Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

[Bill C.]

Hey all....

I finally have gotten around to fixing the oil leaks from the intake manifold side rails.

I discovered after removing the intake that there was a substancial amount of oil comming up throughthe bolt threads that are open/thru-threaded. It also seems that some oil was being sucked into the intake ports in the heads, from the bottom side of the intake ports.

What can I do to prevent the issue with the bolts?

I have a NOS gasket set I was planning to use.
Would it be better from a sealing standpoint if I used a different gasket manufacturer for side gaskets?

I will use the GM rail gaskets since they have the tabs on them.

I need to strike a balance - reliability/sealing and judging.


Also ----
I noticed a build up of a hardened black substance on the valves, while looking into the intake ports. A couple of the valves were open enough I could somewhat see into the chamber, it looked to have carbon build up.

I use a can of SeaFoam with each fillup - I was told by a long time mechanic that it would help prevent the build up I noticed.
Is there a better additive I can use in the fuel to help cleanup things?


Any insight and suggestions are GREATLY appreciated!!

[Joe L.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

Hey all....

I finally have gotten around to fixing the oil leaks from the intake manifold side rails.

I discovered after removing the intake that there was a substancial amount of oil comming up throughthe bolt threads that are open/thru-threaded. It also seems that some oil was being sucked into the intake ports in the heads, from the bottom side of the intake ports.

What can I do to prevent the issue with the bolts?

I have a NOS gasket set I was planning to use.
Would it be better from a sealing standpoint if I used a different gasket manufacturer for side gaskets?

I will use the GM rail gaskets since they have the tabs on them.

I need to strike a balance - reliability/sealing and judging.


Also ----
I noticed a build up of a hardened black substance on the valves, while looking into the intake ports. A couple of the valves were open enough I could somewhat see into the chamber, it looked to have carbon build up.

I use a can of SeaFoam with each fillup - I was told by a long time mechanic that it would help prevent the build up I noticed.
Is there a better additive I can use in the fuel to help cleanup things?


Any insight and suggestions are GREATLY appreciated!!

Bill------


This is a common problem. Remove the through bolts. Carefully and THOROUGHLY clean the threads in the head. The threads MUST be 110% CLEAN. Clean the bolts (or use new bolts). The bolts MUST be 110% CLEAN. Apply sealer to the bolts. Non hardening Permatex or Locktite Pipe Thread Sealer with Teflon work well. Install the bolts and torque to spec.

The above will not necessarily improve the problem of oil being sucked into the bottom of the intake ports, if that's actually occurring. That's a whole 'nuther problem and, if it's actually occurring, can be a GIANT HASSLE to correct.

The stock type, embossed intake manifold gaskets are absolutely the best for sealing. You won't do any better with any other type gasket.

If the deposits on the valves are due to oil getting into the combustion chamber via the intake manifold gaskets, valve seals, or valve guides, then nothing you can add to the gas is going to prevent it. It might clean it some but the deposits are going to recur faster than any additive can clean it. So, you'll be "fighting a losing battle".

If the deposits are fuel-related, then I recommend adding Chevron/Texaco Techron additive. I think it's the best thing going. Also, consider using only Top Tier gasolines on a continuing basis. (www.toptiergas.com or, maybe, www.toptiergasoline.com)

[Bill C.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

Joe,

Thanks....

If I spray the side gaskets with copper permatex, wil that help with the oil entry?

I did notice that the intake bolts were not super tight when breaking them loose. I wonder if that was a cause?

[Terry M.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

I don't think the intake manifold bolts need to be "super tight." I haven't looked it up, and you should, but I think they are speced in the range of 30 to 35 ft/lbs. Torque has nothing to do with the oil creeping up the threads. Proper sealant is the answer to that.

If they are not tight enough oil can get into the intake passages though -- but that issue has more to do with proper machining and alignment than fastener torque.

[Joe L.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

Joe,

Thanks....

If I spray the side gaskets with copper permatex, wil that help with the oil entry?

I did notice that the intake bolts were not super tight when breaking them loose. I wonder if that was a cause?

Bill------


I don't think the "Copper Coat" will improve anything as far as side gasket sealing. I would be reluctant to use it. I once tried to solve this problem by using, among many other things, just about every type of sealant and gasket type that you could imagine (and some you could not even imagine). NOTHING worked.

So, you ask, how did I finally solve it? I did NOT; I gave up. And, it takes a LOT for me to give up.

As Terry mentioned, your oil seepage problem onto the surface of the manifold has nothing to do with bolt tightness. If you tighten the bolts to spec (30 lb/ft), you will find your oil seepage problem undiminished.

[Patrick H.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

Bill------


I don't think the "Copper Coat" will improve anything as far as side gasket sealing. I would be reluctant to use it. I once tried to solve this problem by using, among many other things, just about every type of sealant and gasket type that you could imagine (and some you could not even imagine). NOTHING worked.

So, you ask, how did I finally solve it? I did NOT; I gave up. And, it takes a LOT for me to give up.

As Terry mentioned, your oil seepage problem onto the surface of the manifold has nothing to do with bolt tightness. If you tighten the bolts to spec (30 lb/ft), you will find your oil seepage problem undiminished.

And, if you look at old Chevrolet small blocks that are actually driven, you'll see this occurring on a huge number of them. I might even say the vast majority but I don't want to overdo it.

Here's a video I took of this exact leak on the orange 72 I've been working on. No, I did not try and repair it yet.

http://www.youtube.com/watch?v=-MRaIcdm4Dw

[Bill C.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

Patrick,

Thank god mine was nothing like that - leak wise...
I would always find oil running down the back (it would sit on the block casting) and sort of pool up, but then would run down the side and settle by the oil pan rails...
It also did this up front too. The oil would run down the front over the stamp pad and then down to the oil pan.

It was not so bad that I loose a quart of oil in 300 miles, but the car would use a quart over the course of 700-900 miles.

To everyone - thanks for the great ideas.

Just as an FYI, I ordered a new set of intake bolts from Paragon and will thuroughly clean out the threads on the head before re-assembly.


What is so funny in all of this is I am doing this repair so I can sell the car... LOL I am doing a nice degreasing up front and will repaint all the pulleys, brackets, fan and orange parts too. Damn thing will look nice, might not want to sell it after this

[Michael F.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

I don't think the intake manifold bolts need to be "super tight." I haven't looked it up, and you should, but I think they are speced in the range of 30 to 35 ft/lbs. Torque has nothing to do with the oil creeping up the threads. Proper sealant is the answer to that.

If they are not tight enough oil can get into the intake passages though -- but that issue has more to do with proper machining and alignment than fastener torque.

If you were getting that much oil in the intake from warpage etc..? There would also be vacuum issues.

[Bill C.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

no vacuum leaks at all. Car pulled strong VAC at idle.

The oil burning was very minimal and the buildup on the valves were only on the ports near a tru-threaded bolt hole. I did not use sealer on the threads when I rebuilt the engine 3 years ago.

I will be sure that does nogt happen this go around.


Terry-----
Would it help if I take the intake to a machine shop and have them plain the sides and rails?

[Michael F.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

If theres no vac leak? There seerms to be no reason to machine the manifold surface. Sounds like using thread sealer will fix you up.
I don't see how you could be getting oil in your intake ports without there being a vac leak too.Maybe they weren't torqued enough and allowed oil and vac to seep?
If oil is going up the threads like so many do, the only way oil should seep past the gasket is a bad seal or lack of torque creating a bad seal.Torqued bolts will still seep without thread sealer.
Maybe you have a valve seal issue on those ports? I think temps are higher on those ports and are likely to have valve seal failure before the other. I could be wrong.

[Michael F.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

And, if you look at old Chevrolet small blocks that are actually driven, you'll see this occurring on a huge number of them. I might even say the vast majority but I don't want to overdo it.

Here's a video I took of this exact leak on the orange 72 I've been working on. No, I did not try and repair it yet.
http://www.youtube.com/watch?v=-MRaIcdm4Dw

That looks like multiple sealing issues. Like no thread sealer and a warped manifold. Either that or all the manifold bolts are loose.

[Terry M.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

no vacuum leaks at all. Car pulled strong VAC at idle.

The oil burning was very minimal and the buildup on the valves were only on the ports near a tru-threaded bolt hole. I did not use sealer on the threads when I rebuilt the engine 3 years ago.

I will be sure that does nogt happen this go around.


Terry-----
Would it help if I take the intake to a machine shop and have them plain the sides and rails?

Bill,

I would suggest you not worry about the intake seal, and deal with the oil coming up the threads. Follow Joe's instrustions to seal the fasteners and call it good. After all it is just a Chevrolet.

[Bill C.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

Terry,

I will just seal the threads....

Thanks..

[Patrick H.]

Re: Fixing Intake Manifold Bolts (leaking oil) - Need some Advise...

That looks like multiple sealing issues. Like no thread sealer and a warped manifold. Either that or all the manifold bolts are loose.

Manifold bolts are fine, but the intake gasket is almost gone in those locations. I'm leaving it alone until winter. I want the owner to be able to drive it a bit, and oil is cheap.