasn't touched in the rebuild project. After all this time I am not keen to chase something down that I don't have to, but it would seem as if I should take the transmission off (on its own this time) and explore. Any ideas or clues would be much appreciated. And thanks again for all that contribute to this invaluable source of knowledge.

Martyn.
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Re: Rattle and knocking from bellhousing

Postby Brit-Car-Nut » Wed 28.10.2015, 03:39

It would help if you put your location into your profile. You might have someone close enough by that would come over and give you a hand diagnosing the problem.

You might be able to narrow it down by using a stethoscope or use a long screwdriver as a hearing aid around that end of the car with the engine running to try to narrow down the area actually making the noises.
Unfortunately, there are many possible causes of rattles:
The honeycombs of the Cats will kick up a ruckus if they break up
The drive end of the CAS has been known to crack at the rollpin hole and that would allow a lot of free-play between the shaft and the drive dog which could sound like a rattle but you should also experience a degrade in the performance
Any chance that the bolts for the Axle Center Shaft have come loose or the bearing inside has failed or the cupped washer is out of position?
The retaining ring on the throw-out bearing is also finicky and if it de-clipped, the TOB could be rattling around
The pilot bush is suspect especially if you had some trouble getting the gearbox to align with the engine during reassembly

I would suggest starting with the easiest thing to test, being the CAS (remember to mark the housing to the head to preserve the timing) followed by tapping the cats to see if either has failed and then before removing the gearbox, check the Center Shaft for proper fit and fitness and, then, if you don't find anything, pulling the gearbox sounds inevitable. It isn't a lot of fun but quite doable.

There is a good write-up on the removal process in the WikiLEC. Here is a link: Gearbox Removal
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Re: Rattle and knocking from bellhousing

Postby mlewi6 » Wed 28.10.2015, 04:04

Thanks for the suggestions. I have done the "stethoscope" approach now and the rattle and knocking is coming from the bell housing. Underneath the car you can feel it with your fingertips on the base of the bell housing. I put in a new thrust bearing and checked that circlip numerous times, which may mean not a lot. There wasn't a great deal of difficulty with the alignment of the transmission onto the engine. This sound was not there at first during engine testing, and only started after driving about 300 yards - so I am guessing that the load caused it to happen. Now it is there all the time, aside from when the clutch is depressed it declines, but comes back - even with the clutch depressed. I also updated my profile with the location - thanks for that suggestion - I feel that is the most productive I have been today. It sounds like a chain is whipping around the input shaft and hammering on the bell housing.

Thanks again,

Martyn.
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Re: Rattle and knocking from bellhousing

Postby mlewi6 » Wed 28.10.2015, 04:07

...and that is a fabulous wiki on gearbox removal. Although I don't want to face it, the words of encouragement and step-by-step procedures and pictures and very much appreciated.

Thanks again,

Martyn.
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Re: Rattle and knocking from bellhousing

Postby Brit-Car-Nut » Wed 28.10.2015, 14:24

Unfortunately, the clutch could have broken up too. You will need to remove the gearbox to see what has happened. I would strongly suggest avoiding any more running until it is apart. I hope it turns out to be insignificant and just a bit of labor to sort it out.
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Re: Rattle and knocking from bellhousing

Postby Enright » Wed 28.10.2015, 15:40

mlewi6 wrote:...and that is a fabulous wiki on gearbox removal. Although I don't want to face it, the words of encouragement and step-by-step procedures and pictures and very much appreciated.

Thanks again,

Martyn.

That sounds horrible. Sorry to say but I think you know already - there's no easy way round this one. The gearbox has got to be split from the engine again. Don't even start the car or you could end up with an "inspection port" in your bell-housing that wasn't part of the original design. All it takes is for something to jam between the flywheel and the housing, and bang, crunch, bye-bye wallet it was nice knowing you.
At least with the parts being new the only expense should be your time and the skin off a few knuckles.
With luck you'll just find that it's a bolt that wasn't torqued-up properly, can pop it back in and put it down to experience.
Striking fear into the hearts of duplicate posts everywhere...! :P

BCingU,
Neil ;-)
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Re: Rattle and knocking from bellhousing

Postby mlewi6 » Sun 01.11.2015, 06:26

Its been a busy day...but thanks once again to the superb support here I have the transmission now out of the car. Of note, the front of the sub-assembly on US cars is not like the UK cars and the great picture by picture wiki. It is held to the support frame by two hex head set screws which are very fiddly to get at, and then a bolt that goes through and acts as a retainer for the PAS pipe. I'll see if I can get pictures when I reassemble to post here.

I have also thought of a better word to describe the sound it was making - clatter. So, with the bell housing now split everything basically looks OK. The thrust bearing and circlip are fine, as is the cover and clutch plate. The flywheel all seems OK as well. All look as they were fitted new a couple of weeks ago. However, I am not sure what the bush/bearing should be like where the input shaft ends. If I stick my finger in the hole in the middle of the crankshaft it feels like a loose plastic cup which does indeed rattle - but it seems odd that this could be the source of such a loud and metallic clattering. I can't find to much information about this bush. Any ideas or advice would be very much appreciated.

Martyn.
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Re: Rattle and knocking from bellhousing

Postby Brit-Car-Nut » Sun 01.11.2015, 13:22

When you rebuilt the engine, did you have the crankshaft cleaned, measured and possibly resized? Before you did that, did you remove the crankshaft pilot (spigot) bushing/bearing? If not, did you replace is as part of the new clutch? If not, did you check it to make sure the cleaning process didn't remove all of the internal grease and now it is running dry? That could make for a fairly noisy scenario. Roller bearings require decent lubrication.

The Lotus part number A100E6248S is now obsolete but Rock Auto shows the pilot bearing to be the same as an A/C front bearing as well as an Alternator front bearing, so getting a replacement should be fairly straight forward. I answered your email with all of the details and part numbers from most common US DIY supply stores.
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Re: Rattle and knocking from bellhousing

Postby Brit-Car-Nut » Sun 01.11.2015, 19:34

Martyn: After our discussion, I went to the shop and verified the Lotus AND GEO do not use a 1970s style input shaft so the floating plastic spacer is fine as it just helps to keep the input shaft in position, not centered on the crankshaft. There are no bearings, either roller or ball, so that is no longer a worry regarding your noises.

It is obvious that Rock Auto have a bad reference for the input shaft bearing.

It is hard to teach old dogs new tricks... but I still like to try to be better educated.
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Re: Rattle and knocking from bellhousing

Postby mlewi6 » Mon 02.11.2015, 02:08

Quite right - the input shaft is floating and is not captive in a pilot bearing. I have now found that the flywheel was lose. I have no idea how that could have happened as we torqued it up very carefully. All eight bolts were about 2 to 3mm out thus it was "wobbling". That was the likely cause of the noise, but now I am mystified as to why the flywheel would seem to come lose after a road test.

Thanks,

Martyn.
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Re: Rattle and knocking from bellhousing

Postby muley » Mon 02.11.2015, 11:31

Good to hear you have discovered the problem. Maybe the flywheel wasn't seated correctly when tightened up?

Rgds


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