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As it's begining to heat up in Georgia my 1988 Comanche 4.0 is starting to show over heating issues. When I first bought the truck the heater never worked very well. I did a cooling system flush and blew out all sorts of chunky brown stuff. I was fully expecting to have to replace the radiator and heater core at some point. It looks like that day has come. Lol While I'm changing out parts I figured I may as well upgrade and do some preventive maintenance; converting to an open style, replacing mechanical fan with electric fans, changing heater hoses to the newer 97+ style and getting rid of the RENIX tank and heater valve assembly. I'm sure it still has the original water pump and is due for a replacement. Which water pump do you prefer; original ($40), flowkooler ($80) or Hesco ($170)? The original pump seems to do ok in moderate climates, but it's been kind of dicy on hot GA days in my Jeeps. I've used the flowkooler on my 91 Cherokee and was happy with it, but have no experience with the Hesco one. Is it worth the extra money? I'm in Georgia and it gets retarded hot and humid here during the summer. I don't mind paying the extra money to do this right the first time, but if the Hesco doesn't actually cool any better I'd rather put the money towards other upgrades. 

 

 

Coyote

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The Hesco is a flowkooler with a huge markup as are most Hesco products. Unless you have significantly increased radiator capacity, stick with a stock flow pump. I’ve been down this road, the high flow thermostat housing is also a gimmick on a standard 4.0. You don’t want the coolant flowing so fast through the radiator that it fails to properly cool. The biggest difference is to get the thickest radiator core you can stuff in there. The Novak would be at the top of the list followed by maybe the mishimoto and cold case. Csf tends to have small cores. 
 

The stock system is fairly well balanced but If you radiator capacity is significantly higher than stock then a higher flow water pump works well. Also consider the GMB high flow pump. It doesn’t have a billet impeller but does flow higher than stick. Kind of falls in between the stock and flowkooler setup. 

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The fan shroud seems to be in good condition, but the mechanical clutch fan is suspect. When the engine is hot the fan can be turned by hand alot easier than I think it should. That's really neither here nor there, I was planning on replacing the mechanical fan with electric fans anyways. Not a fan of clutch fans, I prefer flex fans or electric fans. They seem to flow more air/cool better at low/no speeds....i.e. getting stuck in Atlanta traffic in July. Lol I didn't realize the flowkooler and Hesco water pumps were the same thing.... that's quite a mark up!!!

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Also in Georgia w/4.0. The absolute best thing I ever did was to replace the plastic recovery tank with an aluminum tank w/press cap. The stock pump works fine. Never had anymore over heating problems after I replaced that dumb plastic tank.

100_0578.jpg

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1 hour ago, olddude said:

Also in Georgia w/4.0. The absolute best thing I ever did was to replace the plastic recovery tank with an aluminum tank w/press cap. The stock pump works fine. Never had anymore over heating problems after I replaced that dumb plastic tank.

100_0578.jpg

That makes alot of sense. That pressurized plastic tank is a horrible design. 

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I don't think the HESSCO and the Flow Cooler are the same. It looked at pics, and the HESSCO has curved vanes, the Flow Cooler straight vanes with a discs on top. I think they used to pop rivet a disk on. Looks one piece. I do have a HESCO in the box. I do hear you need to put a restrictor in the upper hose to slow down the flow. 

       Also, another aspect as I see the OP has two with AW4 trans, is a trans cooler. Plenty of threads out there on this. 

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38 minutes ago, 75sv1 said:

I don't think the HESSCO and the Flow Cooler are the same. It looked at pics, and the HESSCO has curved vanes, the Flow Cooler straight vanes with a discs on top. I think they used to pop rivet a disk on. Looks one piece. I do have a HESCO in the box. I do hear you need to put a restrictor in the upper hose to slow down the flow. 

       Also, another aspect as I see the OP has two with AW4 trans, is a trans cooler. Plenty of threads out there on this. 

You're right, I do have an AW4 with the trans cooler built into the radiator. I'm sure that adds heat to the system and helps to contribute to the problem. The new radiator also has a trans cooler built in (supposed to be the same threads). Unfortunately the temp sensor hole for the electrical fan is threaded differently. It's difficult to get a temp sensor with the correct threads that will work with my existing system. The new radiator comes with 3 electric fans, 1 to replace the factory electric aux/a/c fan and 2 to replace the factory clutch fan. I was planning on just plugging that sensor hole in the radiator and using an inline temp housing (and correctly threaded sensor) to control all 3 electric fans (on separate relays). 

 

That seems weird that Hesco would sell a high flow water pump and then recommend using a restrictor plate to slow the flow. I've seen stranger things. Lol. My old flowkooler water pump was exactly like you described; sheet metal plate pop riveted to the impellers. It worked very well on my old 91 Cherokee for 12ish years before the Jeep finally died (unrelated to over heat/temp problems). I'm not sure if flow cooler still uses that design, will have to check and see.

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I just checked flowkoolers website and they did change the design. Instead of sheet metal pop riveted to the impeller, it uses a new machined aluminum impeller that looks suspiciously like the Hesco one. The Hesco very well may be a rebranded flowkooler water pump at twice the price. 

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1 hour ago, Coyote said:

I just checked flowkoolers website and they did change the design. Instead of sheet metal pop riveted to the impeller, it uses a new machined aluminum impeller that looks suspiciously like the Hesco one. The Hesco very well may be a rebranded flowkooler water pump at twice the price. 

I still doubt the HESCO and Flowkoolers are the same. From the pics I saw, Hesco has curved vanes. I don't think HESCO says anything about a restrictor. Hornbrod on this forum had the issue of to fast of coolant flow.

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1 hour ago, 75sv1 said:

I still doubt the HESCO and Flowkoolers are the same. From the pics I saw, Hesco has curved vanes. I don't think HESCO says anything about a restrictor. Hornbrod on this forum had the issue of to fast of coolant flow.


They are the same. I’ve ordered both. The flowkooler does not have a stamped steel plate spot welded to the impeller. It has a billet unit. Hesco has been rebranding these things for years along with a LOT of other parts. They made huge markups selling “custom” parts that were really just of the shelf items that they found out fit the 4.0. Their valvetrain products, electronics, sensors, water pumps etc are mostly just rebranded parts. They’ve been doing this at least since 2012. I should make a list of all the stuff I’ve bought from them that was “custom”. Here are a few examples: “Hesco” high volume oil pump: Melling part number on box. “Hesco” timing chain: Cloyes part number. “Hesco” vss to run a cable speedo and have an electric signal for the ecu: standard parts 91 YJ VSS (huge markup here). “Hesco” high volume water pump: flowkooler. 
 

Not saying they don’t machine any parts anymore but very few it would seem. The high flow thermostat housing is just an off the shelf crown unit with a 1” sanding drum run over the choke point at a 45*. Nothing “custom machined” about it.  

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388A783B-F555-409F-96C1-5F6FF8AC7206.jpeg.94757e072fbb377bbd9e8085ff3cded7.jpeg
 

$149 at Hesco. This is an airtex e2000 pump. $55 all day long. and you have to ask yourself: when did Hesco get the factory to start manufacturing fuel pumps?

 

B8EFB3D8-783B-4E80-9C8F-B2DD8A18A3CF.jpeg.7ce1582467bf5918eb1fb7175fd45be6.jpeg

 

$122 at Hesco. $44.79 on rock auto. 
 

They’ve been doing this for years and they thrive off of unsuspecting Jeepers. 
 

Apologies to the OP... I’m done now :peep:

 

 

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5 hours ago, 75sv1 said:

I'd probably recommend a MOPAR water pump. I think someone on this site sells them. 


I haven’t seen anyone on here sell them but I did say at some point that Chrysler still makes the water pump for the 4.0L. I have two reman 2.5L pumps. 

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4 minutes ago, eaglescout526 said:


I haven’t seen anyone on here sell them but I did say at some point that Chrysler still makes the water pump for the 4.0L. I have two reman 2.5L pumps. 


Ive been curious about that also. Haven’t seen a new Mopar unit but probably worth a shot. Is the 4.0 part number still available new from Mopar? 

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That GMB high flow actually cooled better than anything I’d used before and I ran it for about 5 years with zero issues. The flowkooler just moved water too fast for a stock radiator setup. 

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16 minutes ago, ghetdjc320 said:


Ive been curious about that also. Haven’t seen a new Mopar unit but probably worth a shot. Is the 4.0 part number still available new from Mopar? 


Yup! It’s a newer number but still made to this day. 

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I just bought a new Mopar water pump for my 91 - has the Chrysler pentastar cast into it and everything. Comes with a beaded gasket just like the Mopar thermostat packages have as well.

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  • 2 weeks later...

Installed the flowkooler water pump on my 1988 RENIX 4.0. Everything was straight forward, just like installing a factory water pump. After 30 mins of running I had a slight leak at the bottom driver's side corner. Retorqued the mounting bolts and everything was good. A word of caution; this pump does flow more than a factory unit and will create higher pressures in your cooling system. That's good for getting out air pockets and general cooling, but not good if you have old hoses, bad connections or a weak radiator/heater core. I replaced all of the hoses just as a precaution/general maintenance and was installing a new radiator at the same time anyways. I've only had it operational for a few days, but I've been running it pretty hard doing 0 to 60 tests. It holds rock solid temps whether I'm running it hard or idling in the drive thru. I'm not sure if the improvement was due to the flowkooler pump, new radiator and hoses or the electric fans, but either way I'm impressed and ready for the scorching Georgia summer.

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A 4.0 cooling system will do an "acceptable" job of keeping the engine at normal (design) operating temperature, even with air conditioning, and even in extreme temperatures.  I live in Phoenix, and have had three XJ's and MJ's that have successfully operated in a climate where daytime temperatures regularly go over 110*, and pavement temperatures are regularly above 140*.

 

The key to a successful cooling system is one where ALL the OEM components are operating as designed, and therein lies the trick:   many owners neglect little things like a worn viscous clutch fan, or a missing mechancial fan shroud, or a slightly degraded radiator.

 

I have found the the following combination of OEM parts to be quite effective

 

1.  regular water pump (and major brand is just fine, and there is no need to spend money on something fancy)

2. a fully functional viscous clutch

3. a proper fan shround

4. the electric cooling fan that was found on later model XJ's

5. a new EIGHTEEN pound pressure cap (on an open system) 

6. a quality 195* thermostat

 

I do deviate in one way from OEM parts---I run a CSF all-metal 3 row radiator.   I cannot say if it works any BETTER than an OEM, but at least the plastic tanks won't degrade in our intense heat here.

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1 hour ago, AZJeff said:

A 4.0 cooling system will do an "acceptable" job of keeping the engine at normal (design) operating temperature, even with air conditioning, and even in extreme temperatures.  I live in Phoenix, and have had three XJ's and MJ's that have successfully operated in a climate where daytime temperatures regularly go over 110*, and pavement temperatures are regularly above 140*.

 

The key to a successful cooling system is one where ALL the OEM components are operating as designed, and therein lies the trick:   many owners neglect little things like a worn viscous clutch fan, or a missing mechancial fan shroud, or a slightly degraded radiator.

 

I have found the the following combination of OEM parts to be quite effective

 

1.  regular water pump (and major brand is just fine, and there is no need to spend money on something fancy)

2. a fully functional viscous clutch

3. a proper fan shround

4. the electric cooling fan that was found on later model XJ's

5. a new EIGHTEEN pound pressure cap (on an open system) 

6. a quality 195* thermostat

 

I do deviate in one way from OEM parts---I run a CSF all-metal 3 row radiator.   I cannot say if it works any BETTER than an OEM, but at least the plastic tanks won't degrade in our intense heat here.

I think you hit the nail on the head. The key is to make sure EVERYTHING is operating correctly. I've had 4 clutch fans go out on me over the years (2 different XJs, a TJ and MJ). It's not like the fan just dies over night, it's very invidious. You notice temps start creeping up till one day you realize that you seem to be over heating an awful lot lately. 

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3 hours ago, AZJeff said:

A 4.0 cooling system will do an "acceptable" job of keeping the engine at normal (design) operating temperature, even with air conditioning, and even in extreme temperatures.  I live in Phoenix, and have had three XJ's and MJ's that have successfully operated in a climate where daytime temperatures regularly go over 110*, and pavement temperatures are regularly above 140*.

 

The key to a successful cooling system is one where ALL the OEM components are operating as designed, and therein lies the trick:   many owners neglect little things like a worn viscous clutch fan, or a missing mechancial fan shroud, or a slightly degraded radiator.

 

I have found the the following combination of OEM parts to be quite effective

 

1.  regular water pump (and major brand is just fine, and there is no need to spend money on something fancy)

2. a fully functional viscous clutch

3. a proper fan shround

4. the electric cooling fan that was found on later model XJ's

5. a new EIGHTEEN pound pressure cap (on an open system) 

6. a quality 195* thermostat

 

I do deviate in one way from OEM parts---I run a CSF all-metal 3 row radiator.   I cannot say if it works any BETTER than an OEM, but at least the plastic tanks won't degrade in our intense heat here.

:yeahthat: Mopar pump and t-stat IMHO 

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