MGB & GT Forum

OK, I'm pretty sure I know the answer already, but I'm hoping that MAYBE I might get lucky?

I know that it is pretty much impossible to change out the MGB clutch without pulling the engine, at least for us mere mechanical novices. But what about the throw-out bearing? Can it be replaced without having to do a complete engine pull?

Reason I ask: I just finished doing some work on the engine over the winter months, and in the process had to disconnect my air conditioning lines and remove the compressor. And I JUST had the entire A/C system recharged with fresh 134a the other day. Now when I am driving, I am starting to hear what could be the early signs of the throw-out bearing nearing its end. A complete clutch replacement (TO bearing included) was performed shortly after acquiring the car back in 2004, and I would estimate in these 20 years that less than 30,000 miles has been put on the odometer. It might be too early to be 100% certain it's the TO bearing; more driving is going to need to be done. What I heard yesterday was intermittent and only occurred a few times; it might have only been on certain road conditions (uphill, downhill, etc...I wasn't keeping track). But I'm just trying to steel myself ahead of the final judgement. I really don't want to have to evacuate my A/C system again to pull the engine, and then pay another $135 to get it recharged! Would have been nice if this manifestation had started happening last year, I could have tackled it already.

My luck is never that good; this happening now is just SOP for me!
Brando

You do have to pull the engine to change the throw out bearing. But pulling the engine on an MGB is a fairly easy task (as these things go). There is always the question of whether to pull the engine alone or engine/gearbox as a unit. There are pros and cons to each approach. I've done both and I'm not sure how I'll do it next time. What you save in one way you tend to pay in another.

When you change the throw out bearing, also change the clutch fork pivot bolt and bushing. These are only a few dollars but can only be changed with the engine out. Unless the clutch is brand new I'd change at least the disk. It is so inexpensive compared to the effort required to change it that it is false economy not to change it, IMHO.

If your rear main seal leaks then this is the opportunity to put in a Speedi-sleeve and a new seal. If it doesn't leak, I'd smile at it and talk to it kindly, but leave it alone.

But - the throw out bearing doesn't usually make noise when driving. Problems usually manifest themselves when you step on the clutch pedal. At other times it just rides lightly against the pressure plate. I suppose it could make noise just idling but it should get worse when you press the pedal down. What problems are you experiencing and what do they sound like?

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Terry Ingoldsby
terry.ingoldsby@DCExperts.com

At what clutch pedal position do you get the noise?

Can you describe the noise a little more? (grid, screech, ...)

When the noise occurs do you feel anything? (through the shift-lever or clutch pedal)

Can you snake a borescope through the clutch fork boot and have a look?

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I was addicted to the hokey pokey but I turned myself around.

prop-a-gan-da: When a British person takes a close look at something

When the weather gets a bit nicer drive it over here. Maybe I can help ya diagnose the problems. Bangs, pops, squeaks, chirps, grinding noises, and thumps are not normal.

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Si Vis pacem, para bellum

UPDATE: Thanks to everyone that has responded so far. My initial assessment of throw-out bearing may not have been the problem at all. My friend Aridgerunner called me to discuss, and suggested that the sounds I heard may in fact be the input shaft bearing, and perhaps since the car had been up on stands for so long while getting work done, might have been a bit dried out.This would explain why I heard the slight scraping (?) noise at the beginning of the drive, but not later on. I took the car out for a short 8 mile jaunt yesterday (between rainstorms), starting down the same roads where I heard the noise initially, and nothing...ran and sounded normal. Perhaps the oil had made it's way into/onto the bearing and silenced any noises?

I'll be keeping my ears open for this, but...fingers crossed...perhaps it was nothing; just a poorly reasoned jump to conclusions on my part. It would be nice if I could get a few years out of the air conditioning's newly injected 134a refrigerant before having to evacuate it all prior to an engine/transmission removal. The stuff ain't exactly cheap, and unfortunately the shop I took it to did some damage to my car in the process, so I'll have to find someplace else to go for future A/C recharges. Because I sure as heck ain't going back there!!

Thanks again.
Brando

I'm not clear if, by input shaft bearing, you mean the input shaft into the gearbox or if you mean the pilot bushing (where the input shaft rides in the end of the engine's crankshaft). The latter is a bronze bushing and no oil flows to it. Oil does move around the gearbox, so the former could conceivably have reached it if dry (which seems unusual).

Again - did you hear the noise when you stepped on the clutch, when idling, when driving? The answers to these questions provide clues as to what you were experiencing.

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Terry Ingoldsby
terry.ingoldsby@DCExperts.com

Yes, the pilot bushing. Those bushings are the Oilite type. They contain approximately 20% oil by volume. Now keep in mind I'm no chemical engineer but my thought was because the car sat so long maybe the bushing dried out a bit and simply using it would get the oil back to the surface.

Honestly, I think most of the noises Brando heard were due to work the AC shop did. Brando didn't mention it but I will. They actually sprung his hood by not understanding how the support works. That caused the hood to be lower on the right side, right over the alternator, and the two were making contact. In his car the alternator sits much higher due to the AC unit.

All's well that ends well.

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Si Vis pacem, para bellum

when ever i pull an engine with ac i un bolt the compresser and put it off to the side with lines still attached.

So you're saying not much difference as far as work, to just pull engine, like a lot cars? beside propping up the trans, what other issues is there/
thanks

If you pull only the engine, you don't really need to prop up the gearbox. The crossmember will hold it adequately in place.

If you pull only the engine, you may find that it slips right back into place as slick as a whistle. Or, you may find that you spend several hours and multiple tries to get the gearbox input shaft lined up with the clutch and pilot bushing.

If you pull the engine and gearbox as a unit, you will lose an hour or two unhooking the gearbox from the car. The crossmember isn't as hard as everyone makes out. Basically, you undo the four bolts on the sides of the crossmember and let the gearbox hang down (using a floor jack to lower it). This exposes the bolts on the gearbox mounts (and pedestal) and makes it relatively easy to unhook. Connecting it is the reverse procedure. It is much easier to reconnect the gearbox to the engine with it out of the car.

Particularly if you pull the engine and gearbox as a unit, you need to have some leveling device on your hoist as you need to change the angle throughout the pull. It helps even if you don't pull the gearbox.

But, basically, you can pull the engine alone and hope that it will slip in. Sometimes it does. In that case, you've saved several hours of disconnecting and reconnecting the gearbox. Or you may waste more than that much time getting it to slip in. Pulling the gearbox costs time, but a fixed amount of time. The question is, do you feel lucky?!

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Terry Ingoldsby
terry.ingoldsby@DCExperts.com

It is not possible to change the Thrust bearing without removing either the gearbox or the engine.
Sorry to bear bad news.