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The Hummer Knowledge Base

Transfer Case/External Cooling Pumps

External Cooling Pumps. The Carter is on the right and the Tilton is on the left.

Tony: The Tilton pump works for many others, so you must have other problems such as restriction or pump failure. What are the specs on the Tilton? Do they match what I have stated so many times? 2 gpm at 50 psi and capable of 300 degree ATF?

Michael: Tony --I am glad you asked. The actual temps quoted by tilton are 265 degrees. The pump however is made by FlowJet, Tilton only modifed the housing. The polypropylene housing is rated at 130 degrees and uses elastomers of Santoprene and Buna. The Nylon are rated at about 160 max. The guy at flowJet didn't think it was a good idea to go 100 degrees over their rated temp max. It was confirmed by him that this pump is a diaphram --+ displacement, puller type pump. It actually presents a pulsatile flow by the bouncing of the 2 piston heads as they wobble in the valve body. Some have mentioned again that the pump can really be placed anywhere in circuit--perferably after the cooler-to keep it coolest. The Tilton guy stressed that 1/2 hose should be used to maximize the gpm. With 3/8 hose the flow is probably less than 1-2 gpm, maybe less than 1 gpm.

FlowJet has a similar 4000 series pump 4300-506 that has a Quad piston head with a GPM of 4-5, at 35 psi with pressure protection. It uses 3/4 hose, a puller, rated for Carbon Based products and Diesel, Geolast capable of 6-8 ft of lift. It is rated at 14 amps--this thing would probably shake the vehicle more that the engine. Again--it was advised to watch the filter resistance. It's self-priming, can run dry, ball bearing drive, there are 2 cams available. There is a model with 1/2 barb. It is cheaper than the tilon at less than $150 if you wanted to try your luck with the temps.

Tony: From your pictures, the Tilton and Carter both appear to be diaphragm-type pumps.

Michael: The carter is considered a centrifugal pump. The center part or head just spins and throws out slotted rectangular plates to seal against the outside of the chamber. It has a nice sound when it is spinning. The fluid runs in a vainlike channel. Of note the screen it comes with is really for gas--I would take it out completely. I tested it without--the dextron in mine did not circulate.

Tony: I can only guess that the diaphragms are nitrile (buna, NBR). Most nitrile formulations are only good for 275 degrees maximum. Some fail as low as 180 degrees. If the diaphragm is nitrile, I would only recommend these pumps be used after the cooler and/or that they be run frequently enough to make sure the fluid temp the pump sees is below 220 degrees.

Michael: That has come up a few times now.

Tony: Also, if they are diaphragm as they appear, both of these pumps should have internal check valves to control the fluid flow. They should not drain back to the transfer case and a check valve in the loop should not be required. I can't verify this for sure by the pictures, but it looks like they have check valves and I've never seen a diaphragm pump without check valves. If the check valves leak, flow would be reduced also.

Michael: I don't see anything that resembles a check valve. The tilton has 4 small, flap valves which may act as a flowback valve, but primary function is probably to direct the flow in the right direction.

Tony: The human heart is a diaphragm type pump. I would think you would understand the function and limitations well. Yes, this is a slam. Sorry, couldn't resist. There must be a flaw in my human nature.

Michael: You have found the reason for my compulsive interest in this subject. An Occupational hazard type of thing.

Tony: Again, I would try to use a mechanical pump. You like Grainger, so a Grainger number 4F652 will work fine. This is a Barnes hydraulic gear pump, .194 cubic inches per rev. Bi-rotational (swings both ways). Appears to have a stout shaft bearing to handle the pulley side loads. $114.25.

Michael: This certainly seems like overkill. For intermittant use I was hoping to just use a 12 volt unit, but it seems like there are many more solid, stable units at higher temps available in mechanical units.

Tony: I certainly hope this answers your "last time" questions. This really isn't fun anymore.

Michael: Sorry you feel this way, Tony. Your efforts are truly appreciated. At least from me.

The cleaned up Tilton pump is really a solid piece. I first tested the pump by putting on a 4 ft 3/8 line from Dextron container to the intake of pump. Came off the pump with 10 ft of line back into the container. Good flow.

Next added a 3 ft line to the outlet of pump to a Magnafine filter then to my 10 ft line back to container. Immediate priming and good flow. I then started altering the height of the inlet and outlet lines. Absolutely no change. The core of flow coming out of the hose was completely consistent.

I guess next would be to start adding a cooler.

Michael Selig

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