Removal of theoretical cooling #8 & #6 cylinders mod

[john8662]

I have a small dilemma that I want opinions on, pro and con. First off I have the 97 cooling mods on my 95 K2500 burb. Prior to the install (when I got the burb and didn't know any better) I consulted with a good friend and owner of a local diesel shop about 6.5 cooling. He and I had talked many times about what goes wrong on some of the 6.5's that he had gotten to work on in the shop that had knocks and bad engines. He said that most of them went bad as a result of the #8 cylinder getting too hot and galling. I talked to him many times about what could be done to prevent that from happening. His solution that he had been installing on many early (92-95) 6.5's was a heater hose passage to the passenger side cylinder head. All this consisted of was a piece of 1/2 heater hose, two nipples and a plate for the passenger side head (a plate like whats used on a 6.2 glow controller cigar-style or inhibitor switch). I didn't tow with my 6.5 at the time and didn't really worry about cooling that much so I installed this mod on my 6.5. The plate is installed on the passenger side rear head and gets a nipple installed into it. Then attach the heater hose to the rear of the head and connect it to the extra port on the water pump by installing a nipple in the extra port. It looks like this when installed:






The theory behind the mod (whether it works or not) is that it gives the coolant in the hottest point in a GM head a passage directly do the water pump and to a cooler part of the engine or radiator. This mod in theory (without actually looking at where things flow) could allow this area of the head to cool better and better cool the #8 & # 6 cylinders nearest to the hot turbo system. What direction would coolant really flow in this idea?

Later on I got to reading on TDP about 6.5's, I hadn't paid much attention in the past to anything pertaining to 6.5's as I had a 6.2 at the time and never wanted a 6.5 for all the problems I had heard about them. But since I purchased one (I wanted a TURBO DIESEL) I really have enjoyed it and learning about it, I should have gotten one sooner. From my reading on 6.5's I learned that you could upgrade the cooling system to the "97 cooling mods" by replacing the water pump, thermostats, etc (you've all heard it before.) That

[Barry Nave]

This sounds like something for the guys who still run the single stat.
I do wonder though if that hose even flows any water Looks as though it would be nothing more than a Balance tube.
Knowing the cooling up grade allows more coolent to flow,around the block as not to allow hot spots.I,m thinking only about 9% more flow through rad. is upped yet more flow around block is whats as important.
I'd would pull it out for fear it may cause the up grade to degrade
Still the ? as you state, How or if there is any flow through that hose and what diweck-son
Just went out to look at the water pump. That port would seem to be a return like the other top side from cross over that takes the flow back to the block. So it would seem as though your pulling coolent from that area, 6&8 and taking it back through the block,as is what the cooling up grade is doing. May be now taking to much hot coolent back through the block and not letting it go to the Rad.
Now take this ideal on a single stat,with a high flow thermastat and a high flow pump and you may have something going on.
Can't what to see this thread go

[ 02-22-2004, 02:36 AM: Message edited by: Bnave95 ]

[gmctd]

Several types of infra-red laser spot-temperature digital thermometers are available.

I would take measurements back to front on each head, starting at the rear block-off plates, then between the intake ports, then the outlets into the coolant cross-over.

Do this with engine at normal temps, at idle and cruise rpm.
Block off radiator air flow, so temps rise, fan clutch is fully engaged, take the readings again, same spots, same rpms.

Block off the mod hose with vise-grips, take all readings again, same method, same coolant temp ranges.

Removes all guess-work, gives a reliable base of information.

Would get better readings on the exhaust side, but the turbo manifold is a major restriction.

[grape]

I asked over a year ago about running those outlets up to the crossover behind the thermostat. Works on hot rod 700 horse gas engines but was told here it wouldn't work on our complicated 200 horse diesels?????? go figure.

[john8662]

Thanks for the replies, keep em coming.

GMCTD, I like your idea of testing if it really does any good by eliminating it from the system for a little while (penching it off) and seeing temps, and the using it and measuring the temps. If I get something to measure the temps with I'll give it a try. How much do you think a laser temp measuring meter like you were describing would cost me, and where would I get it?

Bnave95, I also wonder if what you were saying is true also, that this flow of water is only throwing hotter coolant from the # 8 & 6 area back into the block. This wouldn't necessarily be a bad thing just that it could effect the effecientcy of the cooling system. This could add hotter coolant to an already warm/hot area into the block to mix with the other yet cooler coolant.

I still have the mod in place, weather it does any good is what I'll need to find out.

Main thing though, is this sort of mod helping or hurting the cooling capacity of the engine, with the 97 HO cooling mods in place?

[Tom C.]

There is a site that sells aftermarket items for Hummers. They have a cool kit for the 6.5 TD that feeds extra coolant to the rear of both heads via the "inspection plates" at the rear of each head. It would be very simple to make for a fraction of what they are selling it for. If you want to take a look email me at me2howu@yahoo.com and I'll send you the link.

Tom C.

[Barry Nave]

Hey Tom, post the link here

[toyboxrv]

If you're expecting that the pump will push more water to the rear of one head, I would doubt it can. The two inlets from the pump to the block are slightly larger than the two outlets going to the thermostat housing. I had installed a temp gauge at the rear of the passenger head and found the temperature to be as much as 20* higher by the #8 cylinder during towing on hills. I bought 2 of the same plates you have and ran hoses from them to the engine side of the thermostat housing. I immediately noticed a significant drop in temps during the same situations. I posted on here about my mods, but was dismissed by most as having created more of a problem than I was solving. Despite everyone else's opinion, I still stick to the effectiveness of this mod.

[Kidd]

I picked up a laser infrared temp meter at my local parts jobber for about 100 bucks. The laser shows exactly where you are reading temps.
K.D.

[mhagie]

To add to the confusion I have a 93 6.2 block bored to 6.5 specs w/Banks Turbo, At rear of right head I installed a temp sender (Nordskog) digital temp gauge from Summit racing.
I just installed it late November and only managed about 50 miles on it before retiring truck for the winter,during the time I run it the digital temp gauge never exceded 170* this is with a 195* stat and factory dash gauge reading a tad shy of 200*.
One of these days I plan to remove sender and heat it in a pan of water to check accuracy cause I can't believe that the back of the cyl head is running cooler than the center where the factory temp sender is located.
To make matters worse the glow plug temp switch is located on rear of left head and it is acting funny also, it is supposed to open at approx 150* so glow plugs will not operate above that temp, but when I drove it last at normal temp on factory gauge the glow plugs still cycle so the temp switch is not breaking contact.
Every sender on the engine is new so now I have to figure out which is the bad one.
The fast idle switch does work droping idle down around 100* recorded on the digital gauge.
I am tempted to dump the digital gauge for a 2 5/8 mechanical gauge cause I believe its accuracy is in question here, I never did like electric gauges, but that green Led does look really cool.
Thoughts?..........Merle

[gmctd]

Thanks, K.D. - I had thought they were still up around 200.

The tap used in the modification is on the intake side of the water pump, so the coolant drawn from the rear of the head would be recirculated along with coolant drawn from the cross-over bypass.

It might require enlarging the coolant passages in the head gaskets to be really effective.
The passages are gaged small at the front, increasing in diameter towards the back to meter block-to-head coolant flow.
This is due to increasing frictional drag as the coolant must flow around the cylinders on it's way thru the block.

A laser spot-check would tell the tale.

p.s.

Merle I'd stick the digital sender in various places in question - rear head, front head, cross-over, etc - to get an accurate reading.
It probably won't be off more than a degree or two, and might set your mind at ease as to what's actually happening.

[ 02-22-2004, 07:09 PM: Message edited by: gmctd ]

[ANXIOUS-SUBMAN]

Please be aware that the lazer pointer on those infrared meters is just that, a pointer. The meter is not just indicating the temp at that small point of light but instead the lazer indicates the center of a much larger area from which the temp is averaged. These are optical divices and so the farther away from an object you are with the meter the larger the area that is averaged. I've watched people in the plant point these things at a steam pipe 20' over their head thinking they are only getting the temp of the pipe cuz they have that little lazer on it when they are actually getting the average temp from about a 10' circle around the pipe. The brochure for the Raytek MiniTemp has a good illustration of how these work. Raytek MiniTemp

[john8662]

Tom C.,

Would you post the link to the Hummer cooling upgrade, so that we can all see what you're talking about. I would be interested if it is plumbed similar to what I have installed and what they back their product with. Whether they have any proof that this type of mod does better cool the suspect area of the head.

GMCTD, you bring an interesting point that if the ports in the heads are not very large that the existing cooling system is probably more than sufficient to push enough coolant though the passages anyways. So, in conclusion, that would mean that the mod wouldn't do much good anyways, without the enlargement of the ports in the heads and gaskets.

I'm a little strapped for cash, so I don't think I will be able to get a digital temp meter any time soon, as I would probably put the money in other upgrades. Anyone want to lend me one for testing? Thanks for the replies! Still haven't decided whether to take it off or not.

[Barry Nave]

John
Sounds like it's not doing any harm,maybe some good and may be not. Like to be more work still ahead. Hummer has it so it's been done. More pluming to work around
The cooling up grade,the updated fan and clutch seem to be the ticket for the 6.5 with added HP.
I'm one that needs my truck to last for ever New trucks are out of the price and I know all I have done to my truck to make it live.
Some of my jobs the owner thinks the truck is new and not a 95.
So any ideals I can pick up on I'll use

[C.K. Piquup]

I wunder what a little radiator would do for that extra hose(like a section of baseboard).

[grape]

what I'm doing next will blow your minds. I'm mounting the double stat housing on the rear of the engine with the hose outlet pointing forward on the pass side. Using the bypass on the housing to go to the heater core, then connecting the front therm housing holes to the water pump bypass with a t just infront of the injection pump. This ought to be interesting. At least I won't have to butcher the housing for the mechanical injection.

[gmctd]

When I first stumbled across the dual t-stat cross-over in a boneyard, without knowing exactly what it was, that was my first thought - mounted at the rear of the engine, hose outlet facing forward to the radiator.

Motorhome? Stationary? What?

Then I checked the coolant passages thru the decks in a bare 6.5L block, and knew that was not the purpose or correct location.

It was a neat piece, and for only $5, so I bought it anyway.

Fortuitous move!

A short while later, I saw More Power's coolant upgrade article, and there it was.

Long, slow pitch before the fast curve.......

Point being - if you have not, you might compare the deck passages to the restrictions in the gaskets, see what you think about front-to-back flow thru the block, parallel flow block-to-heads, and back-to-front flow thru the heads in oem configuration.

Seems to me, decks and gaskets will require some modification, particularly for the turbocharged engines.

Anyone with further thoughts?

edited for content, to fit time allotted, and for screen width.

[ 02-23-2004, 12:37 PM: Message edited by: gmctd ]

[john8662]

OK, so it looks like no one has really a reason why it shouldn't be on there, that possibly it could give a small margin of added cooling to the hottest part of the engine. For now, I'll leave it until proven otherwise. Only weird thing is if I have to take this rig in eventually for an in warranty pump replacement, the mechanic will have something to poder about, as well as the other upgrades. Anyways, eventually I will need to borrow or eventually purchase a digital laser temp meter for further testing. If I can test it, then maybe I can prove that it does help, even for an already upgraded engine. Thanks for the suggestions and ideas!

[toyboxrv]

It would work better if it took water from both heads. Since both are hotter in the rear, you should be diverting an equal amount of water from each head to balance the flow.Drawing the water into the pump would recirculate it into the engine, whereas putting it into the thermo housing would allow it to go to the radiator to be cooled.

[ucdavis]

Couldn't tell you if its good, bad or indifferent for cooling. But i'd suspect it is hard to purge the air from that tubing sinc it represents sort of a high spot in the assembly; so if you are using DexCool or equivalent "permanent" anti-freeze, the more rapid oxidation from air entrained in the high tech coolant could be an issue. The early radiator/coolant failures on GM v6's, IIRC, were from not getting the air properly bled from the system.
Just my $.02.