Flucating Temps

[Slippery Smitt]

Hello All, 1st post here.

I have a 94 GM 1 Ton Dump with the 6.5 TD, manual, 40k. While making a delivery the other day (Tue) the temp gauge went to around 230-240, then came back to naromal and was fine the remainder of the day, around 100 miles total. The next day (Wed), fluid down about 1 pint from Tue, it did the same thing at around the same distance from the house, came down and was fine. That night it did the same, then about 2 miles later it pegged and the check gage light came on, glad I was almost at the shop. Coolant was coming out the bottle and gurgling bad. Changed the cap and thermostat yesterday and bled it. Ran fine then went to get feed (empty) did the same as wed night. On the way to, no gurling or overflow from bottle, but did on the way back, approx 2 mile trip each way. Noticed this time I had coolant on the core support which led me to a leaking rad (it is now or is noticabe now, did not see any there prior to last night.) So waiting for a rad tomorrow and will change the clutch fan at same time. Water pump does not have any play or wobble.

I'm kind of thinking it's the head gaskets, but not sure. Hardly any smoke (not black, not white) when starting, but a little for approx 10-20 seconds (seems fairly normal to me), runs fine. Funny thing is since this started if you leave it sit all night, there is still some pressure in the coolant system come morning. That puzzles me as if the hg's were bad I'd think it would bleed off rather quickly. Plus once the system is bled and in operating temp, the bottle does not gurgle (or bubble) while idling. Also once it went up and then down the gauge would fluctuate some, between 170-200, not all the time though. Granted my driving since this happened has only been 2 miles while testing it.


Am I thinking in the right direction? Any tips or things to check prior to removing the heads?


Thanks
Smitty

[DmaxMaverick]

Welcome aboard!

Head gaskets fail in different ways, often progressively. You may be seeing the beginning of a typical failure, often dismissed by many as no more than a "glitch". It isn't uncommon for them to fail only at higher pressure/load, and seem normal at idle, early in the failure process. 40K miles may not seem like much, but it's over 20 years, and not likely light-duty commuter miles (dump truck). Thermostats can cause what you are seeing, but replacing it/them with no improvement points back to the gaskets. It isn't likely that a compression test will be helpful to diagnos this, but may help determine the general health of the engine, so I recommend doing that before and after the head gasket job.

[56pan]

Smitt, those are very close the same symptoms I had on my '93 C2500 6.5. I would always get bubbling into the coolant reservoir after shutdown. It was the driver's side head gasket and it finally started leaking down the side of the block on the outside. They're no fun to change and good luck.

[Robyn]

I agree with Maverick

Replace the stat and see what happens.

If the situation repeats itself then its a gasket

Most common failure points are the two front cylinders.

Coolant lays in the area in the gasket just ahead of the cylinder where there is not a passage in the block.

The gasket can erode as well as the block etches due to electrolysis

Common failure point at cyls 1 and 2

If this proves to be the case (failed gasket) plan on replacing both sides.

TIP

Be sure when you yank it apart that you keep the push rods in order with the end facing the rockers the same.

These must not be reversed

Good luck

Robyn

[Slippery Smitt]

Thanks for the input guys! Haven't had much time to play with it some more other than adding more coolant and bleed it so I can get it over to the shop. The thing that keeps bugging me is the system holding pressure. Thursday I filled the bottle up, ran it (idle), bled it added some more juice, capped it let it run some more, shut it down. Saturday figured I do the same to make sure the air was out. System still had pressure and a fair amount. It really bugs me now because of the coolant on the core support and the big wet spot on the rad on Wedensday. One would think it should have bled off rather quickly. Everything was washed off with water after changing the stat so there shouldn't have been any green stuff left that may have spilled.

Dmax, yep, the 40k doesn't meen much on one this old. Sitting kills everything. It was a mununciple truck which explains the milage. I bought it as a project truck, everything's good but the fenders and the goofy stuff thats shown up.

Hopefully I can get on it next week. Let ya know what I find.

Thanks
Smitty

[DmaxMaverick]

That may be worth another look at things. Check for cracks or other leaks in the system, such as the reservoir, radiator tanks, leaking hose connections, drain cock, etc. It seems you have a high(er) pressure leak, which may be the gaskets, but maybe not. If the pressure cap isn't new (and even if it is), I'd suggest replacing it. The radiator tanks can be replaced (reliable and inexpensive), but if the radiator is original, the core may not be suitable. Hoses and clamps should be a no-brainer (which should be routinely replaced, anyway).

If you have visible coolant leaking, at least you have a starting point, which is more than most. If it's from the reservoir tank overflow, it leads back to the pressure cap or head gaskets.

[Slippery Smitt]

Well, did the rad and C-fan, same thing. But this time I cleaned the overflow tank and could see it bubbling at idle. Got it to the shop and started ripping last night. Yep, you guys/gals be right, no fun esspecially the hydralic pump! Did see a good/bad thing, block at head down on drivers side is clean. Couldn't see it before with the brackets on.

Any inside tips? Also thinking about replacing the water pump, dampner (read they go bad on these often,) & glow plugs while everything is apart. Anything else other than the usual that should be changed at the same time? Are these head bolts reusable or get new ones? Is there a decent book out there on the 6.5 td's? Ours are vaugue on them.

Thanks
Smitty

[a5150nut]

If your looking for written information if you are a full member look in the Members Section. Lots of down loadable info there.

Head bolts are NOT reusable the are stretch to yield and are a one use bolt.

[Robyn]

When you get into the top end, the pushrods must be kept oriented with the end that goes to the rocker as it comes out.

They don't have to stay with the same rocker, just the proper end up.

One end is hardened and one is not.

When new they are marked either with a copper color on the ball or a painted band around the rocker end of the pushrod.

Lay them out as you remove them and then wipe off with brake clean and spray a little paint stripe on them.

If they get mixed up it can be tough to identify the top many times after a lot of miles.

Don't be tempted to use gaskets on the VALVE COVERS.

High temp silicone only.

Be sure to lay covers on a flat plate and tap out any distortions where the bolts were (from the engine side)

Same with pan

Do use gaskets on the timing cover along with light coating of the silicone.

This is important between the cover and the block and the water pump.

The silicone will help seal and make it easier to remove if need be.

Be sure to examine the area of the Deck where the stainless gasket fire ring sits to be sure the block does not have a groove etched into it.

A dark stain is fine, but grooves are not allowed.

A big wire brush on an electric grinder works sweet to clean the deck.


If you decide to dig deeper, keep in mind that the rods are not numbered and if you need to remove them, be sure to stamp the part lines on the outside facing side

Standard numbering sequence. 1 front left 2 front right odds on left evens on right.

Mixing rod caps is a real mess.

Mains are numbered with cast in numbers in the caps.

More info available if needed.

These engine are not hard to work on, just have a few little quirks is all.


Good luck

Missy

[Slippery Smitt]

First, Thanks to who have offer their advice and experticse!

Well, finnally got the heads off! Right side had the bad gasket in the front where everyone said it would be. 1st & last hole had cracks between the valuves, plus two precombustion chamber inserts cracked. Left side, 1st, 2nd & rear holes cracked between valuves, 3 cracked chambers, rear hole also had crack running from exhaust seat. Did not pull the heads apart or have my buddy check them, this is only from an uncleaned visual that is clearly visable.

Again, no oil or fuel in coolant bottle (or what was drained into the pan,) nothing in the oil. Should I be checking the block in any particual place for cracks? Cylinder walls from a visual looked good. Didn't know if there's some other common things to look for?

I'm looking into new heads from American Clyinder heads whos castings are made in America. Anyone had/heard anything from/about them? My buddy says thats all they'll use as no problems so far (hitting self on head knocking on wood!) Have not ordered anything till I get the decks cleaned and do a little more reseach.

Some have said about the head bolt in the back that would not come out without staying in the head. I took all mine out with the heads still in, not trying to sound to stupid, but they should go back in with the new head on right? Or am I missing something?

Also for everyone who on here or selse where said this is a total mo fo of a job, you be correct! Worst thing I ever took apart other than a heater core on a merc (think late/early 80's/90's!) The old man keeps taking things off the list of stuff we'll work on, I told him after this one, I'll take one of the list, this one. If it isn't ours, tractors only, or normal inspections and wear items when it comes to auto diesels.

Sorry for going so long and ranting a bit! Any additional insite would be greatly appreciated!

Thanks
Smitty

[DmaxMaverick]

Well, even bad news isn't always all bad. Especially when it tells you what you needed to know. There's nothing special to the rest of the job, unless you want to tear into it further. Just make sure everything goes back in the same as it came out (especially the push rods, same end up!), and when you pick up the gasket set, get the set that includes the head bolts. If not, you'll need to buy them separately. They are TTY (Torque To Yield) bolts, and they only get used once.

BTW, ACH heads are not "made in America". Only GEP/AMG/Navistar makes the 6.5L heads here, for the last ~14 years. Others may make the claim (because they may be assembled here), but the castings got here by boat. That doesn't mean they are bad, but I'll let Robyn can expand on that, as necessary.

[Robyn]

Maverick pretty well sums it up on things.

I have used heads from Clearwater cyl head in Florida.
These are new castings and the stories about the origin of the castings are all over the map.

I have heard China, Canada, South America, ahhhh Pick one as they are not made in the USA

Clearwater sends or at least did send a return ticket for your old heads when you buy a set from them.

They claim the castings are new and they machine them in their shop, then fit them with re-manufactured parts taken from used heads.

The ones I have seen and purchased looked like new parts all the way, but I can't say that this is done all the time.

The castings were certainly new and the fit and finish were great.

For the price they were a good buy.

A story I got from a reliable source claimed that Frito Lay company bought these heads by the pallet load during the years they ran the 6.5 in their chip trucks, and had great luck with them.

The set I bought were sweet with Zero issues.

As Maverick mentioned, the only new heads being cast here are done by Navistar for AM General/GEP (Manufacture of the HMMWV for the military.

No other company can LEGALLY make new heads, blocks or ??? for these engines in the USA.

Scat offers a cast steel crank, but it too is made over seas and machined here.

The AMG heads are $1000 a set last time I checked.

The Clearwwater heads were $600

Quality wise the AMG have all the best metallurgy that $$$ can buy at present.
Several major internal changes were made after AMG took over the 6.5 and these included better material in the casting and revisions in the internal thicknesses of the deck and several other areas.

This was done to reduce failures.

The AMG heads are a very robust piece and well worth the $$$$


The best thing about the Clearwater (And other aftermarket heads) is the low cost.

The castings are new ZERO DUTY CYCLES and are not hiding cracks and other failure points that a rebuilt GM head with a bazzzzzillion miles and who knows how many overheated cycles.

I had 50K on the set I used when I sold the rig and all was well.

Yesssss, doing heads in the chassis on these is a beotch.

Every one I have done I yanked the engine out and steamed it off, then went after it.

Far easier to work on and to be sure things are done right.

As Maverick mentioned BE SURE THE PUSH RODS GO BACK IN WITH THE SAME END TO THE ROCKERS.

The push rods in these engines have a hardened ball on only one end and that end needs to be at the rocker arm.

The push rods when new have a colored band on the rocker arm end near the end.
Some are about 1/4 inch wide and a tan color, others have a copper colored ball on the hard end (color wears off but traces can be seen on the outer part of the ball)

Installing wrong will result in rocker and push rod failure in short time.

Be very sure the block deck is spotlessly clean with ZERO residue left from the old gasket.

Make sure that the area around the front cyl where the gaskets stainless steel fire ring has not etched/worn into the deck.

Any dip/groove worn into the deck will require that the block be machined.

Max cut is spec'd at .010" and the new thicker FELPRO gasket used

You can cut these to .012" with no issues.

The spec is a clearance of .045" between the piston and the head with the gasket compressed and the piston at TDC.

Another area to check is the RICARDO BOWL in the piston (dip right under the pre chamber area of the head)

Look for melting and or cracking in the piston.

Any anomalies here is bad ju ju and needs attention.

Hope this helps

Robyn

[Scooby]

Ive got a couple thousand on my cylinder heads from Clearwater. No problems so far. I am getting 19 mpg since putting the new heads on. Too bad I am still getting water in the oil just like before ! I know it isnt heads, gaskets, or water pump ! Run it with water till it dies !! Turning 200,000 tomorrow.
PS- Be sure to return the old heads using the prepaid mailer they send you, or you will be charged 200. a few months later.

[Slippery Smitt]

Well, after more research, we've ordered a set of castings from liberty. China made, but, as said what isn't. My guy claims they've not had any problems with them.

Cleaned the deck off and found some bad ju ju. Some etching on the deck. Worst is on the front right. Mic'd it at around 0.0015". My guy said .002-.003 is good? Hope so as I don't have the extra dough to do a total rebuild right now.

Many Thanks
Smitty

[Slippery Smitt]

Well, got everything back and running on Monday. Started up fine and idles even smoother than before. Has a little miss in it when you first start up the road and then goes away, play with that this weekend. Hauled 3 loads of wood so far, though not many miles. Though with all I've done to this thing its the most expensive 1200-1500 miles I've driven.

Left side head was a royal pain to get back on with the exhaust man. on. Other than that, ended up being not as bad as I thought it would be. Excpet for the new oil cooler lines, that bracket is a you know what.

On the block etching, 95% came off with a hard sanding block. Then checked with a flat edge and feeler gauge, should be good. I know we've put gasers together that were worse. Hope for the best.

Many thanks for everyones help!!!!
Smitty

[phantom309]

Left side head was a royal pain to get back on with the exhaust man on.

On the block etching, 95% came off with a hard sanding block. Then checked with a flat edge and feeler gauge, should be good. I know we've put gasers together that were worse. Hope for the best.

Smitty


I 'm with you on the pass side head,. i used my engine hoist, and put in head studs,. had to tape the back stud into the head and install with head,.makes that head kinda heavy with the manifold on too,. but mine being a rust belt truck,.(something the west coasters know nothing of,.:rolleyes:) i did not want to get into an exhaust bolt removal career,...:D

A nice rough finish is good for bite for the gaskets,..

Not too many gassers i know of with 22:1 compression;),.

The stumble and skip after getting going sounds like she's letting a little air into the fuel manager maybe?,.and clears itself after it runs a bit?

good to see its going again,..