www.ColoradoClassicBroncos.com

So Phyler convinced me to use a sleeve and just pull the transmission and replace the rear main that way.

https://tdmotion.com/product/1985-1997- ... epair-kit/

I am really hoping this will resolve my excessive oil leak. If it doesn't-- I guess I can start looking elsewhere.

Also-- for those that saw my earlier post about my bent housing, I took it to Western Drivetrain. I also just had them remove and replace a Set20 bearing on a rear axle.
http://www.axleandgear.com/

I've had good luck using those sleeves. I used one on my old 9" axle and one on my ZF input.

When I was reading on rear main seal leaks, it looks like the flywheel to crankshaft bolts need thread sealant. I'm pretty sure I didn't use it, but it doesn't seem to be leaking. Just something else to make sure of while the transmission is out. I wish I knew that when I had the ZF out to reseal the input shaft. I'll check/add sealant the next time everything is apart.

Gunnibronco wrote:I've had good luck using those sleeves. I used one on my old 9" axle and one on my ZF input.

When I was reading on rear main seal leaks, it looks like the flywheel to crankshaft bolts need thread sealant. I'm pretty sure I didn't use it, but it doesn't seem to be leaking. Just something else to make sure of while the transmission is out. I wish I knew that when I had the ZF out to reseal the input shaft. I'll check/add sealant the next time everything is apart.

So I also was trying to look into whether the crankshaft bolts need a sealant and I came to a different conclusion for the 351W. My understanding is the 302 has open bolt holes and need a rtv type sealant to ensure there is no leak from the bolt holes BUT the 351 holes are closed to the block so there is no possibility for any leak, therefore no sealant needed...

Eck wrote:

Gunnibronco wrote:I've had good luck using those sleeves. I used one on my old 9" axle and one on my ZF input.

When I was reading on rear main seal leaks, it looks like the flywheel to crankshaft bolts need thread sealant. I'm pretty sure I didn't use it, but it doesn't seem to be leaking. Just something else to make sure of while the transmission is out. I wish I knew that when I had the ZF out to reseal the input shaft. I'll check/add sealant the next time everything is apart.

So I also was trying to look into whether the crankshaft bolts need a sealant and I came to a different conclusion for the 351W. My understanding is the 302 has open bolt holes and need a rtv type sealant to ensure there is no leak from the bolt holes BUT the 351 holes are closed to the block so there is no possibility for any leak, therefore no sealant needed...

That makes a lot more sense than holes open to the inside of the motor. Glad it's on your radar.

Sorry for making all these irrelevant posts on your build.

IΓÇÖm rethinking this again!

The spot near the main seal does not appear to be wet (just dirty and some probable blowback from a higher leak).



I had degreased as much of the engine I could get to and drove it home from the car wash. The spots that seem to have the most accumulation of caked oil and wet spots are at the rear side of both valve covers and look to follow that path downwards. I also noticed a slight leak at the dipstick tube and it appeared to be a little loose (so I tightened it).



IΓÇÖm now thinking I need to pull the valve covers and either put in new seals or replace the covers themselves with new seals. I currently have the upgraded blue silicon gaskets on.


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Valve cover vents?

Jesus_man wrote:Valve cover vents?

It does look like a good amount of leakage from the vent on the passenger side. There is no vent on the driver side. It doesnΓÇÖt look like any leaks from the oil fill cap. These were originally carb valve covers that I did some mods to to make work for the EFI.


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I had found my cast valve covers like that to be cracked at the bolt holes.

I am hoping that the real source of my leaks has been 2 main areas:

1. The grommet pictured above. I went ahead and removed the valve covers and ordered new gaskets (although the ones on it looked to be in fine shape). While I had the covers off, I RTV'd the inside of the grommet. It spun freely before and it appeared oil was making its way between the grommet and the valve cover. I also added lock washers to the valve cover bolts.

2. On the other side, once I removed the upper intake, I found that the hose connecting the upper intake to the PCV filter hole in the back of the lower intake had blown completely off the upper intake. I have a feeling that was where a majority of my leaks were coming from. I had been noticing an unusual amount of "backfire" at certain air/fuel/coast/acceleration siuations recently so hopefully this fixes that issue as well. I added a hose clamp to ensure it does not come off again.

In addition, I decided to also change the header gaskets as I felt I was getting some exhaust leaks and also kept having my header bolts loosen up. The gasket I added is suppose to compress up to 50% but will also expand back if needed. It is "guarenteed" to fix exhaust leaks (we will see). I also swapped my header bolts out with some locking bolts that are desgined to NOT loosen up.

Will hopefully have it all back together tomorrow with an oil change and can see if I was successful in diagnosing the major points of leaking. Between the PCV hose not attached to the upper intake, the dipstick tube loose, and the grommet on the other valve cover now sealed-- I am really hoping this captured most of it!!

Hoping for the best!! Remember, with a bronco, you needn't worry until the leaking stops! LOL!

Seems like all of that would at least help. Fingers crossed.

These valve covers are clearly the source of my leak. The passenger side is by far the worst but the driver side is leaking a little bit too. I think there is a chance they are leaking at the volt holes as they looked to be a little wallowed out.

A junkyard run to grab some stock explorer covers might be in my near future.

IΓÇÖve read a little bit on aftermarket covers having issues with roller heads.

Any wise words of wisdom? ItΓÇÖs a 351w with GT40 heads, roller rockers, explorer upper intake and EFI.




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stamped steel factory valve covers may not be tall enough to clear roller rockers

I got a little trigger happy and ordered a set of these:

https://lmr.com/item/SVE-6582B/1986-199 ... f4548ac0f1


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I have the mustang covers on mine. (not the fancy polished ones) no leaks at all.