Help with 5.3 LS water pump

[Flysocal]

My crate engine is a 5.3 1999+ vintage. I understand there are 2 different water pumps for these trucks 1999-2004 (what I have) and newer. Not sure when the change happened maybe 2005? Anyway, looking at pics the water neck spout appears different on the newer style pumps which might help me. My radiator hose would be much easier to figure out if I had a newer style pump I think. Also my thermostat housing might be an issue right now. Got a MR gasket swivel housing and its description said 2004+ LS engines. Called Holley and they said I'm good to go but I'm not convinced. When I install the housing in a newer style (corvette) water pump the thermostat and housing bolts up with ease. When I bolt the same Mr gasket swivel thermostat housing into my truck water pump there is about 1/4" thermostat spring compression needed to make it fit. Doesn't seem right to me! Anyway I'm looking for some insight here. Would a newer truck water pump solve both my radiator hose and thermostat problems without creating a couple more? If so, is there any company that sells newer style truck pumps with threaded NPT heater hose hookups? Save me a trip to the machine shop!

[Flysocal]

Here is what the new style pump looks like.

[mongocanfly]

My 02 has the curved neck fitting and my 13 has the straight neck like your last pic..for what its worth my ls3 neck points straight at the radiator on the drivers side of the pump..
Curious..why the threaded heater hose fittings

[Flysocal]

Is there a difference between the 02 and 13 besides the water neck? Have you noticed a difference in depth at thermostat housing? Like I said, Holley lists its thermostat housings as 04+ and I don't know why. Just doesn't seem right to compress thermostat spring. As for NPT fitting for heater hose that's no biggie but it would be nice to match up fittings with vintage air bulkhead

[mongocanfly]

I changed the pump on the 02 so i can look at it close..from the back of the housing to the thermostat surface is about 2 3/4"..the thermostat seating depth on the inside is 1 3/4"..the 13 measures the same from the back of housing to thermostat surface..same as the 02..they look identical from the outside..never had the 13 apart so I don't know what the thermo looks like

[mongocanfly]

Oreillys shows the 02 thermo fitting up thru a 05 5.3...it comes pressed in the water neck...when I pulled up the 13 it just shows the thermo by itself..so there may be some difference..

[Flysocal]

Very cool thanks mongo. I'm gonna call mr gasket and ask why the housing is listed as 04+ . Also waiting on some radiator hose and will see how it fits. A newer style pump might solve my hose routing issue and ease my mind on the thermostat! The spring compression doesn't seem right. I'm thinking the new pumps have a deeper thermostat housing chamber.

[dwcsr]

We used the stock outlet on the bottom and I think a truck water pump but it was a 2013 engine and the radiator was made by Walker for an LS

[Coupeguy2001]

I have a 01 tahoe. The thermostat went bad, and the pump was leaking, so I went to O reilly's and got a new thermostat and pump.
The pump went in perfect, and the thermostat was easier to install than the original was to take out.
I read in my manual that there are two different types of thermostats, early and late.
I compared the photos, and I got the late one. I removed it and took it back, and exchanged it for the early model.
What I could determine was that the early thermostat sits in a well in the pump, and the spring pushed against a machined diameter, with the center hole in the thermostat doing a little bypassing on a cold engine.
The later thermostat sits in the pump and rests against the housing machined ring, and the thermostat opens up similar to the ones in a smallblock.
The indication that something was wrong was after the pump change, it wouldn't warm up past 167 degrees, and the engine computer flagged that the temp vs time calculation indicated a problem.
So with the right thermostat (early in the 01) , everything works like it did when it was new.

[Flysocal]

Originally Posted by Coupeguy2001

I have a 01 tahoe. The thermostat went bad, and the pump was leaking, so I went to O reilly's and got a new thermostat and pump.
The pump went in perfect, and the thermostat was easier to install than the original was to take out.
I read in my manual that there are two different types of thermostats, early and late.
I compared the photos, and I got the late one. I removed it and took it back, and exchanged it for the early model.
What I could determine was that the early thermostat sits in a well in the pump, and the spring pushed against a machined diameter, with the center hole in the thermostat doing a little bypassing on a cold engine.
The later thermostat sits in the pump and rests against the housing machined ring, and the thermostat opens up similar to the ones in a smallblock.
The indication that something was wrong was after the pump change, it wouldn't warm up past 167 degrees, and the engine computer flagged that the temp vs time calculation indicated a problem.
So with the right thermostat (early in the 01, everything works like it did when it was new.

This is what I suspected. I ended up buying a new style pump because of the outlet direction. It also comes with the thermostat so I will remove the Oem stat from the housing and install mr gasket swivel. I also plan on tapping heater fittings to run AN fittings to bulkhead.

[Coupeguy2001]

Be sure to use stainless fittins both on the hose and the pump. I had a 63 Nova SS with a 327, and I used AN fittings. One day, it wouldn't run right.
I pulled over, and watched the pinhole in my ALUMINUM fittings spraying the distributor, intermittantly shorting out the coil and distributor.
I wrapped a rag around the bad fitting, and went and got stainless stuff, and no more problems.

[mongocanfly]

Good info on the thermostats coupeguy..I didn't know there were early and late ones..

[dsraven]

this info is from the corvette forum.
hope it helps smebody. sorry it is a bit late for this one.


On the LS engines there seem to be 2 different thermostat designs an early one where the thermostat is made into the thermostat housing 97-late 03/early 04...

And the 2nd design where the thermostat is separate from the housing 03-04/ to current....
OReilly auto parts....

early thermostats........(housing and thermostat 1 piece)

160 DEG part # 37960 $29.99

180 DEG part#37980

187 DEG part# 37987


later type......separate thermostat

160 DEG part# 6367 $18.53

180 DEG part# 6368 $18.53

195 DEG part# 6369 $18.53

[dsraven]

here is a link to the engines section here that has some pics.

http://67-72chevytrucks.com/vboard/s....php?p=6106458