Replace rear main seal, with clutch? (Part quality issue.)

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Well, I have to say, it seems like half the people here think it's a good idea to replace the seal and half don't. And everyone makes pretty good arguments. So I'm a bit confused. Also, I talked to two well recommended transmission shops. One said, if it's not leaking not to replace it, but mainly because aftermarket parts are low quality. The second said, it's easy to do, he always recommends doing it, after more than 100k miles it's probably starting to dry out, he can get the part from Mazda, and he's never had one come back leaking. The only consensus in this thread seems to be to use the Mazda seal, if it's replaced.

Regarding the flywhell, the two transmission shops I talked to also both said they would pull the flywheel to resurface it, in which case I'm thinking maybe I should just buy the Luk flywheel for $72, which is cheaper than what they're charging for resurfacing.
If you are going to remove the flywheel, then why not replace the seal too. Just know that you are looking at the possibility of mechanics error or bad seal (even OE) and could see a leak. What is life without taking chances, right?

I typically do not replace seals unless they are leaking, even at high mileage or age.
 
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Smart move to replace flywheel with new. I’ve had several clutch jobs ruined by resurfacing equipment out of “true”. Regarding the rear main seal…there’s most likely a crusty ring on the crank journal with that mileage. Getting a new seal to line up exactly where it won’t leak is critical. If it’s dry now leave it alone. It will last the life of the engine.
 
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Well, I have to say, it seems like half the people here think it's a good idea to replace the seal and half don't. And everyone makes pretty good arguments. So I'm a bit confused. Also, I talked to two well recommended transmission shops. One said, if it's not leaking not to replace it, but mainly because aftermarket parts are low quality. The second said, it's easy to do, he always recommends doing it, after more than 100k miles it's probably starting to dry out, he can get the part from Mazda, and he's never had one come back leaking. The only consensus in this thread seems to be to use the Mazda seal, if it's replaced.

Regarding the flywhell, the two transmission shops I talked to also both said they would pull the flywheel to resurface it, in which case I'm thinking maybe I should just buy the Luk flywheel for $72, which is cheaper than what they're charging for resurfacing.

For $72, absolutely replace it. I don't bother with resurfacing anymore, learned my lesson on a Saab 9-3 years ago. The OE flywheel just didn't have enough material, and after the machine shop took .010 or whatever off the flywheel the car started eating clutches every couple thousand miles.

I went round and round with my service manager trying to explain the reasoning (it was an expensive flywheel), and he swore it was a clutch or pressure plate problem. However, I installed an OE clutch kit. The only variable was that the flywheel had been cut. After a THIRD time warranting the job, I refused to proceed unless I was given an OE flywheel to install. They caved, and the car never came back.

Put in a new one, and leave the rear main alone.
 
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For a long time I've been of the mind that if it isn't broken don't fix it and if it is broken replace only with OE. (with only a few exceptions)

That has only gotten stronger with current supply and quality issues.

If it isn't leaking I would leave it alone.
 

cb474

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Well, by my count seven people have said to leave the rear main seal alone, if it's not leaking, and three have said to replace it with an Mazda part, because it's not a big deal if they've got the tranmission out and flywheel off anyway. And some people were equivocal, so I didn't count them either way. Perhaps I should just go with the wisdom of the crowd and leave the seal alone, unless it's leaking.

For what it's worth, this it the design of the part, there's a retainer with the seal built into it:

Better images:

One of the transmission places looked up how it's supposed to be installed and said it also requires some silicone sealant placed somewhere, so that it doesn't leak from the pan, if that makes any sense. I think that's what he said.
 
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Smart move to replace flywheel with new. I’ve had several clutch jobs ruined by resurfacing equipment out of “true”. Regarding the rear main seal…there’s most likely a crusty ring on the crank journal with that mileage. Getting a new seal to line up exactly where it won’t leak is critical. If it’s dry now leave it alone. It will last the life of the engine.
Many newer cars available with a stick shift also use a dual-mass flywheel. The OE recommendation is to replace it. If a machine shop can’t machine a regular flywheel “true” and flat, imagine the struggle they’ll have when setting up a dual-mass for machining.
 

D60

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Well, by my count seven people have said to leave the rear main seal alone, if it's not leaking, and three have said to replace it with an Mazda part, because it's not a big deal if they've got the tranmission out and flywheel off anyway. And some people were equivocal, so I didn't count them either way. Perhaps I should just go with the wisdom of the crowd and leave the seal alone, unless it's leaking.

For what it's worth, this it the design of the part, there's a retainer with the seal built into it:

Better images:

One of the transmission places looked up how it's supposed to be installed and said it also requires some silicone sealant placed somewhere, so that it doesn't leak from the pan, if that makes any sense. I think that's what he said.
Yep, looks like the Toyota 3.0/3.4 setup and probably others. Except those aren't integral, ie you can press the seal out of the retainer. Those also seal against the oil pan.

I'd replace it on my own vehicle but those with more wisdom say to leave it. I'm not disagreeing with the pros, just saying how I'd handle my own property, even if I was potentially making a mistake....
 
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Well, by my count seven people have said to leave the rear main seal alone, if it's not leaking, and three have said to replace it with an Mazda part, because it's not a big deal if they've got the tranmission out and flywheel off anyway. And some people were equivocal, so I didn't count them either way. Perhaps I should just go with the wisdom of the crowd and leave the seal alone, unless it's leaking.

For what it's worth, this it the design of the part, there's a retainer with the seal built into it:

Better images:

One of the transmission places looked up how it's supposed to be installed and said it also requires some silicone sealant placed somewhere, so that it doesn't leak from the pan, if that makes any sense. I think that's what he said.
The seal being integrated in a cover like that will make it less prone to installer error, I was not familiar with how Mazda rear mains were. Sealant where it meets the oil pan isn’t really a cause of concern. Many techs are sloppy with their rtv and sealant work, but sloppy or not, they will usually get it to seal at least.
 
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I would. I did a clutch job over the summer to my van, the slave cylinder failed. I changed all clutch related parts including the flywheel, RMS, front transmission seal, and the transmission tail shaft seal. I don't ever plan on doing it again. ;)
 
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Some engines need a special tool to insure a proper rear main seal installation. If it’s not used, there is a high probability it’ll leak.
 

cb474

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The seal being integrated in a cover like that will make it less prone to installer error, I was not familiar with how Mazda rear mains were. Sealant where it meets the oil pan isn’t really a cause of concern. Many techs are sloppy with their rtv and sealant work, but sloppy or not, they will usually get it to seal at least.
Well, I went ahead and had the mechanic do the rear main seal, when he did the clutch. I got the car back on Wednesday. I was taking the undercover off today, because I need to replace the thermostat and I saw that oil is leaking at the bottom, from where the transmission bolts up against the engine. There was also a little oil on the inside of the undercover and on my driveway.

I assume this means the rear main seal is leaking? Perhaps from where the sealant meets the oil pan and not the seal itself, given the design of the seal on my Mazda? (Of course, now I feel stupid for not taking the advice to leave the seal alone. Although the transmission shop mechanic said he's never had a seal come back leaking.)

I don't know that I can deal with taking the car back in right now, because I need to go help my mother and sister out with my father who has been ill. I was going to drive up to where they are (370 miles). Is it a bad idea to drive the car with this leak and wait to deal with it later? Could I get stuck somewhere?
 
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Well, I went ahead and had the mechanic do the rear main seal, when he did the clutch. I got the car back on Wednesday. I was taking the undercover off today, because I need to replace the thermostat and I saw that oil is leaking at the bottom, from where the transmission bolts up against the engine. There was also a little oil on the inside of the undercover and on my driveway.

I assume this means the rear main seal is leaking? Perhaps from where the sealant meets the oil pan and not the seal itself, given the design of the seal on my Mazda? (Of course, now I feel stupid for not taking the advice to leave the seal alone. Although the transmission shop mechanic said he's never had a seal come back leaking.)

I don't know that I can deal with taking the car back in right now, because I need to go help my mother and sister out with my father who has been ill. I was going to drive up to where they are (370 miles). Is it a bad idea to drive the car with this leak and wait to deal with it later? Could I get stuck somewhere?
It really depends on the severity of the leak. Usually it’s not that bad of a leak that you’d ever really need to top off (a naturally occurring rear main seal leak) and you’d be fine ignoring it.

Having just gotten installed though, is it a bad leak? A poor install could be a much worse leak. It could also get oil on your flywheel and clutch which is detrimental to a clutch.

It just boils down to how severe the leak is.
 

cb474

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It really depends on the severity of the leak. Usually it’s not that bad of a leak that you’d ever really need to top off (a naturally occurring rear main seal leak) and you’d be fine ignoring it.

Having just gotten installed though, is it a bad leak? A poor install could be a much worse leak. It could also get oil on your flywheel and clutch which is detrimental to a clutch.

It just boils down to how severe the leak is.
Thanks for the reply.

I think it probably leaked a tablespoon or so. From what I saw on the undercover and the driveway. That between when I picked the car up on Wednesday and today, Saturday.

I cleaned up the oil from the spot where it was leaking and then worked on the thermostat for several hours. It was forming a drip, by the time I was done, just sitting there without the engine running. Then I drove the car around for twenty minutes to check the themostat and when I pulled back into my driverway and looked at the carboard I put under the car, there were already a couple drips of oil on it, right after I parked.

So I don't know if it's a bad leak, but it's not a super slow leak either. And it did not leak at all before.

Yeah, I'm worried about getting oil on the clutch and flywheel. I wonder if the mechanic just forgot to put the silicone sealant, where the seal retainer meets up with the oil pan. He wasn't familiar with this type of rear main seal, when I gave it to him. Although he was the one who looked up and told me about the silicone sealant, when I first talked to him on the phone. And he is a transmission specialist.

I think it definitely has to be repaired. It's not a slow enough leak to tolerate forever. Just of issue if I can wait on it and go on a 700 mile round trip drive first.

I also wonder, when it's redone, If I need to get another new rear main seal.
 
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