two questions

[jasondmann]

My greater concern is my cooling system.

I just finished a 3000km pull across Canada (Winnipeg to Ottawa) . 1000km into the the trip I broke the belt tensioner pulley. I got very hot but shut it off pretty quickly, lost about 4-5Litres of coolant. Got the part replaced, top up coolant, bled the air out and continued trip. Truck ran well no problems.

Now the truck looses a lot of coolant while idling. I ran the truck up to temp with the rad cap off and also let it gravity bleed. Weird thing is when it was idling I would get bubbles (cap off) but not when the engine is turning faster. I did notice that the heat is warmer when the engine speed is up too. It did finally stop bubbling so I will check it again this afternoon.


Second question, I guess when the pulley broke the belt must have hit the vacuum line to the turbo waste gate. I didn't notice until the end of my trip. Does the line control when the gate will open? Because I did not notice a difference in power or fuel economy, I was only pulling ~3000lbs and the truck was loaded too.

Thanks for all your help.

[Robyn]

If you are seeing bubbles in the coolant tank things are grim in Gotham city Batman.

Probably a head gasket left its post.

You need to remove the water Xover and with the belt off, see which side is bubbling.

Very likely a head gasket on an end cylinder. These engines don't like getting hot.

A short hop to 240F is usually survivable but anything over that can agravate a head gasket thats on the verge.

Keep us posted

Robyn

[jasondmann]

I was really hoping for a diffrent response. I was sort of thinking the same thing...

The needle went way past the "red zone". I was passing a police car that had somebody pulled over while going up a hill (throttle pedal on the floor) at the same time. It took me at least 5 seconds to get the truck shut off and pulled over (saftey first, me and others).

I ran the truck again this afternoon, more bubbles... Kind of weird that I made the rest of the trip though. I've driven approx 2000Km since I overheated.

Can the gasket be changed with the engine still in the truck? I am just starting to think of all the things that have to come off... I just moved and am renovating, I'm too busy for this now.

Should I be worried about anything else, like a melted piston or head dammage? I have 351,xxxKm on the engine untouched as far as I know. It has always been reliable but a little weak and tired.

I still find it weird that I was able to go the 2000km for the rest of the trip trouble free.

Thanks for your help

[jasondmann]

Well I got the engine torn down and the RH head off. I found the #8 cylinder had a blown head gasket (I made the tear bigger in the picture). But to my disappointment I found two cracks in the head. One between the valves on the the #8 and one between the valves on the # 2, I am surprised that I did not see white smoke. I haven't taken the LH head off yet but it doesn't matter I'll need to replace both heads. I'm going to look through supplier list on the diesel page to see who is best. Any recommendations?

I sure miss working in a shop, at least it has been sunny the last couple of days. I'll attach a few pictures, the second last one is something that has been extremely helpful on this job and the last is my helper.

Happy Easter
Jason

[JohnC]

Common problem. There is a low cost fix here (http://www.thedieselpage.com/members/gmheads.htm).

Unanswered question in your first post: vacuum keeps the wastegate closed; no vacuum, no boost.

[Yukon6.2]

Hi
Most of the time the cracks between the valves don't leak.There is a procedure to fix the cracks that is fairly cheep.With the miles that are on the engin you might want to save up for a rebuild and patch it up for now.I'v read lots of threads were the heads were used with cracks and never leaked.
Do some searching and reading befor you buck out for new heads,There are lots of options,and reserch the heads if you decide to buy new,there are a lot of made in china parts,some seem to be ok,but i belive you shouldn't have to pay big bucks for the china stuff.
Good Luck
Thomas

[jasondmann]

Thanks so much for the help and advice. You got me to join as a member and I must say that there is so much more information available there. I would recommend for anyone who isn't a member to join.

I read the procedure on how to repair the cracks between the valves, seems easy enough. My grandpa used to be a machinist so next time I'm back home for a week or so I was going to pull the heads and do the repair with him, until then I was just going to change the head gasket.

Well I got the RH head cleaned up today (LH has not been removed yet) and noticed that not just 2 and 8 but all cylinders have a crack between the valves. Then I saw that all of the pre-cup chambers are cracked as well, the insert not the actual head. Is this something that should be repaired, can it be repaired or should I be back to plan A with new heads? I can post pictures if needed.

I need this truck to last another 4-5 years while I'm at school. Then I will be looking at a new one. But I want reliability from this truck, I am not going to be towing large loads or very often, nor will I put many miles on it. I would like to get it running so that I can go for an inspection and emissions test because I just moved.

Thanks for all of your help much appreciated.

Jason

[jasondmann]

I got the LH head pulled off yesterday. I found similar cracking on the pre-cups and between the valves. On the No. 1 cylinder the crack between the valve is actually two cracks and once I cleaned it up a chunk fell out.

I called a machine shop in town and they didn't recommend fixing the heads. They said I was looking at about $600 CND to sleeve the coolant passages and replace the pre-cups, and then I told him about the chunk that came off he said no way. So I ordered a new set of heads, new stock injectors, new glow plugs, new head bolts and an install kit from SS Diesel Supply. I know that I could have got cheaper parts and not gotten the injectors and glow plugs but I figured that I may as well do it right. Hopefully the parts arrive next week and then I can have it back together before I go out of town.

I'll post again when I'm done or when I need help remembering how to re-assemble. I took pretty good notes so hopefully smooth sailing.

[Robyn]

With the $$$ figures to fix the used heads, I would call Clear water Cyl head and order a set of their new heads and be done with it.

I have used these and the cost was $670 for two new heads delivered to my door

I have not used stuff from SS diesel but your definately smart to do it the way you are.

Replace the rocker buttons too and be sure to get the pushrods back in with the copper colored balls up.

Best

Robyn

[jasondmann]

The UPS truck came today! I am about to start assembly but have a question.

When I disassembled I did not notice gaskets on the exhaust manifold or the turbo. Is this normal or should I go to NAPA tomorrow morning?

Thanks for the help.

[DennisG01]

None on the exhaust manifolds - as long as they're true and you don't see any signs of leaking. I used one at the turbo, but not sure if you have to. Or did I? I can't remember, now.

[ronniejoe]

Usually don't need gaskets between the manifolds and heads. The turbo usually has a metal compression gasket under it, but can be run without as long you don't hear any leaks. About any turbo shop should be able to supply you with the gasket for the turbo mount.

[jasondmann]

Thanks for the response about the exhaust.



I got it all put back together today, well mostly except for trim pieces.

Bled a few injectors and it fired right up, cleared up and sounds great. BUT I have a lot bubbles in the coolant again. I thought that it may have just needed bleeding but that is not the case. I let it sit over diner to gravity bleed with the vent open on the crossover. Went out after dinner and it was almost like it was hydro locked, tried twice and it wouldn't turn then third time it went. Still have a lot of bubbles, the air is coming from the hose that comes from the top of the rad to the surge tank (obvious).

I installed brand new heads and gaskets and bolts. The only thing that I can think of is that I did not install the two little copper inserts between block and head on bolts # 8 & 9 on the right hand head. They were stuck in the old head (LH stayed in block) I looked and they looked like they were just to hold the gasket during install. It is possible that I damaged the RH gasket because it did slide around a bit.

When originally diagnosing this problem a few of you recommend taking off the crossover and watching which side for bubbles. It looks like the intake has to come off so that I can access the crossover bolts. Can I run the engine (only momentarily) with the intake off? It isn't a gas engine and doesn't need the intake to mix fuel... I'm going out of town for a while but will likely try this when I get home.

I am frustrated about having to start over, buy new head bolts and gasket again but don't want to do both sides if I don't have too.


1. Can I run it without the intake on?

2. Do the copper inserts between the block and head on bolts 8 and 9 need to be installed?

Thanks for all of you help

Jason

[93GMCSierra]

It can run without the intake, just be very careful of objects that might go down inside while its running.

[jasondmann]

Does anybody know about these copper inserts? There are two on each side, I'm going to take it apart again in a week. I'll be extremely careful when running without the intake. Thanks again.

Jason

[simon]

These are dowels to align the heads and the gaskets to the block. You pretty well need them.
How did the intake fit,cause if the heads are not paralel to the block and each other you'll have fitting prob with bolts and everything.

it may well be out of order and cause your air bubbles in the coolant.

You dont want to hear this,but I say,rip her open again

[jasondmann]

The intake was fine, everywhere was touching before I torqued it down.

I will take the cross over off and see which side is bubbling from, hopefully only one side.

I suspect that I tore the head gasket on the side that is missing the dowels. Can I get the dowels from NAPA or are they a dealer only part? The old ones stayed in the old head and got bent when I put the head down on some plywood.

Thanks everyone for the help. I should be tearing into it again on Monday.

Jason

[jerry598]

I'm currently in the middle of this same job and will be ordering new heads Monday. The 6.5 Repair and Troubleshooting guide available on the Diesel page is worth the price, and would have answered alot of your questions. Those alignment dowel pins are available from GM for $2 each. Did you clean the head bolt holes real good? It's required to get the proper torque. And the gaskets should be Felpro, which come with a coating of sealant. Did you clean the mating surfaces really well? I did mine with a straight-edge razor and 80 grit, wet, dry paper. You might check the block deck for warpage, although I am told that it is 'normally' not a problem, but I guess warped blocks do happen. I've also read that removal of the head bolts in reverse sequence and just a few turns at a time is important to prevent head damage. Do more searching on the forum using such terms as 'heads' etc. There are alot of posts relating to this subject. A review of all of Robyn's posts is probably a good idea as she's addressed this problem in detail many times. I'm almost afraid to put mine back together now for fear of experiencing the same trouble as you are. For us self-taught arm-chair mechanics who are especially concerned with future reliability, it might be better to go with a nice remanufactured long-block. Wish I could afford one right now.

Jerry
95 6.5 Turbo, 125K, upgraded HO dual-stat cooling, 4" exhaust, new IP, new injectors, rebuilt tranny and too many other small upgrades to mention.

[jasondmann]

Thanks for the info,

I looked at the 6.5 repair manual, like I said earlier money's tight but this may be another thing that I can't afford not to buy.

My batteries died on me before I was able to get it started with the water cross over removed. So I took apart the RH side, the side with out the dowels. I did not notice any significant damage to the head gasket but will change the gasket, get dowels and new bolts, and put it back together. If it still doesn't work then I will try the other side, if no luck after that I am going to go crazy!

On a side note, if anyone needs batteries I suggest Costco's brand "Kirkland". I know that everyone will say get Interstate but these batteries are good! I used these all winter with no problems (-30 C) and when I brought them back after the failed a load test they didn't even ask why I was returning them. Oh and the price of them went up since I originally purchassed them, I got a refund for the new price and then bought new ones with a new warranty.

I'll keep you updated, thanks for your help.

[jasondmann]

Like I said earlier I didn't see any obvious problems when I re-removed the RH head so I started to clean up the block and RH head today thinking that I would put it back together with the dowel pins and try again.

Attached are two pictures of what I found when I was cleaning the block! The second one I fixed up in paint so that you know what you are looking at.

I found a major crack in the block between the #8 cylinder, the water jacket and the hole for the head bolt.

I didn't see the crack before, otherwise I wouldn't have ordered new heads. I followed the correct torquing procedures for the head.

This crack definitely explains the problems I had but I can't see how I would have missed this the first time.

I guess I will have to weigh my options now. I cannot r&r the engine on my property (park rules, no vehicle repairs) and I am not sure that it would be the best financial decision. Keep your eyes open I may have a new set of heads for sale with new injectors and glow plugs.

Thanks for all of your help.