Do all old trucks leak or is there an acceptable amount?
 

I might catch hell for this post or topic phrasing but when I was looking for a truck a few people told me these old trucks all leak. I kind of thought it was just then trying to justify their trucks leaking but now IDK?

The mechanic I had look at my truck said there are a few small leaks, the valve cover, a small area by the trans and the main seal. He said he isn't a big fan of chasing small leaks on older vehicles and just keep an eye out and keep em filled.

Any leak mitigation experts here, can these trucks be fixed 100 percent and what am I looking at in trying to do so. Are there thicker modern gaskets that will work better, is it worth the effort. Is there any reason these should keep leaking after proper repair?

I could easily tackle the valve cover myself and I have read about the main seal and that it can be done by removing the pan.

Re: Do all old trucks leak or is there an acceptable amount?
 

Even restorations leak:lol: my rebuilt by reputable steering box leaked the day my truck started. It was really bad for a while too. I may be lucky actually, switched from ACDelco Type 3 to Valvoline Type 3, and so far, knock on wood.

My transmission leaks a pinch, likely where the dipstick tube inserts.

Unless it's a gasket, valve covers leak because they've been distorted. Too tight and uneven.

Throw some full synthetic in old assemblies you'll find leaks you didn't know you had. It happens, old drivetrains leak oil and trans fluid, and if they don't fantastic.

Re: Do all old trucks leak or is there an acceptable amount?
 

I am in IT now of course and I live in a 1 or 0 world where something usually works right or it doesn't and it really doesn't help that I am OCD about a lot of things. I guess I need to realize the truck is almost as old as me and I will probably leak some places too someday.

Re: Do all old trucks leak or is there an acceptable amount?
 

Yeah I was in IS 15 years, my job required lots of research, and every detail accounted for. Turned me into a vegetable. No leaks yet.

It's CDO man, OCD is out of order.;)

Re: Do all old trucks leak or is there an acceptable amount?
 

I don't want to draw Mr. Murphy's attention by responding to this thread...:hh:

Re: Do all old trucks leak or is there an acceptable amount?
 

It takes effort to truly dry them up. Chevy went to center bolts in the valve covers, for example. That reduces the distortion from having bolts around the perimeter. They started using RTV in the '70s, and that helps a lot. I think I saw you have chrome sheet metal valve covers? If I ever do anything with my truck's engine, I'll go to billet aluminum to reduce valve cover leakage. Besides, they look :cool: . It doesn't actually leak that badly. It mostly burns it, I guess, because I don't see drops or puddles under it, just a little seepage.

Re: Do all old trucks leak or is there an acceptable amount?
 

My 71 C/20 307 has no leaks engine wise. The heads have never been off. I did recently replace both valve cover gaskets (cork) because they were original and rock hard. Even the rear main seal doesn’t leak.

Re: Do all old trucks leak or is there an acceptable amount?
 

I find most will accept small leaks. The reality is that back in the day these trucks did not leak and with some effort can be made to once again not leak. Your level of commitment will determine your acceptable threshold. Mine is zero leaks and I am at that state. I want to be able to park anywhere without concern.

Re: Do all old trucks leak or is there an acceptable amount?
 

Mine does leak transmission oil. "I'm just marking my territory", like an old Harley which a chain oiler. ;) I'm going to fix it one of these days. It's actually pretty annoying having to put a quart of ATF in it every 6 months, or so.

Re: Do all old trucks leak or is there an acceptable amount?
 

Hmmm, I was an electrical engineer and my software worked fine until IT would update the system. So much for 1's and 0's... Mistakes are as prevalent in IT as leaks are in old trucks, it's just something that has to be fixed.

Good luck, Rg

Re: Do all old trucks leak or is there an acceptable amount?
 

LOL, love ya man

Re: Do all old trucks leak or is there an acceptable amount?
 

No, they don't need to leak.

For valve covers, use Permatex to stick the gasket to the cover, then DON'T OVERTIGHTEN and use the stock spreaders under the bolts.

The main seals are going to get worse at some point, but there's no halfway measure to fix them.

Kinda the same with transmissions if it's not the pan.

Diff leaks are usually covers that aren't flat at the gasket surface.

So...for gaskets, they don't have to leak. for seals..."it depends" :)

Re: Do all old trucks leak or is there an acceptable amount?
 

Yeap, you should!

Re: Do all old trucks leak or is there an acceptable amount?
 

My philosophy is that as long as it's leaking a little, all is well. When it stops leaking it's time to worry.
Fill it back up with the necessary fluids and go again. :lol:

Re: Do all old trucks leak or is there an acceptable amount?
 

I am probably going to put some UV leak detect in it and try to verify where it is coming from.

Can the rear main seal be completed by just taking the oil pan off and removing the 4 bolts to slip the new seal in.

Re: Do all old trucks leak or is there an acceptable amount?
 

I have done it that way, there's a tool to help with that.

Re: Do all old trucks leak or is there an acceptable amount?
 

Rear main seals can be a problem on pre-Vortex engines as the original rope seals had asbestos in them and we all know that's verboten these days. If you need to replace one the best ones are made by Best Gasket, their grafite rope seals.

That being said poorly fitting oil pans contribute to many suspected rear main seal leaks.

Replacement of the rear main seal can be done without removing the engine but you will need to loosen all of the main caps to drop the crankshaft down so you can get ALL of the old seal removed and get the new seal properly seated and cut to size once seated. There's folks who say you can pull the new seal in with the old seal by tieing them together with fishing line but I've never made that work. Personally I would rather pull the engine to replace the main seal. It also makes checking the oil pan fitment easier.

Re: Do all old trucks leak or is there an acceptable amount?
 

I resealed my engine and transmission when I bought my truck. Not a drop of oil came out for about a whole week of it being back together :lol:. My fluid is never low when I check but I see small spots under the truck where I keep it. I think it's just the nature of the beast. Fix what you would like and ignore the ones you don't:lol:.

Re: Do all old trucks leak or is there an acceptable amount?
 

I remember the old Jaguar Owners' Club joke about if your Jag leaks, that's good. When it stops leaking, check the oil and add a few quarts.

Re: Do all old trucks leak or is there an acceptable amount?
 

That's why you save cardboard boxes... To catch the drips ;)

I've had a 98 wrangler for almost 15 years, so I know about leaks.
It actually is completely leak free though! You have to go through and fix each one.

Avoid synthetics. Older vehicles/seals don't like them.

My new(old) truck, also leaks a tiny bit. I fixed the rear wheel cylinder so there's one done.

The gearbox drips though slightly.

Re: Do all old trucks leak or is there an acceptable amount?
 

I need to get some puppy pads made for shop floors.

Are the stop leak additives all snake oil and bad for the motor or are there ones that actually work or slow it down. I quit drinking beer somewhat lol so I guess I will have hard lemonade while in the drive replacing gaskets. I wonder if I could use RTV like caulk- joking

Re: Do all old trucks leak or is there an acceptable amount?
 

I would not put any stop leak stuff into a cooling system or engine oil.

I have used it on power steering systems though (no filters, no small channels etc. I've had success with the Lucas stuff on more than 1 vehicle.

Re: Do all old trucks leak or is there an acceptable amount?
 

My rebuilt 350 in my 72 does have some leaks. Have owned it for about 3 months now and she sits for 3-4 days, then driven on the weekend. Oil was full and now at 3 months I was down about a quart and nearly a half this evening.

I'm not too worried as I'll keep an eye on it. The diff leaked but that was not a bad fix. Sm465 not leaking anywhere so another bonus.

Re: Do all old trucks leak or is there an acceptable amount?
 

The old design engines leak. In my opinion the engine leaking more than a quarter coin size spot or two on the floor after driving it is excessive, and less than that will be difficult to eliminate, and that is why your mechanic said he didn't favor chasing small leaks and just keep an eye out for it becoming more. I did reduce my engine leaks with new reuseable rubber valve cover gaskets, and studs and valve cover hold down spreader bars.

I was spreading a shovel's worth of kitty litter under the engine in my parking spot in the garage, and then recently I went to Lowe's and got a clothes washer pan from their appliance section.

If other components leak you can fix it so it doesn't leak at all using new seals and gaskets, such as differential cover, axle seals, power steering gear, transmission. Those things don't leak when in good repair. I had my power steering gear leaking more than the engine and it drove me crazy so I looked here on the forum and member Tx Firefighter had posted a step-by-step to replacing the seals. It was excellent and the seals cost me $20 or so and I did it.

Back to the engine, I asked the machinist who rebuilt my engine what oil weight I should use when I change the oil, and he showed me a jug of Walmart 20W50 oil and I made a note, and started using 20W50. One time I was in the store and couldn't remember what oil to get and I figured oil is oil and I thought I would just try 10W30. Boy did my engine make a huge mess out of my parking spot. It leaked A LOT. I found my note and changed the oil again to 20W50 and back to just a few drops of leakage.

Re: Do all old trucks leak or is there an acceptable amount?
 

Wait! What? BBC use a rope seal? I thought they use a 2 piece rubber seal same as SBC. Tell me I'm wrong & I'll shut up. I've never had a big block.

Re: Do all old trucks leak or is there an acceptable amount?
 

My stuff leaks so bad - I opened the car trailer up where my chevelle was sitting and there was motor oil, trans fluid, rear gear lube and brake fluid all flowing down the floor.

Basically: if it had liquid in it - it was leaking.

My stuff leaks so bad - I drained all the oil out of my Farmall and it was still leaking.

K

Re: Do all old trucks leak or is there an acceptable amount?
 

I have replaced some gaskets on the Blazer, but the engine really has never been opened up beyond the valve covers. It sat for most of 25 years, so the rear main does seep a little, and I used Z Rod AMSOIL in everything old.

Re: Do all old trucks leak or is there an acceptable amount?
 

Now I am on a mission and it is a challenge to see if I can get it leak free. I look try to look at everything logically and if the surfaces are good, clean and the gaskets are quality and it is all put back and assembled correctly then it should not be leaking. At least the gaskets and even new pans aren't too expensive for me to try. I am wanting a trans pan with a drain plug in it now too.

When I was looking at trucks almost every ad said leak free but then I would see pics of carboard underneath and the seller would say oh, it does do a drop now and then, uh huh

I am hoping the new silicone type gaskets from fel-pro are nice and work well. I had a buddy who didn't believe in gaskets and just used RTV everywhere.

Re: Do all old trucks leak or is there an acceptable amount?
 

I don't know if this is true or not. But back in the day, early 80's. Ok don't laugh. :lol: I was going to wash my engine off at the local car wash and my dad said don't do it because it would cause it to leak. I told him it was already leaking and that's why it was so dirty. He said the old cork style gaskets were designed to seeped oil and attract dirt which helped seal up the engine. It sounded right at the time unless you have a massive leak.

Re: Do all old trucks leak or is there an acceptable amount?
 

Whoops my bad I forgot he had a BBC. Disregard my post. I've been wrapped up in fighting my own leaks.

Re: Do all old trucks leak or is there an acceptable amount?
 

I'm here to piss all of you off lol: I inherited a 1967 C50 dump truck with a bill of sale from 1980 stating a mileage count of 217k miles at time of sale. The bottom of the engine is filthy like it has never been cleaned but none of the crud is wet with oil, it's all dry, the engine burns a quart of oil every 50 miles or so, sounds bad and really needs a rebuild.
This truck is used once every 2-3 months ans started once a month or so.
It sits static most of the time and is parked in the same spot when done being used.
The trans leaks.

Zero leaks from ANY point of the engine whatsoever.
How in Gods green earth does this happen lol

Old pic is from 1990 when it was given to dad as a "gift".
New pic is last year. Good truck.:chevy:

Re: Do all old trucks leak or is there an acceptable amount?
 

While I was in the Army, we had a Category system to identify “Leaks”.
Cat 1: can be seen but only produces at the touch (slight weeping, very minor)
Cat 2: produces fluid but only dripping (not catastrophic with monitoring)
Cat 3: produces fluid in a steady stream (will lead to failure from loss of fluid).
Many of our trucks leak a little becuse the friction seals are over 50+ years old.
Most leak because the seal contracts faster that the shaft/bearing at shutdown
If you have OCD, you might not want and old vehicle.
My 70 has three minor leaks, that know need to be addressed, (oil pan, trans pan, and power steering box) but I just haven’t yet made the time to change out the faulty gaskets/seal. I do have the new parts on the shelf though :smoke:

Re: Do all old trucks leak or is there an acceptable amount?
 

This thread made me laugh… mostly at the 350 in my K20 that pushes oil mist out the pcv breather because it’s wore out, it then blows all over the right side of the engine. It’s got the felpro silicone oil pan gasket and new timing cover and rear main gaskets, as well as the felpro silicone valve cover gaskets. It doesn’t really leak any where in any of those places. It also pushes oil out the front china wall but not because of bad gaskets… somedays it’s as good of an air compressor from the bottom end as it is an air pump for powering in the truck if you know what I mean lol. One of these days I’ll get the 6.0 built:lol:

It actually still runs pretty good all things considered, doesn’t foul plugs etc, but there is a really nice .030 or so lip at the top of the cylinders…

Re: Do all old trucks leak or is there an acceptable amount?
 

This is a brand new Blue Print create engine. As you can see, both ends of the valve cover gasket creeped inward. This on the lower edge of cover and would have surely leaked. Hope the internals were better assembled.

Re: Do all old trucks leak or is there an acceptable amount?
 

Are the fel-pro blue silicone gaskets gtg?

Re: Do all old trucks leak or is there an acceptable amount?
 

Yes, they really do not require any RTV, I use this with the blue rubber gaskets.

https://www.gasgacinch.com/

For all other gaskets I use this.

https://www.permatex.com/products/ga...et-maker-3-oz/

My truck likes to leave its mark when parked, so I have one of these under it.

https://www.autozone.com/shop-and-ga...ray/475418_0_0

Re: Do all old trucks leak or is there an acceptable amount?
 

They work pretty good. On the oil pan They recommend silicone across the timing cover and into the front corners. In the rear I believe it’s the same, across the rear lip of the pan and into the corners. I like to put a few very small dabs in the corners of the valve covers as well.

Re: Do all old trucks leak or is there an acceptable amount?
 

I've used a bunch of felpro gaskets on my Jeep. All good.

Another thing I like are the Lube Locker differential gaskets. They are reusable.

Re: Do all old trucks leak or is there an acceptable amount?
 

Some time ago I had a restricted PVC hose on the WMB. Once I replaced the collapsed hose my oil leakage was noticeably reduced.

Re: Do all old trucks leak or is there an acceptable amount?
 

Yes very good if installed correctly. Like a oil filter gasket, a film of oil is good to help squish and also assist release upon replacement. If using on a pan, timing cover or intake, be sure to dab a bit of RTV in the appropriate corners. No gasket will seal those areas. Last point is the front and rear arch of the oil pans. I found them not to be very snug on the 2 pans I attempted to use. I gave up on finding a good fitting reasonably priced pan. A liberal bead of RTV has held well. Last on your statement of using RTV like calk. I did so on a weep of oil in the arch area between pan and timing cover with success. Cleaned with brake cleaner, and run a bead. Smear and crossed my fingers.