Head Gasket Replacement - Need Direction

I have removed the heads on my 1998 GMC Sierra K2500 6.5L turbo (135k miles) after having problems with loosing coolant and fluctuation of the coolant temperature typical to a head gasket failure. I also had bubbling in the reservoir even after extensive tries at getting all of the air out of the system. I had no signs of coolant in the oil and the truck was still running great.

I'm looking for some direction as i have the heads off and the head gaskets don't appear to have a major failure between any of the coolant passages and the cylinders themselves. I was expecting (almost hoping actually) to find a blatant failure. The bottom of the cylinder heads and the mating surface on the block are in very good condition.

This is the first time i've removed heads and figured it would be worth the money to take them to a shop and have them cleaned and inspected for cracks. I haven't cleaned them up yet to inspect closely myself. Are there any particular areas in the heads that are prone to crack that i should inspect? I live near Iowa City, IA and would be open to suggestions for a reputable shop.

I've done tons of research and searches on this site to get where i am now and am planning to install new injectors and glow plugs upon installation of the heads. Any additional help would be greatly appreciated!

interestingly enough, im digging into my 95. had the exact same symptoms you did. check around the valves and precups. chances are you will find some cracks. whether you decide to reuse the heads is your call.

I am in the process of putting mine back together. For the third time. This time I took the heads in to have them sufaced and pressure tested. This is due to leaking on a new set of heads. I am in the position now that if I ever remove heads for a block again, I'll be taking them in for trueness and a pressure test.

It would be a good idea to have your heads tested and checked for warpping.

John

So I've contacted multiple shops regarding having my heads hot dipped, magna fluxed, and inspected for cracks. The comments that I keep getting back are that they're "all cracked, happens with all 6.5's". I understand that there might be microscopic cracks but not all will lead to coolant leaks into the combustion chamber.

Is pressure testing the head the only way to confirm the condition of the head??? Is this something that most machine shops should be able to do?

They should. And they should do it without the snappy comments.:p Look at them good when they are off. Between the valves and the pre cups. Mine were cracked between the valves and the pre cups were cracked beyond the fire ring. Even the new heads had cracks in the pre cups after 100 miles. Just not that bad that they went to the fire rings. I wiped the heads down with acetone and the cracks were very visable.

As it was discribed to me. Magnafluxing with show the cracks. Pressure testing will tell you they are leaking. As for the processes I'm not sure but that is how it was explained to me by several mechanics.

John

When they magnaflux a head they magnetise the head then put some iron powder and the cracks will become visible because of the high concentration of magnetic flux at the cracks. It is a really cool process, and it will be very obvious where the heads are cracked, and how big of a crack, once it is complete.

So I got a call back from the machine shop (Arnold Motor Supply in Washington, IA) today regarding my heads... Not great news. The guy said there are cracks all over and said they frankly look like a piece of cracked glass. He said he DID find particular cracks that had rust along them that appeared to have let water through.

He said he could source either rebuilt heads or new heads from Midwest Cylinder Head & Machine in Nevada, IA. Midwest Cylinder Head uses 'oven fusion cast iron welding' to repair head cores. He quoted me $520 each for NEW or $440 each for Rebuilt. For the $80 price difference I would think new would be the way to go but i could be wrong.

So a few questions...
1. Should I go NEW or Rebuilt?

2. If I go with NEW is there anything in particular I should ask? Where do they buy from, etc?

3. Since I now know the heads were leaking compression into the coolant and some coolant into the pistons is there anything else in particular i should inspect for on the pistons? So far the tops of all of the pistons look smooth and undamaged. The truck was running great prior to disassembly.

Any help would be much appreciated.

Thanks!

New GEP heads (the latest-greatest) for around $600 each, or new Clearwater (arrived by boat) for a lot less. Unless you KNOW the origin of the new heads you were offered, they are probably way overpriced (and perhaps no better than what you have now).

Robyn could tell you a few things about these cylinder heads. She's been a little up-close-and-personal with them lately.

I have been down the head road before. :eek:

My suggestion is to stay as far on the other side of the street as you can be from any welded 6.5 heads.

I personally will not use any high mile 6.2/6.5 head.

They are used up by around 200K miles. Any cracks other than the little ones between the valves are a death sentence, especially cracks on the fire deck.

As Maverick mentioned

Clearwater cyl head (The last set I got a quote on were $670 per set to my door)

The GEP (AM General brand new US made) were recently quoted at $1000 a set to the door.

Both of these are complete and ready to bolt on.

I have personally used the Clearwater heads and know several others who have used them and had great luck.

They come with a good warranty.

The castings are new (China) and are, I am told, machined in clearwaters own shop and a good many of the parts (Valves etc) are reconditioned pieces.

Clearwater sends a shipping tag that will return your old heads to them.

They strip out the parts and sell the cast iron scrap.

If your on a budgit, get a set of the CCH heads, they are not a bad choice

Here is a link to CCH http://cylinder-heads.com/

Look the block decks over reeeeeeeeeeeeeally well for any signs of errosion around the area where the head gaskets fire ring sits. This is especially important on cyl's 1 and 2
(two front ones)
If you find any areas that the fire ring has worried a groove into the block, then there can be trouble.

The area near the water port on the front two cylinders is notorious for erroding the deck some.

If the decks are good, clean them well and make sure all the surfaces are oil free when installing the new gaskets. USE ONLY FELPRO head gaskets on these engines.

The late style gaskets from Felpro have a reinforced area at the water ports on the ends that the factory ones did not.

Always use new bolts as these are a one time use bolt. They come with sealer on them and are ready to use. (Follow included torque instructions)

Do not use any sealers on the head gaskets, DRY only

Good luck

Missy

Decided to go with the new heads. They're at the shop and ready to go. Still need to pick them up.

I was working on cleaning up the block deck. I can't see any areas where it has erroded around the cylinders or around the coolant passages.

Thanks for the tips regarding installation of the heads. I have new injectors and glow plugs that will go in as well.

I had purchased the Felpro gasket kit for the upper portion of the engine (I also purchased the Felpro head gaskets). This kit included exhaust manifold gaskets, valve cover gaskets, thermostat housing gaskets, etc. When i removed the exhaust manifolds from the block, there were no gaskets in there. Is there suppose to be? Should I install them when i reassemble?

Also, I had read some previous postings about NOT using the valve cover gaskets, but using gasket sealant instead. Which should i use?

Finally, are there any tips regarding refilling the coolant, purging the fuel injection, or other general 'start-up' items to make sure i don't damage anything on the first crank?

Thanks for the help.

Unless you plan to go back under the valve covers soon, use sealant and toss the gaskets. Gaskets are fine, but only short term. They will leak. Count on it.

No OEM exhaust gaskets. With new heads, you shouldn't need to use them. Check the manifolds for a true, clear surface. If they are good, no gaskets. If not, have them milled true. If you don't want to do that, use the gaskets or risk it without (my preferred method). The gaskets may leak after some use. Without gaskets, small leaks will seal themselves over time (not a long time), and any leaks will be very minimal. Leaking gaskets are large leaks, especially under load when boost levels rise, and have a tendency to "blow" out. This causes a serious condition which can cause serious collateral damage (and leave you stuck, roadside). Exhaust gaskets, IMO, are a shortcut, and may be a shortcut to a serious crippling failure. No problem using them on a N/A engine, though (little to no exhaust back pressure).

Refill the coolant with the bleed valve on the T stat housing OPEN.
When the coolant runs out, close the valve and fill the reservoir to the cold line.

Recheck the levels after the startup/warmup and add accordingly.

I agree with Maverick on the VC gaskest. USE THE HIGH TEMP SILICONE
The exhaust gaskets dont fit right and will not work, clean the manifold surfaces and bolt them on metal to metal.

The startup after the thing is back together is easy.

Make sure you have airfree fuel to the IP (Purge the hose by activating the lift pump.

Leave the glow plugs out, spin the engine until fuel mist blows out the plug holes.

Install the plugs and the engine will start right up.

This method saves the starter and really speeds up the process.

The IP does not have to fight compression to purge the air from the lines and the injectors.

15 to 30 seconds on the starter will do it (Usually) and the engine will be ready to go.

Also the engine spins nearly twices as fast with the plugs out.

This should get you up and going.

Missy

Refill the cooling system with distilled water only!!! keep the unfriendly minerals out!

Working on reassembly...
So far I've got the drivers side head, head gasket, rockers, pushrods, and new injectors installed. Surfaces were cleaned prior to assembly and new head bolts were carefully torqued. Few more questions i was hoping for help with:

1. I've got new gaskets for the coolant block off plates for the back of the heads. Should i use RTV with the gaskets or just the gaskets?

2. I cleaned up the valve covers to remove the dirt/grease. I'm having a hard time getting the old sealant off the valve covers. Any suggestions for removing it? Wire wheel maybe?

3. The heads have a tapped hole for the coolant sensor. On my pickup, the sensor is on the driver's side and the passenger side is not used. I forgot to get the plug out of the old head for the passenger side. What is the thread size for the plug? Is it NPT or some sort of metric tapered thread?

4. A couple of the exhaust manifold bolt heads got slightly rounded during removal. If i want to replace them, what should type of bolt should i use? Grade 5, plain carbon steel or zinc plated?

Hope to get much more work done this weekend. I appreciate all the help and tips!