My engine is now out, and before I put it back, and make getting to the most rearward threaded plugs almost impossible, I'd like to track down any mods to keep the back cylinders a bit cooler.

Any links to articles or diagrams would be most appreciated!

Thanks,
Bob
Waxahachie, TX

 

Since the restriction is inside the block not sure you can make a material difference in the coolant flow on those cylinders without impacting something else.

If you start pulling flow out of the back of the block what happens to the return flow to the water pump? You cut it down it leaves the possibility of that portion getting warmer than it should.

Where exactly is the restriction that supposedly causes flow issues? On the coolant feed or coolant return flow? Can the plumbing be done so it does not interfere with the current flow to the point it actually helps?

Pressure relief is obvious for the back cylinders, but, when and how much would you return for cooling relief is another whole question that hasn't really been explored.

Good luck anyway as its a interesting subject.

 

It's been a known issue for quite some time. Here's the details of the freeze plug kit:

1x 3925226 Connection/Water Transfer
1x 3910530 O Ring
1x 3910677 Coupling, Hose Elbow
1x 3008468 Pipe Plug
2x 3910495 Hex Flange Head Cap Screw

This is the Cummins part#s/kit for what basically amounts to an unregulated 5/8 water line straight out of the block. I haven't inspected the blocks to be sure, but maybe the later 24v blocks don't have a freeze plug in a good spot, or maybe they are different sizes, or whatever. The 12V/early 24v kit described uses a freeze plug on the back (actual back, not side) of the block. The later engines use a half inch NPT port out the rear of the head. Get the kit here, if you've got the engine out and it's a 12v/early 24v:

94-02 Dodge 5.9L Cummins Cooling Kit Improves Coolant Flow to Cylinder #6

It's not really a restriction, more of a design deficiency or the inherint limits of block design that many engines are subject to. The Cummins inline 6 is just more vulnerable to it than most. They get worked very hard in many applications, and of course race tracks and sled pulling tends to generate a little more than normal heat and rpm.

The wheel has even been reinvented for those of the latter pesuasion to address this issue in the form of colorful anodized fittings, regulators and steel braided hose.

 

only thing i can think of is a "cooler" thermostat

 

Not a good idea. The engine needs to run at a certain temperature to operate efficiently. The problem is, regardless of what that temperature is regulated to, the rear of the block runs hotter. It's just the nature of the beast. Only way to affect it is to get more water flowing back there.

 

I understand the inherent restriction in the design and operation of the 12/24V blocks but not sure if it was still an issue in the CR blocks. Do they list a kit for the CR's or does it just supposedly work the same?

 

Same deal, they just take it out a port on back of the head. I heard there is a Cummins kit but never ran across it or saw the details because it's so easy to just tap into the head yourself.

 

I installed an OPIE BYPASS specifically for the issue you are trying to address. Check the vendors section here, also other websites that have good information regarding the Opie bypass. It is a pressure regulated bypass. comp diesel site has quite a writeup in their vendors section - intelligent engineering IS opie.

Hope that helps.


NP

 

I have a theory on this, let me know what you think. I've been looking at the Evans NPG waterless coolant. Since it has a boiling point of over 400* it doesn't build pressure to make hot spots in the engine. My theory is, since coolant builds pressure and makes vapors in the system and we have a "dead end" back by the 5 and 6 cylinders that all the vapors build up in that area and will not allow the liquid coolant to get back there like it should. That is why the Opie system will work, when the vapor pressure builds up the pressure relief valve will open and release the built up pressure to let the liquid coolant flow back there. IF this is the case then changing the coolant to the Evans Coolant should help with this problem. I've never tried the Evans coolant, just read about it and it seems like it would work. Let me know your opinions.

Doug

 

I doubt it will help much because it addresss the symptom, not the root cause. Where does the heat go? You need more coolant flowing, with "flowing" being the key concept here. Increased flow results in more cooling. Whether or not vaporizing the coolant comes into play is variable, depending on workload. If you are vaporizing internally it is already way past the safe margin. I believe the pressure issues is more rpm-induced than a heat/vaporization issue.