6.5 Head gaskets

[wigs]

just bought a 96 with an overheating issues. 200,000 miles Coolant boiling over, eating coolant. and so on. This is my first chevy diesel. I got the heads off the other night with no problem and found the heads cracked between valve seats on all cylinders. I found on the head gasket where it failed. I bought it knowing it had issues and for 3,000 miles never had an issue. Oncve it started to boil over i put maybe 10miles on it. I had an old vw diesel that had the same thing and everyone said that that was common and it's weird to see a head that isn't cracked. anybody else run in to this, or will i have to grab a set of heads.
second since i'm in there i'm doing new injectors, timing chain and gears,air and fuel filters, t-stat. It has new pump and pmd, and new glow plugs. i was planning on getting new exhaust to help it breath. Not sure if there is anything else i should do.

[Blazer6.5]

To help with the overheating you should think about getting a hi-flow water pump and maybe dual t-stats. Also check you fan clutch to see if it's working properly.

[MC]

Originally Posted by Blazer6.5

To help with the overheating you should think about getting a hi-flow water pump and maybe dual t-stats. Also check you fan clutch to see if it's working properly.

Go with a '97+ cooling upgrade.

[justy]

On a 1994 6.5 I drilled out the passages for more flow. Not sure if it's a good idea. But worked good. I wouldn't recommend it. But I agree, the 1997 heads or newer would help alot. High-flow/volume water pump for sure if you do alot of towing.

[chrisk1500]

Cracks between the valves are *normal*. This is not to say that the cracks are a good thing. Normally they won't cause any problems but they have been known to crack all the way into the water jacket in the head.

Your best bet is to get the heads sleeved. A shop will drive a brass sleeve into the water jacket so that if the cracks go any further, they won't leak.

The cracks you really need to worry about are the ones that start at a valve seat and run up towards the precup.

To fix the problem you can either install new gaskets and the old heads, have the heads tested and plugged and then install them, or buy new heads and install them.

[wigs]

All sounds good head will be getting checked later this week. Don't want to sound like a noob but what is the 97+ cooling upgrade consist of? It this something that I piece together or a kit that someone sells? Dual t-stats, who offers these? High flow w/p. Something easily availble?

[chrisk1500]

You can run with a HO waterpump and the single stat crossover. Just make sure you have an OEM t-stat in place (from the dealer)

[wigs]

Originally Posted by justy

the 1997 heads or newer would help alot. High-flow/volume water pump for sure if you do alot of towing.

In fearing for the worst I did some research for a set of new heads and also looking at the 97+ heads and found on Alldata that they list cyl heads for 96 with "high output," they also list the HO heads for '96, '97, '98, and '99. In 97 the also give you the option of heads without "high output". So are 96 and the 97+ heads the same?

[chrisk1500]

Never knew there were different flow rates in the GM cast heads....news to me....

The only heads that have been proven to have higher flow rates are the ones done up by Peninsular....

Unless we are simply talking about precup design here....or dare I say, confusing the t-stat crossover for heads?

[wigs]

Friend suggested gasket port matching, Never done this witha diesel. Done it with gas motors. Is this the same principal. Should there be anything to worry about?

[daustin]

I think the confusion is 'cause of the F and S engines, some of the parts houses refer to the F as an HO. Really the biggest difference is the EGR in the intake. If your heads are cracked, i'd look at CCH's (Clearwater Cylinder Head) aftermarket replacement heads. They are cast offshore but machined in their shop with all new hardware. I know several people running them, one has over 60K miles with no issues. Last time i checked, a set was only about $140 more than reworking the old heads.
Don

[chrisk1500]

Clearwater has a bad reputation with people as well....definately not all roses over there....

There are differences between S and F precups in the heads....easily changed....

[daustin]

I have heard good things about their new 6.5 head, but not so good stuff on other things they sell. Anything you wanna share more detail on?
Don

[chrisk1500]

Do some reading at the 'page'....you'll find what you want...

[D_Theater]

A similar discussion involving Clearwater's heads took place over at the 'Place. A member with a little bit of machine shop background felt Clearwater ripped him off, even though the heads are relatively cheap. The member thought the metallurgy was substandard and could never install those heads on any engine in good faith. His recommendation was to have your existing heads repaired, if possible.

I, on the other hand, used Clearwater's heads on a 6.5L Tahoe a little over a year ago. 47k miles later and that 6.5L is still holding together.

[D_Theater]

Originally Posted by wigs

Don't want to sound like a noob but what is the 97+ cooling upgrade consist of? It this something that I piece together or a kit that someone sells? Dual t-stats, who offers these? High flow w/p. Something easily availble?

You will see the best results by converting the engine to dual t-stats and the high-flow waterpump together.

You should also make sure your radiator is free of debris. I know leaves and bugs like to block air flow, and an indirect-injected diesel like the 6.5L needs plenty of cooling to stay happy and healthy.