The Stovebolt Site Forums The Shop Area Engine Shop Leaks from both sides

Hello- I've got oil leaks coming from both the front and rear ends of my 54's 235 engine block. From what I've read by searching, It seems there are three places that I can try to fix: 1) Pan gasket, 2) Rear (rope) seal, and 3) Front crank seal. I know there is no oil coming from the top of the engine or the oil filter fittings, so are the 3 items above the only possibilities?

Secondly, when replacing the front seal, is it necessary to remove the front grill and radiator? I'm assuming so since you have to take off the crank pulley?

Finally, I've only seen a few places that sell the front seal. Is this part not commonly replaced? I guess my real question is, how likely is it that the front seal is leaking? Perhaps the real question is, "why is oil getting past the seals?". I'm guessing the rear rope seal is just old and bad. But if the front seal is passing oil as well, does this indicate a pressurized bottom end, perhaps related to a clogged draft tube or similar problem?

I'm hoping to button her all up over the winter so I can avoid those unsightly stains in the summer! Thanks for your help.

Both seals will be included in an overhaul gasket set from FelPro or others. They are likely just old and worn out. Remember that the rubber used 53 years ago was not as good as todays seals. The rope seals are famous for leaks. Your engine is the full pressure 235 and was first year for that but that doesn't explain the leaks or all old GMC's would be leaking for that reason alone. Also w/o the full filter of modern engines there was a lot of dirt and contaminents in the oil to increase the wear factor on the seals. At least that is my theory and it explains it to me so I'm stickin' to it.

This harmonic balancer repair sleeve might be useful.

If you have cleaned off the oil and grime, you should be able to tell an oil pan leak from a rear seal leak. The rear seal leak is almost a 100% possibility. An oil pan leak is a lower possibility but not uncommon.

There is an old adage that goes "if the old truck is not dripping a little lubricant, it needs lubricant".

Regarding the road draft tube being plugged. This is easily removed and checked/cleaned.

Tim

Tim, that old adage goes for old Harleys too. My old FLP marked her spot pretty regularly.

Just a couple things........I'd pop the oil filler cap and watch for some huffing and puffing....might be more crankcase pressure than your draft tube can handle. It could/would indicate worn rings or valve guides and new seals wouldn't do much good. If you don't have excessive blowby, it would be time to go after the seals. Unfortunately, the fixes for the rear main seal and the timing cover seal are not something you crank out in a couple hours.

Yes, the radiator does need to come out to pull the balancer, the repair sleeve recommended by Tim is a lifesaver. I've always pulled the timing cover, replaced the gasket and seal and seated the H/B with the cover loose. This insures that the new seal will center on the improved sleeve on the balancer. The down side of this, is that to get the timing cover off, you'll have to drop the pan to get the 2 bottom timing cover bolts that are installed from the inside. While I'm in there, I like to drop the front main cap, tap it with 3/8 threads, drill out the (2) 5/16" bottom timing cover bolt holes so I can install the bolts from the front. With the pan off, you can wrestle with the rope seal. That is in itself, is another whole kettle of fish!!!

If by chance, you have excessive blowby, you may need to take a closer look at the compression and oil pressure and the general overall condition of the engine. Nobody welcomes the need for a rebuild but replacing the seals on an engine with questionable oil pressure, excessive blowby and leaks might just be putting a band-aide on a more serious problem. Hopefully, you can avoid that situation but you've got the winter months to get things squared away. I hope this helps.

Dave

Dave-

I don't understand what you were saying about the blowby. If I understand your logic, you are saying that huffing and puffing from the filler cap area (top end) would indicate excessive pressure in the crankcase that is passing by the ring(s), and perhaps also pushing the oil past the worn seals. Assuming my draft tube is clear of debris, how would it be possible to have "excessive" crankcase pressure to the point that the draft tube couldn't handle it? My engine is stock.

Also, thanks for the tips regarding the timing cover. I've seen that idea before (perhaps on your webpages) and it seem like it makes things easier. I'll probably keep mine unmodified, though but your writeup gives me a good idea of what I'm in in for. Can you get the H/B off with just the radiator removed, or do you have to remove the front grille as well?

Thanks. Greg

If you have no fumes coming out of the draft tube when it is idling then the tube is most likely plugged. This can cause some pressure buildup inside the pan and I would imagine it would encourage leaks.

Hi Greg,

The fact that your engine is "stock" is not going to exclude it from having blowby. You didn't mention much about your engines condition other than the leaks. That's why I suggested popping the filler cap and seeing if there is huffing and puffing when you rev the engine. If there was, pop out the draft tube (one bolt on clamp, rubber mallet) and verify it's clear. If there wasn't, you don't have excessive crankcase pressure. This would indicate that your leaks were just from the seals and not being pushed out under pressure.

On a 54 truck it's just as easy to pop off the bumper, grill and radiator. I've done it both ways and it's much easier to R & R the H/B and timing cover with clear access over the front cross member. I've also just replaced the seal without loosening the cover and had the new seal weep oil. Never again! You're going to have the pan off to change the rear seal so you might as well do the timing seal corrrectly, even if you don't modify the front main cap.

While you've got the timing cover and pan off the block, you need to inspect the sealing surfaces and make sure they are flat. Most have been torqued and overtorqued and need some straightening. Once you've got a good flat surface, a SPARING bead of RVT on the pan rim will hold the gasket in place. Let it set up a couple hours with clothes pins to hold it in place. I like to use a dab of #2 Permatex on the timing cover and pan bolt threads. Don't overtorque initially as the gasket will soften. In a couple weeks you'll want to give them another little nudge. Paying a little extra attention to detail will pay off with a clean, dry garage floor.

You asked about the seals....I'd try NAPA....they've been a good source for engine parts.

I'd like to apologize in advance for using the term "easy and easier" in describing the replacement of the timing cover seal. Pulling all the sheet metal is a real pain-in-the-neck ....it's like having a root canal...but once it's done and done right, you won't have to worry about it again! But it's the price we have to pay to keep our "old iron" running.

Dave

Dave-

What you said about the blowby makes sense, and I'll pop off the filler cap and have a good listen next time I start her up. The engine seems to run pretty strong, so I'll be really surprised if I hear any huffing and puffing. Although my engine has only 40K miles on it, I'm sure the seals are probably in need or replacement. Plus it should make for a fun evening or two out in the garage.

I have small kids and I have a hard time blocking out time to work on the truck, but this seal business is something I should be able to do without asking my wife to watch the kids for too long..

Thanks!

From my experience, looking at a big job like pulling the pan to replace seals etc. is a little overwhelming. However, taking it in small steps and with enough time turns it into a bunch of smaller rewarding sub steps. I say this from a perspective of having done a whole truck over five years while having a full time job and raising a family. I found that I was able to admire the accomplishment of each step and plan in my head the next one. I did not have a schedule and I did not respond to the question "how long will it take? " from friends.

I know exactly whay you mean about small steps. I have friends that tell me that it doesn't make sense to fix this or that because you'll end up having to do it all over again (and buy new seals, rubber, etc.) when you get around to restoring it from the ground up. Whatever! I just want to get everything in safe working condition and drive it as such until I have more spare time to "restore" the truck.

So I've been thinking about this seal replacement job.. It seems like once I take the pan off I'm pretty much committed to doing the whole job. I can't get at the front or rear seal without the pan off. So what do you think is a reasonable expectation for replacing all the seals--4 hours?

The other thing I realized after reviewing my shop manual is that I can only replace the bottom half of the rear main rope seal. It says I'd have to take the whole engine out in order to remove the crank and replace the upper portion of the seal. I guess I just have to hope that the bottom portion of the seal is where it is leaking.

Also, with regard to the front seal, I'm not clear as to where the seal is. The book indicates that there is a leather seal mounted inside the timing cover. Isn't there another seal in there as well, which is why that speedi-sleeve is used? I'm also not sure if you have to take off any of the timing gears in order to replace the seal. (Sorry for the newbie type questions--I haven't had a change to get in there and see what it looks like yet).

Greg,

It has been about 30 years since I did these operations as repairs (more recently, I've done these operations during a rebuild/restore). My memory is often lacking, so let's hope someone with more recent experience will answer.

1. Yes, doing any one job puts you in a position to do the other jobs - might as well.

2. The trickiest job would be the rear seal, but it is worth a try - just doing the bottom, even.

3. The speedi-sleeve goes over the front of the end of the driveshaft (it "repairs" grooves in the driveshaft by giving a smooth surface for the seal that is mounted in the cover). I am pretty certain this can be installed without removing any timing gears.

4. 4 hours - if you are good and if you are lucky that everything comes off and goes on "by the book". Also, there is some sort of glue/cement that comes with the speedi-sleeve (I think) and this might have to cure.

Tim

The upper rear seal can be replaced without dropping the crank. There is a procedure for doing this in the Tech Tips section of this sight. When I replaced my seals I bought an upper oil seal remover tool from Autozone. It cost $3.00 and made the job easier. I chose to use the neoprene seal instead of the older type of rope seal. For me the upper seal rolled in place quite easily and I have no leaks.

I have never messed with the rope seal, but hear about what it takes o install one sounds like a pain. I have replaced them wiht the neoprene twice. Once in the vehicle and once during the engine rebuild. With the neoprene it is so easy. I think I messed up on mine the last time though because I have leaks from both sides!

Jim- Thanks for pointing out the tech tip. I wonder if there are any "gotchas" to dropping the crank as described in the tech tip? Also, does the tool you referred to look something like this tool? I wonder if I'd even have to drop the crank when using a tool like this to re-install the new seal?

I'm also still a bit mystified about this front seal business, but I think I'm getting it. I found this picture as well as this one. So I think the seal goes in the timing cover surrounding the cover's hole so that when you insert the H/B back on to the crankshaft, the seal mates up with the small shaft/stud that is part of the H/B. Is that right? And also the timing cover is filled with oil during engine operation to lubricate the timing gears?

I'm sure all of this is clear as day when you get in there, but I want to make sure I have a decently clear picture of what I'm going to do before I start taking stuff apart. Thanks.

That is the tool for replaceing rear main seals.

A couple things to check out. The ultra thin speedi-sleeve that I originally mentioned, slides over the seal end of the Harmonic balancer and is glued on with an epoxy adhesive. It gives you a perfectly smooth surface for the new timing cover seal. By having the timing cover loose, when you install the H/B, the seal centers properly on the quick sleeve.

You can pull the cover, straighten out any distorted surfaces, install a new seal and gasket, mount the cover loosley, oil the sleeve and carefully install the H/B, working the seal onto the new sealing surface. Once the seal is started (centered) on the H/B, tighten down the timing cover bolts. It's a good time to visually check out your timing gears but they don't need any R&R unless there is an issue.

Secondly, my machinist dressed my crank during the rebuild to accept the neoprene seal. He felt a rope seal would do a better job of sealing on a crank that has been running a rope seal and has not been dressed. Someone else might be able to expand on this.

Dave

The tool I got was Autozone part number 27147. It is usually stocked at the store and like I said only $3.00. I didn't need to drop the crank at all when I replaced the seal. After pulling out the old rope seal I pulled a couple of gun cleaning patches thru to clean things up. By pushing on the seal while turning the crank the new seal rolled right in. I used the neoprene seal out of personal preference. It was in stock and I bought it over the counter. One caution when using the neoprene seal is to keep the ends clean and oil free during installation. The ends have glue on them and when you put the bottom cap on the surfaces of the seal ends bond together.

Relax!! It's not that big a job. This is just from my experience with my truck over the past 12 months, but before I decided to pull the engine(the second time)and actually have it rebuilt the way it should have been done,(trying to avoid spending the bucks) I replaced all the seals you are talking about.And even with me being as slow as I am, managed to get it all taken care of in about 4 hours. I didn't take off the grill, but did have the radiator out of the way, and with a good puller didn't lose any more than usual off my knuckles. Loosened the motor mounts and jacked up the engine with a cherry picker just enough to get the pan off and replaced all the seals, checked the oil pump, replaced the pan gasket, and installed a new HB. And had a blast out in the garage(with a 4 year old grandson wanting to help). Gave him a junk lawn mower engine and a couple of wrenches and told him it was broke and he had to fix it. Took a while to scrub the grease off of him later that nite, but you should have been there to hear the conversation over supper. These old trucks are very forgiving, and it's best if you try to think of any troubles you are having as having the simplest solutions. It's ususally something simple that gets it taken care of.
Tramp

I replaced my rear main on my 51 when I rebuilt the motor. As an experiment I tried removing the upper half as per the tech hint. The upper half would not budge. It was only after lowering the crank was it possible to remove the upper half. These results are different for many cases. The one thing is that if the seal gets damaged and it won't come out you then have to lower the crank.

Adjusting the shims in the rear main can help some with the leak problem. This was standard procedure in the days that these trucks were serviced.

The neoprene seal is not deemed appropriate for the early sixes. I believe this changed somewhere in the late fifties. The reason is the machining in the block cavity is not precise enough for the neoprene seal.