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What years have what 6.5L cooling?!

88gmctruck

88gmctruck

02GMCtruck
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Auburn, Wa
Ok, so I've read a few threads, articles and just recently the EPC.

I'm confused what setups were available and what setup my 99 has (as it appears to be a mid year thing). Mostly I was reading that 2000 trucks all have the same waterpump high flow, balanced waterpump.

According to the EPC and my RPO breakdown, I should have that same waterpump (gm shows it available from 99-00)

In 99, there are two part number's listed for water pumps.

Part number 88894036 / ACDelco #251-590 for 6.5L trucks with RPO ZK3 (pull ahead design) and MT1 (4-speed Automatic). This Pump was used on all 96-98 6.5L trucks with dual thermostats. It was only used on 99 trucks with automatics.

And

Part number 88894035 / ACDelco #251-603 for 6.5L trucks without RPO ZK3 (pull ahead design). So this one was used on trucks with manual transmissions in 99.

In 00, there is one part number.

Part number 88894035 / ACDelco #251-603 for all 6.5L trucks.

So I'm assuming I have the latest Gm waterpump. Is there any other way to tell?
 
What's the deal with the bypass fitting? What year was restricted?
 
It's the spin on, 9-blade fan.

Is the coolant flow balance thing the hose that runs from the bottom of the crossover to the top of the waterpump?
 
Heatercore to where?

As I said before, the latest style waterpump said it was available in 99-00, and according to the EPC in 99 it was installed on trucks without the RPO MT1 (4-speed automatic) which I obviously don't have. This truck, aside from the gooseneck was BONE stock, i doubt it was ever touched.
 
To my understanding.....which is sometimes skewed..... If you have the spin on fan clutch, you have the latest greatest version.

Now, I may be wrong as this "restrictor fitting" may play into the mix too....
 
Ok...

So I have this style fan clutch, just to clarify.
365--20100505093120.jpg


I have a hose between the crossover and waterpump. One from the lower radiator to bottom of puke tank, another from the puke tank to the top of the radiator, one from the radiator to the heater core and one from the heater core into the side of the crossover, into one of those pushlocks.
 
According to the EPC the crossover is the same on all dual t-stat housings.

Maybe it's something in the waterpump itself?
 
ak diesel driver said:
IIRC it's the one from the crossover to the heater core
Click to expand...

The quick connect ?
Most people lose those and use a regular fitting.

To answer OP yes, if that is the clutch you have , you have the best WP. Supposedly anyway. IDK. My 98 has has the 4 bolt and it cools just as good as my 2000.
 
Ok, excellent. I was reading on another thread that only 00's had that style clutch/WP, which is why I researched and asked the question. For some reason in 99 automatic trucks kept the old pump and clutch while the manuals got the newest stuff. Interesting for sure.
 
It is the fitting on the water pump between it and the crossover thermostat housing. The restricted fitting is not so much for balance as it is to stop as much hot water from bypassing the radiator and going right back into the block. This fitting is recommended on any dual thermostat vehicle, or any single stat if you do not use a bypass blocking thermostat with the stem and plate sticking out the bottom of the t-stat. The balance comes from the wheel/blade and passage design.

Any truck with a thread on fan clutch has the latest water pump. The other pumps (not as balanced) have a 4 bolt on fan clutch interface to the water pump.
 
I can't find any different fittings between the waterpump and crossover on any dual thermostat equipped year, they are all part number 10183956 for the top and bottom. Crossover's are all the same too, 12553405.

Any pictures of these?
 
They were not originally eqiupped with the restricted fitting. Although I have seen it at the dealership and they were aware of restricted bypass fittings available for several year trucks.

The crossovers are all the same for 97+, different in 96, and different in earlier years, different on HMMWVs.
 
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