Intake leaking coolant after head gasket change.

Hey guys been a while but i have yet another problem im wondering if i can get some help on.

In march of 2018 i decided to change the head gasket valve stem seals and all upper gaskets. The truck has not moved since first tearing into it and now its near a year later and no progress still after multiple times trying to fix it and im at wits end.

Ever since busting the original seals i have not been able to keep the intake from leaking. The head was torqued in sequence at different torques until reaching spec. The head gasket is on the correct orientation as well so i dont believe thats my problem. Now this is my 4th time reassembling the intake and the 3rd head gasket ive put on and it still leaks.

The head and intake were all taken to the machine shop so i know they are all flat. The head has been surfaced as well as the mounting surface for the intake. All 3 pieces of the intake manifold have been surfaced at their mating surfaces. Its leaking where the head and intake meet as well as where the lower and middle of the intake meet. Im using felpro gasket kit PN: MS 92964-3 and felpro head gasket PN:9388 PT.

What do you guys think my problem here is??? I will be taking it all the way back down to see the cylinder walls again since the last time it sat for months and now i can see rust and what looks like crystallized antifreeze in cylinder #4. It just doesnt make sense to me that it leaks in the same spot 4 times even with another intake and after having everything sent to the machine shop.

Any advice will be very much appreciated im almost ready to just tow it somewhere and let them deal with it but ive always worked on my own things and even though i run into problems i figure it out or you guys help me along the way just wanted to check in here before spending unnecessary money.

Thanks in advance
Thomas.

Truck is a 91 mighty max 4g64 sorry for leaving that out of previous post.

You have my complete sympathy.

What comes to my mind is that you are not aligning one of the dowels on the manifolds. That's just a gut feeling - likely, someone else will have a better idea.

Is the leak air or coolant, or both?

Hang tough, we'll get you through this one :)

Im not sure of any dowels on the intake???? Also unsure if its leaking air i get to putting coolant and it trickles out within 2 minutes its a decent leak. It pulls on tight when i torque it down so i dont think theres any misalignment there also the gasket surfaces are clean.

As a lifelong machinist/manufacturing engineer, mistakes are made. Have you verified that the mating surfaces are flat with a precision straight edge? You would be amazed how many 100% inspection parts I've seen come back through the doors with a missing hole, broken tool, or out of tolerance dimensions. I'm inclined to think something isn't flat if the leak keeps coming back at the same spot. Also, are you torquing your intake manifold starting with the center fasteners and working outward like you do on the head bolts?
Food for thought

Yes i am starting at the center and working my way outwards. Again its leaked with 2 different intakes now the one that came on the truck and the one i had surfaced that came off my junkyard motor. I have not checked with a straight edge but i find it hard to believe that both intakes would be warped enough to cause a leak especially if the one that came on the truck didnt over heat before going back on.

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Originally Posted by t97

Im not sure of any dowels on the intake????

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It's been a long time since I had to deal with my cylinder head, so forgive me if there aren't any dowels.

By the sound of it, it almost seems like there's a crack, somewhere. Also, check your coolant connections going into the manifold. (I'm sure you've done that, this is only meant to cover the check list).

Have you taken a mirror to look upwards to where the leak is? (Like a dentist mirror). This really is a baffling issue!! Keep us posted.

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Originally Posted by t97

Yes i am starting at the center and working my way outwards. Again its leaked with 2 different intakes now the one that came on the truck and the one i had surfaced that came off my junkyard motor. I have not checked with a straight edge but i find it hard to believe that both intakes would be warped enough to cause a leak especially if the one that came on the truck didnt over heat before going back on.

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I'm thinking more that the mating surface on the head could be off

Im going to try to get back over there today and try to get it torn down yet again and i will check the mating surface on the head. I can beleive thats what it is just sucks of it is because ive already paid for it to be fixed once.

Well guys went back to the house today and this is what i find cylinder 4 rusted to hell and water from last night pooled in cylinder 3. Any more suggestions while im waiting on parts yet again?

Heres a photo of the combustion chamber on cylinder number 4

One thing came to my mind, and it again refers to dowels (there ARE dowels for the head)...make absolutely sure the female side of the dowels is clean...I believe that would be on the cylinder head side, while the block has the dowels. Any dirt and gunk in the hole(s) could affect surface mating.

I know all ABOUT gunk in the hole affecting mating, but I'm speaking automotive, here, not ex-wives.

Ahhh okay i understand now you mean the dowels in the block on your first post you said dowels on the intake makes swnse to me now. I will definitely reclean both the head and block dowel holes.

No, actually in that other post I meant dowels for the intake manifold...which there aren't any. But there are definitely dowels for the block. Also, make sure the dowel head isn't mushroomed. In fact, once you've got everything cleaned up and ready to install, try putting the head on the block without the gasket, first, and see if there's any appreciable gap.


I wish you the best of luck...you've certainly been through enough!!

Will do i appreciate your help royster. Lets say that one of my dowels is in fact the culprit whats my next step???

You could flip the cylinder head upside down and fill the combustion chamber with a solvent. If theres a crack that coolant will leak through then the solvent should leak through and come out one of the coolant passages. I use wd40 from a gallon can.
And thinking about what royster said, if the head was resurfaced, the hole for the dowel is going to be shorter. Could be that the dowel is now longer than the two holes it fits in and needs a little bit of grinding. The gap test with no gasket is a great idea.

I, for one, really wouldn't know what to do if I had to replace the dowel(s), but Mr. Giovanni is on the right track with grinding it down a bit. For the leak you report, I can only imagine that there is a resistance when you torque the head bolts, and those dowels are the only thing that would be the culprit.

I wouldn't be afraid to grind down the dowels too much: they are only there to align the gasket and head. So check on those things real carefully, and perhaps do that leak test as Giovanni suggested. We'll get 'em this time, t97!!!

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Originally Posted by royster

I, for one, really wouldn't know what to do if I had to replace the dowel(s), but Mr. Giovanni is on the right track with grinding it down a bit. For the leak you report, I can only imagine that there is a resistance when you torque the head bolts, and those dowels are the only thing that would be the culprit.

I wouldn't be afraid to grind down the dowels too much: they are only there to align the gasket and head. So check on those things real carefully, and perhaps do that leak test as Giovanni suggested. We'll get 'em this time, t97!!!

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They just pull out of the block. Soak around them in a bit of carb cleaner and then usually you have to grab them with a pair pliers and give a little twist. If you kick up a burr with the pliers you can just stone or sand it off. I usually remove them when I clean the deck on the block.
If you really bitch them up, Randy who runs Engine Machine Service out of Ohio (who I bought my head valves and springs from) has a 2 pack of the new dowels on his conquest/starion parts page under "other engine parts" $4.10 for a 2 pack.

Okay guys i will be looking into the dowels next time but it still doesnt explain why my intake would be leaking at the head.

there coolant passage at the back of the intake that if the head doesn't seat right, it could twist and cause the leak.

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Originally Posted by t97

it still doesnt explain why my intake would be leaking at the head.

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Is the leak coming down the side of the block? By the photos, it obvious it's leaking into the cylinders, but if it's also leaking down the side of the engine, then there is something else to be pondered.

I ask the board (because I do not know) - if the head was shaved, would the head bolts be a fraction too long? I'd suspect that the thread holes run slightly deeper than the bolt length. What I'm getting at is: would a washer on the head bolts be of benefit? Or something you shouldn't do?


Hey, Mr. Geezer! What's your take on this?

Ok Roy, just for you lol. You'd have to shave off a LOT of metal to cause even the remotest chance of the head bolts being too long. The head bolts already have washers on them and I can't see there being a benefit of adding washers (it starts to look like a ghetto fix so, not good...) Going by those photos either it wasn't torqued down properly off the bat, it wasn't retorqued after the bedding in period, the top of the block is warped or the head recon was garbage. You can't lop a lot of metal off these heads due to the quench area on either side of the combustion chambers. The 4G64 heads have to be handled with kid gloves too. They are known to warp so badly that they bind the cams and cause them to snap (we've seen it on MR50 2 or 3 times). I'm gonna rant now about what guys think is ok and the realities behind it.

I don't approve of a shop milling heads to return them to a true deck without baking them first and pressing them straight. The reason behind it is it's not just the face of the head that is warped - it's the entire head. That means the deck face, cam bed - everything. It messes with combustion chamber volumes as well. And then there are situations where one particular head is sensitive to heat like the SOHC 4G64. I don't know what is the design feature of this head that risks the head warping enough to bind a cam but running it after being warped leaves it at risk of severe cam bearing surface damage. This can happen with any OHC head design - the head is alloy, the cam ain't and it's never gonna bend for anything. Listen out for machine shops that know their magic and pay the extra coin if you have to. I pay an average of $300 AUD for one shop to do my headwork and they have always been spot on. The only facet of head reconditioning I do is my own porting due to how much it costs to have a pro do it and what one guy 'thinks' vs what I want. You don't want to pay someone 10-30 hours on a head only to get it back looking - meh.

It seems to be leaking at the mating surface where the intske meets the head. Unsure how it couldve been torqued wrong it was torqued in sequence at 3 different torques working up to spec. It was done with my electronic torque wrench then checked a 3rd time with my clicker type. I feel as if its leaking from the coolant passages into the intake ports then in through the valves. The motor has not ran so it hasnt needed to be retorqued yet.

Also my truck has never overheated while ive owned it and i havent had problems with the headgasket so shouldnt that ruke out a warped block??

I doubt it is the block. But You should check the block, head, manifold mating surface on head, and the manifold its self for straightness. If they flubbed on the head, when you torque it down it will twist and the manifold mating surface won't be straight anymore.
Buy nice and you only cry once ;) https://www.amazon.com/Starrett-380-...+straight+edge

Before you pulled the head off was there water pooled on the top of the intake valves?

It wasnt pooled but the top of the valves were rusted.

Well guys got the head back from the machine shop they surfaced the the bottom as well as the intake gasket mating surface and replaced the studs again. Put everything back together with a fresh set of felpro gaskets and all is well. I did nothing different this time than any other time so im assuming they messed up last time the head was at the machine shop. Thanks for all the input guys.

Fingers crossed for you that this is done and dusted.