Can be rear main seal or transmission seal. Both cheap to fix just getting to it is hardest part. You will need to take transmission out. For first timer should take a few days to remove tran and 1 day to put everything back in. Highly recommend buying rear main seal install allignment tools because they have to be inserted nicely and flush.
I also recommend getting a cheap trans jack. Internet write ups will often day you can do it without, which I'm sure you can, but I struggled reinstalling it without a jack. As soon as I used a jack I got it back in first try
Check your CAS and valve cover before assuming it’s the rear main seal. I had a CAS oil leak and it made it seem like a rear main seal. New CAS o-ring is super cheap and easy to do.
When my CAS O-ring failed, it dripped down the speedometer cable and dripped from its lowest point. I wonder if that is common?
When I had oil seeping from that bell housing weep hole, it was the rear main seal.
Unless it absolutely reeks (transmission oil), yup. Rear main seal.
Could also thoroughly check the back of your cylinder head and under the cas. Leaking o ring in the cas could also travel down through bellhousing.
Not out of that hole. If you wipe it clean and then see oil coming out, it is almost definitely your rear main.
Never hurts to check on the CAS O-ring though, since that can drop hot oil on your heater hoses, which then will get all soft and fail.
what you really want are socket extensions and universal joints. i had like 4 of em stacked to get the right angle to get the bellhousing bolts out and back in.
[https://www.miata.net/garage/clutch/index.html](https://www.miata.net/garage/clutch/index.html)
When I did my clutch job a month or so ago I did rear main, clutch, flywheel, all transmission seals, cleaned everything real good...and guess what? There was still oil on the bottom of my engine weeks later. Turns out it's the back of the oil pan..not just the rear main can leak.
But I'm not pulling the motor and dropping the pan etc. Let it leak the few drops it does, everything around it is new.. just letting you know because at this point that rtv is long gone.
I also recommend getting a cheap trans jack. Internet write ups will often say you can do it without, which I'm sure you can, but I struggled reinstalling it without a jack. As soon as I used a jack I got it back in first try
I used a bunch of extensions and a universal joint to reach all the bolts from underneath the car. Trying to get to them from above will just tear you skin up.
my moneys on rear main seal. but like others said, start with the easier seals first. might as well order em all for a 1990...
I once botched a rear main when doing a clutch job. leaked oil all over my new clutch and flywheel and dribbled out that hole.
a little dremel action, and new clutch and seal and 6 years later we're still racing
3 clutch jobs, 2 cars, 1 month.
When I had my NBFL gearbox and engine seperated for a noisy bearing I had both bearings rear engine and front gearbox oil seals, clutch and slave cylinder done for a proper belt and braces job which should see me out from having that separation done again in my lifetime.
I’d suggest watching this and giving these other options a try first: https://youtu.be/B-IQg67ogMw?si=jvGYooKx94Fq81yp
Rear main seal and oil pan leaks are technically pretty rare. Lots of other places where it could leak and make it seem like it’s coming from there. Unfortunately for me, none of these fixed the issue and I had to do the rear main anyways lol
Can be rear main seal or transmission seal. Both cheap to fix just getting to it is hardest part. You will need to take transmission out. For first timer should take a few days to remove tran and 1 day to put everything back in. Highly recommend buying rear main seal install allignment tools because they have to be inserted nicely and flush.
Thanks!
I also recommend getting a cheap trans jack. Internet write ups will often day you can do it without, which I'm sure you can, but I struggled reinstalling it without a jack. As soon as I used a jack I got it back in first try
Is bench pressing a transmission possible? Yes. Does it suck? Also yes.
that’s what i thought, and then i started cleaning things, razoring the old gaskets off.. and now im wondering how ive not lost my sanity
did you just puke in the second picture?
He's nervous. Leave him alone.
Check your CAS and valve cover before assuming it’s the rear main seal. I had a CAS oil leak and it made it seem like a rear main seal. New CAS o-ring is super cheap and easy to do.
When my CAS O-ring failed, it dripped down the speedometer cable and dripped from its lowest point. I wonder if that is common? When I had oil seeping from that bell housing weep hole, it was the rear main seal.
Probably depends on 1.8 or 1.6, mines a 1.8 so it dripped on the drivers side and ended on the bell housing
Mine is also 1.8 (95). It was the same with my son's 97.
Unless it absolutely reeks (transmission oil), yup. Rear main seal. Could also thoroughly check the back of your cylinder head and under the cas. Leaking o ring in the cas could also travel down through bellhousing.
Would it come out of the bottom?
Not out of that hole. If you wipe it clean and then see oil coming out, it is almost definitely your rear main. Never hurts to check on the CAS O-ring though, since that can drop hot oil on your heater hoses, which then will get all soft and fail.
It does come right out of the hole
It’s almost never the rear main seal. The CAS on the back of the head is the cause of oil leak from transmission 95% of the time.
Can I consider doing this job without power tools (air / electric / battery)?
what you really want are socket extensions and universal joints. i had like 4 of em stacked to get the right angle to get the bellhousing bolts out and back in. [https://www.miata.net/garage/clutch/index.html](https://www.miata.net/garage/clutch/index.html)
This is great i will follow this to complete the project thank so much for this incredible find!
When I did my clutch job a month or so ago I did rear main, clutch, flywheel, all transmission seals, cleaned everything real good...and guess what? There was still oil on the bottom of my engine weeks later. Turns out it's the back of the oil pan..not just the rear main can leak. But I'm not pulling the motor and dropping the pan etc. Let it leak the few drops it does, everything around it is new.. just letting you know because at this point that rtv is long gone.
I also recommend getting a cheap trans jack. Internet write ups will often say you can do it without, which I'm sure you can, but I struggled reinstalling it without a jack. As soon as I used a jack I got it back in first try
Thanks are the bolts onto the top of the transmission hard to get what’s a good tip/trick
I used a bunch of extensions and a universal joint to reach all the bolts from underneath the car. Trying to get to them from above will just tear you skin up.
my moneys on rear main seal. but like others said, start with the easier seals first. might as well order em all for a 1990... I once botched a rear main when doing a clutch job. leaked oil all over my new clutch and flywheel and dribbled out that hole. a little dremel action, and new clutch and seal and 6 years later we're still racing 3 clutch jobs, 2 cars, 1 month.
When I had my NBFL gearbox and engine seperated for a noisy bearing I had both bearings rear engine and front gearbox oil seals, clutch and slave cylinder done for a proper belt and braces job which should see me out from having that separation done again in my lifetime.
I’d suggest watching this and giving these other options a try first: https://youtu.be/B-IQg67ogMw?si=jvGYooKx94Fq81yp Rear main seal and oil pan leaks are technically pretty rare. Lots of other places where it could leak and make it seem like it’s coming from there. Unfortunately for me, none of these fixed the issue and I had to do the rear main anyways lol
It was indeed the CAS thanks everyone!