Head gasket replacement

[jw3500Ram]

My 12v has 350k and the front and rear corners of the head gasket are leaking coolant and running down the sides of the block. I need some advice on replacement.

I have been told to plan on buying a new cylinder head because most of them are cracked between the intake and exhaust valves. Is it advisable to put a new head on a bottom end with 350k?

 

[GAmes]

Whoever told you that is probably trying to sell you a new head. Depending on how the engine has been treated there is a possibility that the exhaust manifold has shrunk. If it is bad enough it will break the head. If it is less bad the bolts will bind and break when you go to remove them. A valve job would be a good idea with the head removed. If the exhaust manifold has shrunk an after market manifold is a good investment. I installed a three piece manifold on mine, but since then stainless steel manifolds have been introduced. If I had to do it again I would go stainless. Not knowing the history of your engine makes it impossible to say if the head gasket replacement is all you need. My original engine needed one at about 190k, and that was all it received. The engine was worn out and replaced at 800k miles. FWIW, I am convinced that genuine Cummins gaskets are made by Fel-Pro. They look identical side by side and the Fel-Pro will cost you a lot less. On the other hand, a Cummins upper gasket kit is a better buy to replace all the upper gaskets. I caution you against going the really cheap route of Interstate McBee.

 

[The patriot]

^ Good advice from an experienced guy.
In addition to that, make sure they hot tank it, magnaflux, and check it for straightness.
They SHOULD be doing this when doing a valve job, but I'd make it a point to mention it.
I'd also look for a shop that has some experience with these engines.

 

[jw3500Ram]

I told the mechanic I would supply all parts because I want to use genuine Cummins parts. I plan to order the Cummins top end gasket kit 4089650 since it has all of the required gaskets. I was definitely going to have the head milled and tanked. I was told he has done many 5.9 HG replacements.
So there is no problem putting a fresh head on a bottom end with 350k? I know you don’t do that with a gas engine.

 

[GAmes]

So there is no problem putting a fresh head on a bottom end with 350k? I know you don’t do that with a gas engine.

Once again, not knowing the history of your engine makes it impossible to say if the head gasket replacement is all you need. Only you can determine that. Does it have blowby? Is it using (burning) oil? Do you have an oil sample showing wear metals and contaminates? Does it have, and always had, a good air filter that is properly installed? Poor filtration is probably the biggest killer of diesels. Are you looking for an excuse to spend money on "upgrades"?

 

[jw3500Ram]

Thanks for the info. I will do more homework before moving forward.

 

[Woodenhead]

Solid advice here ^^
I'd have no issues freshening up the head for a motor with 350k if it hasn't lived a hard life and it's still running right. As a cheaper alternative, pull the head, have it magged (for cracks) and decked (for flatness) and if it checks out, slap it back on with a fresh gasket. Cracks between valves are not unusual and no reason to scrap a head. I had a crack on the exterior of a head back by #6 (maybe it was #5) injector, it was weeping coolant. That's a common failure and that head didn't go back on.

As mentioned above, use only an OEM Cummins head gasket. There's not really any reason to go to a thicker one unless they for some reason take a lot of material off the head to make it flat, at which point valves might get close to pistons but it's highly unlikely if it's the first time it's getting done.

The head bolts are "torque to yield" or something like that so they say to replace them. I've reused many, just torque them to a value I can't recall right now and leave them at that.

I'd be curious to know how many labor hrs your mechanic plans for the swap.

 

[jw3500Ram]

Thanks for the advice. I really don’t know how much money I want to put in that motor. The truck is starting to show its age. It still runs great just leaking coolant.
The mechanic didn’t quote hours he just gave a price of 600$ if I supply the parts and fluids.

 

[Bob4x4]

The head bolts are reusable.The hg kit comes with a gauge to test for bolt stretch.The biggest mistake I see on hg replacements have been improper torque and not having the mating surface clean enough and or an incorrect surface finish.

 

[jw3500Ram]

I have read that the head bolts were reusable. I will have them checked before reassembly. Thanks for the advice.

 

[Joseph Donnelly]

If you do a search, hopefully you will find my discussions on the topic from several years ago. As Bob4x4 said, get the surface very clean, use 100 q tips to mop out all bolt holes (or when you put in the bolts you will squirt all that stuff onto the deck). Torque in steps to 110-120 ft lb. The longer bolts may not want to go over 110-115. The heads usually crack from the injector hole to the intake valve seat, and between the intake and exhaust seats.