6.5 Engine Cooling Solutions

[More Power]

As we head into spring and the summer towing season, more 6.5 owners are reflecting on the cooling system challenges they may have faced in summers past. We've made available a couple of important articles from years past that discuss these challenges, and offer solutions.

<a href="http://www.thedieselpage.com/members/features/fanclutch.htm" target="_blank">6.5TD
Fan-Clutches
Engine Cooling Solutions</a>

Cooling the 6.5 requires a systems approach. We've talked about the importance of a clean radiator, 130-gpm water pump/dual thermostats and other system components that improve engine cooling. One often overlooked (but equally important) component in the cooling system is the ubiquitous fan-clutch. We installed a custom 6.5 fan-clutch on our 6.5TD Project engine in June of 2001, which was designed to engage sooner and improve engine cooling. This gave us an opportunity to evaluate this fan-clutch through an entire summer towing season and consider its effect on engine cooling. Go here to learn more about fan-clutches and their how they operate. This article appeared online in spring 2002.

We also produced a comprehensive article in 2002 titled 6.5 Cooling Solutions that defines and offers additional solutions for the cooling challenges many owners face.

MP

[autocrosser]

I just pulled the grill to change the orfice on the A/C and clean the trash out of the coolers and condenser. The condenser area behind the aux coolers was completely blocked. I vacumed it and then hit it with a pressure washer to blow it all out. Well worth the time spent.

[tanker]

Often overlooked is the heat transfered to the cooling system from the transmission cooler lines. I installed 2 additional coolers on my 95 6.5 suburban. The best is a 12-volt fan cooler mounted under the floor, this will drop temps 70+ degrees prior to the radiator cooler.
As "More Power" stated above a fan clutch that engages sooner than the GM stock clutch works wonders. My A/C never cooled very well from new, but adding John Kennedy's clutch and composite fan made the A/C work excellent in the summer when in traffic. It really moves some air.
Each year or so, pull the radiator and clean it out of all the bugs and debri that gets into the fins, I also ran a bug screen to keep most of the critters out of the radiator.
Watch your pyrometer, and back off as it nears 1100 degrees pre-turbo.
All I can say is heat kills almost anything, man or machine. Keep it cool.

[DA BIG ONE]

I have been considering the crossover setup for the rear of the cylinder heads, ports are already there for this mod and it is explaned here http://www.humvee.net/hid/engine/ the look under "cracked blocks".

I wonder why GM never offered this option?

[JohnC]

Originally posted by DA BIG ONE:
I have been considering the crossover setup for the rear of the cylinder heads, ...I wonder why GM never offered this option?

Do a search in the topic. It's been discussed before. To say the least, there are differing opinions on it's value.

[Craig M]

Looks like a very simple install. You could remove then tap your existing covers, get a couple of hoses made up and do this on the cheap.

[DA BIG ONE]

Originally posted by JohnC:
</font><blockquote>quote:</font><hr />Originally posted by DA BIG ONE:
I have been considering the crossover setup for the rear of the cylinder heads, ...I wonder why GM never offered this option?

Do a search in the topic. It's been discussed before. To say the least, there are differing opinions on it's value. </font>[/QUOTE]I did a search here and found nothing, any hints that can help find it?

[DA BIG ONE]

Originally posted by Craig M:
Looks like a very simple install. You could remove then tap your existing covers, get a couple of hoses made up and do this on the cheap.

I am actually considering this route, keeping the cooling hoses the same size as the heater hoses. Tap for, or weld fittings easy, easy, thenwith the savings I can take the little lady out to a nice dinner.

[More Power]

I spoke with Bill Heath a while back, and was surprised that he had experimented with the rear coolant flow idea, and even developed a parts kit to accomplish a conversion.

Frankly, I'm highly skeptical about this approach to better cooling, but am open to changing my mind if I see some convincing data. I've studied the coolant flow paths through these engines, and (at this point in time) believe taking coolant out at the back of the cyl heads will result in higher cylinder head temperatures at the front.

Properly instrumented heads would provide convincing data, one way or the other.... We'll see.

MP

[JohnC]

Originally posted by DA BIG ONE:
I did a search here and found nothing, any hints that can help find it? [/QB]

Try This thread

[mhagie]

I am considering the rear coolant kit.
The compelling reason is that I have found that air is trapped at the back of the heads, because I tried to install a mechanical temp gauge at one of those ports and I could not get a true reading because of trapped air at the back of the head causing erratic readings.
I am thinking of using the AN -04 size hose which is 1/8 pipe and should be small enough to release any trapped air but not too large to interfere with any flow rates.
I don't think too much of the heater hose Tee so am thinking of tapping the crossover housing close to the heater hose outlet.
I seems to me some DP member has tried connecting a hose between the two rear ports but can't remember their results, good or bad.
Merle

[damork]

I've tried rear cooling kits on older diesels from GM (6V-53) under extreme heat conditions and it was a miserable failure. These tests were done in the Sahara and Persian Gulf.

Some theories to leave the thermostats out were also a disaster in the 2 cycle Detroit diesels as well as some Cat engines. Leaving them out caused hotspots in the back of the heads because flow was taking the path of lease resistance and not completely flowing through the heads.

Cooling paths in these engines have taken years to develop and most of the time the people that design them have done a good job.

[tom.mcinerney]

OK,
If Merle got air there, that justifies a little bleed...

Related question:
When discussing replacement of the leak-prone heater hose/tube termination , Damork suggested going to the GM dealer, and procuring a nipple from a 6.2 , as that incorporates a designed-in restriction {then a short length of hose suffices connecting to the tube, which has been trimmed}.

What is the purpose of the designed-in restriction here?? Is the consideration a quick warmup ? Presumably both the engine and heater would warm faster in cold temps with an optimal restriction.

[DA BIG ONE]

It appears then there is no real data, on ya or nae with this mod.

Water wetter will surely help, but it will find a way to exit a cooling system that is not in perfect condition.

I did notice the hummer guy said the crossover does even out temps, but in the equasion is the hummers engine compartment and drivetrain tunnel which sux when it comes to airflow our trucks have much better airflow through these areas.

I guess I will get in touch with Bill too and get his input.

Any of you know if those water jacket ports are used on marine applications? Then wonder if there is as much failure w/cracking in marine applications?

[mhagie]

Since I can't remember the exact problems I had with a mechanical gauge in the rear crossover port I will do it again so all will know.
Right now I have the factory temp sender in the factory location in the left head, I have a mechanical gauge probe tee in the crossover/thermostat housing prior to the heater hose outlet nipple and a 195* stat.
I can remove the glowplug controller and install a Nordskog Digital gauge that I changed out cause If the sun shined on it I could not read it.
This way I can sense temps from three locations and REALLY confuse matters.
It seems to me that at the time I had the digital in the left head and the factory in the right rear crossover and it was reading temps around 210*plus altho its hard to say with the factory gauge, all w/195 stat.
This engine is basically a 599 6.2 block bored to 6.5 specs with 84 6.2 accessories.
Merle
PS digital gauges oil & temp for sale

[Cowracer]

From what I see, this kit TAKES water out of the heads at the rear. Probably not good.

Has anyone ever thought about ADDING water to the heads at this point. On our circle track cars when we ran 406CI motors (400 SBC .030 over) we had a terrible time keeping them cool.

One engine guy came up with a deal that drilled and tapped a ~1/4" hole in each "arm" (outlet port) of the water pump and attached fittings and hoses to that location to take cool water directly to the ports drilled and tapped into the heads. It worked pretty darn good, too.

Tim

[HammerWerf]

Folks,

I currently have a temperature guage plumbed into the glowplug controller spot on my 1983 CC.

The controller died, and I took the opportunity to see what the water temperature looked like

back there above #7 cylinder. I installed the gauge in early Feb. just prior my taking a trip to LA

over the Grapevine on I-5. I knew that this would be the quickest way to see what kind of

temperatures the engine produces in the back of the heads. GMCTD had an excellent post on

the 'Place' about the internal flow characterists of our heads. GRAPE too, asked very good

questions and posted solutions that I think are possible to implement, how, I don't know yet. They

got me to thinking about the idea of shunting water from the back of the head to the heater line,

like the hummer guys proposed.

Bit on the engine. A MR. Goodwrench replacement by the previous owner, single 195F

thermostat and stock water pump(66gpm?)

Average trip temps were in the mid 50's for the trip. Here is what I can remember at the moment.

Shotgun rider recorded data at the time including altitude. Will transcribe and post later.

At speed up to 45mph, the temp difference was 20F back to front. Front was 195F and the

back was 175F.

From 45 to 60mph, the difference was 15F. Front was 200F, rear 185F.

At 60 to 70mph, the difference was 10F. Front was 215, rear 205.

I has just cleaned the bugs out of the radiator, and the A/C condensor was removed at the time of

the trip.

I still have the gauge installed, awaiting warmer weather.

On another note, I have found an ad in "Drive Magazine" ( caters to the Hot Rod set) for an
outfit in PA that sells a kit to modify the oil pan so you can take off the sump without taking the whole pan off. Kinda like a DuraMax. Might be of use to monitor some of the motors being

built. No web page, but I will post the Name and phone number.

HammerWerf

[ace58]

While changing engines, I drilled and tapped the plates for either -6 or -8 hose and fittings, installed a tee between lines from each head and extended line down to rear heater connection hose at passenger side of transmission. A real clean installation with great results. This allows coolant to circulate evenly up through block.

I had been sent a link to the hummer mod site about a year ago, but it seemed like a lot of money for what they were offering.

[DA BIG ONE]

Originally posted by ace58:
While changing engines, I drilled and tapped the plates for either -6 or -8 hose and fittings, installed a tee between lines from each head and extended line down to rear heater connection hose at passenger side of transmission. A real clean installation with great results. This allows coolant to circulate evenly up through block.

I had been sent a link to the hummer mod site about a year ago, but it seemed like a lot of money for what they were offering.

I see it is a 1999 truck, how about letting us know why you had to change out the motor, what is the engine code of the bad one, how about truck build date too?

[JohnC]

It would seem to me that the numbers posted by HammerWerf do not support the idea of a hot spot at the back of the heads and further imply that taking water from there would increase temps in the front. Am I missing something?