Bypass cooling for the 6.2/6.5

[More Power]

I'll say it again.....

Bypassed coolant isn't picking up heat in the heads. So, of course, the coolant will show a lower temperature.

[rustyk]

Can we have a BIG "AMEN"?!

Sometimes I wonder where these Bright Ideas come from. The only useful bypass (which most engines have) is to route coolant to the heater core to provide cabin heat as quickly as possible, until the 'stat opens...

[toyboxrv]

I don't see where you can prove that the heat is not transferring to the water. If hotter water is being used to "cool" the heads, the temperature of the head will be higher. Increasing the flow of hot water through the head isn't beneficial.

If it's such a bad idea I would expect to have seen a problem with it by now. The only thing I have seen is lower overall temps and less variance between the temps at the rear of the head versus the front. The temps at the rear of the head where water is just entering the head is lower under tow conditions. It is not because it hasn't picked up heat from the head, because it hasn't passed through much of the head yet.

Again, running the same hills with the same outside temps and the same load has shown lower temps and quicker return to normal temps. Over 100k miles of testing hasn't shown a problem.

[More Power]

The bypassed coolant should be traveling through the cylinder heads, but in your case, it's not. So, only a fraction of what should be traveling through the heads actually is.

By bypassing, the bypassed coolant will move faster (less resistance when compared to traveling through the heads), which produces an artificial lower temp where you're measuring it at the back of the heads.

If you had a thermocouple located at the mid-point inside the cylinder head, it would show a higher than normal temperature when using a bypass strategy. This is exactly where the GM engineers wanted to reduce temperatures. This is why they upgraded to a 130-gpm water pump.

In your case, perhaps you haven't run the engine at a high enough load and subsequent ECT/EGT temperature level to cause cylinder head problems. Your guess is as good as mine. I know a guy who reported 450,000 miles on his original FSD module too.

I'd love to be invited to participate in a bypass cooling test (with/without)where an instrumented 6.5 head was used. We'd use a 10K trailer, a 6% grade and full pedal for a minimum of 1 mile - longer the better. Then compare with/without bypass cooling. If the bypass strategy could show a lower temperature at mid head, I'd write an article singing its praises and I'd promote whatever vendor sells it - at no cost... Till such a time, I'm going with what the GM 6.5 cooling system engineers say about what works best for the 6.5... More flow t h r o u g h the heads - to reduce the incidence of cylinder head cracking...

The Diesel Page doesn't sell any parts for your engine. There is no financial incentive for me to promote any part (or suggest not using a part). We just want to help folks be successful 6.5 owners.

Jim

[Jason "Toby" Tobias]

I guess this is a little of subject, But does anyone no if the 130 gpm water pump will bolt directly to a 1994 truck?

[More Power]

The 1996 and earlier factory 6.5 water pumps were rated at 87-gpm, which were designed to operate with a single thermostat.

The uprated 1997/98 130-gpm water pump is a direct bolt-on, and your existing fan-clutch will bolt on. We recommend using the twin thermostat setup as well. Several vendors sell the complete kit using all genuine GM parts.

The uprated water pump is also available in the 1999/00 style, which contains an integral water pump pulley that includes a threaded fitting for a screw-on style fan-clutch. Whether 1997/98 or 1999/00 style, each produce 130-gpm at 3000 engine rpm.

These are not "heavy-duty" water pumps. They are "High-Output" water pumps. Only the 1997/98 style water pump is marked "HO".

Jim

[phantom309]

wonder why the australians are so fond of this mod ? something about steam pockets, steam bubbles and cavitating water pumps,. so more flow works better,. they run their stuff in the desert,. and when the pump is pumping water around the block thru the heads and also thru the bypass lines, if it comes to a closed thermostat, then the water gets sent around again, till it is hot enough to open the t-stat,. the theories mentioned here seem to be based on the water heading straight back into the rad,.
australians also drill the fire deck in the spots needed to increase the flow up thru the head,.
"soak" time is not the best way to remove heat, "flow' works better,.
JMHO,

nick