Someone shoot me! Intake Manifold STILL leaking coolant.

[brown7373]

The stock cast iron 4 bbl intake is STILL leaking on my new crate 350/290 (previous thread March 7 http://67-72chevytrucks.com/vboard/s...t=Coolant+Leak). I removed the manifold, re-cleaned everything, chased the bolt holes & cleaned and used new gaskets. I used Ultra black around each port and bolt holes on both the head surface and the manifold surface. I used ARP Thread Sealant on all the threads. After I filled with coolant, I get a leak from #2 right bolt. Not as much as before, but it still seeps out. I checked the 30 torque setting with 2 different torque wrenches.

Where do I go from here? If the manifold has been cut previously, could that be my problem? And how does a machine shop know how to cut it now to match the new engine? Getting the truck to a machine shop would require towing it there, but if required, then so be it.

Any new ideas or comments?

I have read that the factory would routinely use radiator Stop Leak in case of any leaks. Anyone think this might help, or is this just a witch doctor fix?

[BugzC10]

Originally Posted by brown7373

The stock cast iron 4 bbl intake is STILL leaking on my new crate 350/290 (previous thread March 7 http://67-72chevytrucks.com/vboard/s...t=Coolant+Leak). I removed the manifold, re-cleaned everything, chased the bolt holes & cleaned and used new gaskets. I used Ultra black around each port and bolt holes on both the head surface and the manifold surface. I used ARP Thread Sealant on all the threads. After I filled with coolant, I get a leak from #2 right bolt. Not as much as before, but it still seeps out. I checked the 30 torque setting with 2 different torque wrenches.

Where do I go from here? If the manifold has been cut previously, could that be my problem? And how does a machine shop know how to cut it now to match the new engine? Getting the truck to a machine shop would require towing it there, but if required, then so be it.



Any new ideas or comments?

I have read that the factory would routinely use radiator Stop Leak in case of any leaks. Anyone think this might help, or is this just a witch doctor fix?

Could it be the manifold has a crack in it? Have it manufluxed / checked for cracks.

[geezer#99]

Did you use a step bolt or are you still playing with that bracket?

[Wrenchbender Ret]

Drain the coolant down below the manifold level. Remove the bolt & put some Ultra black on it. Put the bolt back in & leave over night. That should solve it.
The factories & dealers used Bars Leaks for preventive & recalls & warranties. I have used it for many years with great success. If put in correctly it will NOT plug up radiators or heater coils.
George

[brown7373]

Originally Posted by geezer#99

Did you use a step bolt or are you still playing with that bracket?

I am using the factory bolt and the factory bracket. Eliminating the bracket would also eliminate my A/C. I live in south Florida. That is not going to happen.

I will try draining down and resealing the bolt.

I don't think the manifold is cracked. I see no evidence of that and the leak is coming through the bolt hole...or so it seems.

[geezer#99]

IIRC from your previous pics that bracket is adjustable and can be raised up enough to use a step stud. Only about 1/4 to 3/8 inch.
Use a step stud for both ends of the bracket to keep it square.
Don’t use lock washers on your bolts or studs where they contact the intake.

[RustyPile]

Originally Posted by brown7373

The stock cast iron 4 bbl intake is STILL leaking on my new crate 350/290 ...............<snip>.............. I have read that the factory would routinely use radiator Stop Leak in case of any leaks. Anyone think this might help, or is this just a witch doctor fix?

Stop Leak type products is just a band-aid fix.. I worked at GM dealerships during the production era of our beloved trucks.. Several times a year we received service bulletins and various other "service reminders", discouraging the use of coolant additives meant to seal up leaks.. "Repair or replace" was the order of the day.......

Make sure the bolt isn't too long and bottoming out at the end of the threads before cinching down against the manifold.. I've had good luck with pipe dope on the stubborn "leakers"..

[brown7373]

That A/C bracket is between 3/8 and 1/2 inch thick (hard to measure on the engine and the 2 step studs I have only about 1/2 on the stud, so that won't work.

The heater hose fitting is also right beside the 2nd bolt, so I am also going to reseal it and cut off a little of the hose to give it a new surface.

This is my first Chevy engine, although just an install of the intake on a crate engine. I have rebuilt a Pontiac 455 3 times and a Ford 390 several times and never had any issues like this stupid one. Is the Chevy just extra touchy?

[geezer#99]

Make a step stud.
Use readyrod cut to the right length so your bracket will bolt back on.

The stud by your choke stove is likely readyrod.

[HO455]

Try installing it with a step stud and leave the AC bracket off for now to see if it seals. If it still leaks at this point I think it is time to pull the manifold off and do a dye penetrate test around the hole in the block to see if you have a cracked block. The open on the bottom threaded holes are more susceptible to cracking if torqued if the when intake wasn't sitting perfectly flat. Or if the bolt ran out of threads and was over torqued. Either way you may be the victim of Virgil Armstrong previous owner.
If there is a crack it the machine shop should have caught before machining the block.
I have had this exact slow leak on the driver side slowly repair itself as debris in the coolant filled the spot that wasn't sealing.

[brown7373]

I have 2 stud among the 12 intake bolts. One holds the support for the oil fill tube and the other attaches the transmission controlled spark solenoid. The solenoid stud is smaller diameter than the oil fill support, and nether are long enough to attach the A/C bracket.

What is readyrod? Is that just a length of threaded rod cut to length and then a nut screwed on to torque the manifold, and the threaded rod above the nut to attach the bracket?

[HO455]

Ready rod is also known as All Thread is like you said threaded rod. Cut it length and use one nut to secure the manifold and a second one to hold the AC bracket. I'm not sure it will make a difference on a low torque item like an intake manifold.
If you have to remove the intake I would also check it for flatness and that both sides are true to each other just to rule them out of the list of suspects.

[54blackhornet]

Did you consider getting another manifold ?

[brown7373]

If I can't eliminate the leak, then the next step will be to consider a new manifold.

I sealed the questionable bolt again and also the heater hose bib. I am really going to feel stupid if it turns out to be the heater hose leaking. I did discover it had coolant around it, and it would run down to the #2 bolt. Should know later today.

[rpmerf]

If you are checking the manifold for flatness, might check the head too. Unlikely, but worth a check.

I've heard about intake issues when a head is milled. Since the heads are in a V shape, the manifold may not fit if the heads were milled enough. I've heard of people milling the manifold to fit. There are double thickness gaskets. Most stock gaskets are 0.060" or 0.063". There are a bunch in 0.120" or 0.125" thickness.

I know you say you do not want to eliminate your bracket can therefore AC, but can you do it temporarily?

Can you cap off the heater hose plug? Put a plug in there and put a bunch of teflon tape on there.

[toolboxchev]

My SWAG for checks and knowledge.

If your heads were milled too much it would make the manifold difficult to get a seal.

Think like widening the V in which the manifold sits the gap has grown and now the gaskets, permatex cannot do its job. Intake manifold actually have a slight curve or bowl to them. You can get away with much more torque on the stock iron ones.

One thing to look at is how much space do have where the intake manifold meets the china wall on the front and back of the engine. When the heads are milled those old stock rubber gaskets will squeeze out, that is why most use a bead of Permatex the

[KJSR]

I thought the intake bolts were in blind holes? It have been a while since I worked on early heads.....sealing the bolt would do nothing.

If you have coolant higher than the bolt I would suspect that. Interested in what you find.....

[garyd1961]

The type bolt and the brace isn't going to matter as long as the manifold is torqued down. Cast iron isn't going to flex and make a weak spot.

[Steeveedee]

Originally Posted by KJSR

I thought the intake bolts were in blind holes? It have been a while since I worked on early heads.....sealing the bolt would do nothing.

If you have coolant higher than the bolt I would suspect that. Interested in what you find.....

They have been blind on every SBC I worked on before the 1985 production year. After that maybe something changed. The lower row of head bolts gets sealer on the threads, though.

[RustyPile]

I've been following this thread and the other one too.. There is a lot of miss-information being posted here, but I won't point any fingers at the guilty.... The two end bolt holes are blind holes, and don't "open" into the water jacket.. All remaining bolt holes open into the lifter/pushrod area and are exposed only to oil.. The only coolant that might appear around the end bolts has to either come from a leaking gasket or from an external source.. If any coolant appears around any of the other bolts, IT HAS TO PUDDLE THERE AND COME FROM AN EXTERNAL SOURCE..

Get yourself a cooling system pressure tester.. Clean up the coolant residue, top off the coolant and use the tool to find the leak without running the engine or relying on guess work..

[Steeveedee]

Originally Posted by RustyPile

I've been following this thread and the other one too.. There is a lot of miss-information being posted here, but I won't point any fingers at the guilty.... The two end bolt holes are blind holes, and don't "open" into the water jacket.. All remaining bolt holes open into the lifter/pushrod area and are exposed only to oil.. The only coolant that might appear around the end bolts has to either come from a leaking gasket or from an external source.. If any coolant appears around any of the other bolts, IT HAS TO PUDDLE THERE AND COME FROM AN EXTERNAL SOURCE..

Get yourself a cooling system pressure tester.. Clean up the coolant residue, top off the coolant and use the tool to find the leak without running the engine or relying on guess work..

I didn't want to confuse the issue more than it already is, so I only referred to the bolts at the water jacket. Though by leaving that bit about bolts penetrating the lifter galley, I may have made it worse.

[Killer Bee]

Originally Posted by RustyPile

I've been following this thread and the other one too.. There is a lot of miss-information being posted here, but I won't point any fingers at the guilty.... The two end bolt holes are blind holes, and don't "open" into the water jacket.. All remaining bolt holes open into the lifter/pushrod area and are exposed only to oil.. The only coolant that might appear around the end bolts has to either come from a leaking gasket or from an external source.. If any coolant appears around any of the other bolts, IT HAS TO PUDDLE THERE AND COME FROM AN EXTERNAL SOURCE..

Get yourself a cooling system pressure tester.. Clean up the coolant residue, top off the coolant and use the tool to find the leak without running the engine or relying on guess work..

in bold - nailed it! invaluable tool for this diag.. pressurize cold for 'cold water leaks' or operating temp, engine off to eliminate engine vibration migrating leaks other places.. pressurize to cap rating should pronounce leaks.. keep an air nozzle handy for clearing suspect areas to locate precise leak points..

Stant makes a great shop grade kit for $50-$70.. well worth it on your first accurate leak diag

good luck!

[cardude]

Some good reading on the subject -

http://garage.grumpysperformance.com...stributor.464/

[brown7373]

So now is the point that I have to admit I am an idiot! Seems the leak was from the heater hose, not the intake. All the resealing didn't do anything but cost me a lot of time, some money and lost sleep. The coolant seeped out from the heater hose and right down to bolt number R2, and I completely missed it.

So anyway, thanks for all the help. I am now fixed and ready to proceed.

[BugzC10]

Originally Posted by brown7373

So now is the point that I have to admit I am an idiot! Seems the leak was from the heater hose, not the intake. All the resealing didn't do anything but cost me a lot of time, some money and lost sleep. The coolant seeped out from the heater hose and right down to bolt number R2, and I completely missed it.

So anyway, thanks for all the help. I am now fixed and ready to proceed.

Hey..join the club, we've all been there done that.