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TR4/4A And the fun continues...rear main leak


Jedi Trainee
Well, the car is drive-able and I got it all dialed in after my initial startup that realllllly overheated the engine. But, it seems to idle OK and I used a Colortune to get A/F closer and Air Flow Meter to set the idle. However, after the last drive I noticed oil on the ground. At first I thought it might be the lower blow off, but then today I took off the lower transmission cover/plate. Well....it's covered in oil. I started the car again and let it idle after cleaning up all the oil I could see. Looks like it is coming from behind the flywheel which in my mind...Rear Main Seal. Noooooo!!!!! I put a Viton kit from TRF (the one where you don't grind the crank) and I was VERY confident it was put in right and it had plenty of time to set as I didn't start the engine for quite some time. Maybe overheating the engine quite well (due to running lean) caused it to start leaking? But I drove it twice before it started leaking. I honestly don't have the time, energy or space to deal with this. It's leaking pretty good once the car warms up. It's not a slow drip, it drips every 4-5sec. Nice fresh Driven break in oil! But...at least the car looks good! Just won't have the tranny tunnel cover ever in, or carpet, or seats since it's going into storage come mid-May.

Anyone have any other thoughts? Pretty bummed right now. And to top it off, for some reason my 4Runner's battery is being drained and the 3rd member I just got gears and an air locker put in won't fit back in the diff case. Going to have to grind a little away. Two projects at once isn't the smartest thing.


Jedi Knight
Country flag
Although the rear seal is likely the problem there is another source of oil at the back of the block. That is the plug or cap found at the rear of the cam. Lots of oil goes past that spot as it is the feed to the valves / lifters. You still have to pull the tranny and then the flywheel to be able to see the plug.


Country flag
Don't give up, make sure you have adequate crankcase ventilation. I have seen this happen with freshly built engines and new seals. I don't remember off hand what a TR4 engine has for ventilation, draft tube or maybe some tubes on the carbs. Anyway, engines create pressure in the crankcase. Unless it is properly vented it will try to relieve the pressure everywhere, including the seals. Randall and others may have some better ideas how to vent the TR 4 cylinder, there have also been discussions you should be able to find with a search of the archives here.


Jedi Trainee
Well, I know there is the lower vent pipe off the passenger side block and the cap on the rocker. It is possible it could be coming out of that plug as they replaced it while rebuilding the heads. Unfortunately I just don't have the time to rip it all out as I'm losing my shop space shortly and would rather drive it home real quick to store it. And I only have a one car garage so trying to do this in a small space would not be fun. But at the least it looks like I'm pulling the transmission. Yay! :smile:


Luke Skywalker
Country flag
I have a leak too, after so carefully installing that Viton seal. I'm not sure where I went wrong but there are two areas where I suspect: a) the instructions mention using a silicone sealant I believe where the seal fits tightly in the grove of the outer ring, and I suspect I was too light on the sealant; and b) I might have not been careful enough tapping the aluminum rings around the centering hub to be sure the alignment was perfect. I remember wondering how you really know it was tapped closer and better than before the tapping.
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