Coolant bypass question - Dodge Cummins Diesel Forum
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post #1 of 11 (permalink) Old 11-15-2019, 12:23 AM Thread Starter
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Coolant bypass question

Hey all, if I am plumbing in a rear freezeplug cooling bypass, do I need the small bypass hose that goes from the head side of the t stat to the upper coolant neck? I was thinking of plumbing my bypass into this threaded fitting on the coolant neck to avoid adding another T in somewhere. It will be run on a pressure relief valve on its lowest setting, approx 30-50 psi

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post #2 of 11 (permalink) Old 11-15-2019, 12:59 AM
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I thought of that but decided it was to small. So I made a 'T' for the top radiator hose. Was easier than working with the other small hose. Will try to post a pic here.
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post #3 of 11 (permalink) Old 11-15-2019, 07:14 PM
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That small hose isn't a bypass. It is a route to expel air from the engine cooling system when the engine isn't running. The engine side is a one way valve that the hose is connected to. It is called a jiggle valve.

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post #4 of 11 (permalink) Old 11-16-2019, 10:20 AM
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One could plumb the rear freeze plug outlet to the heater core inlet, gets the stagnant coolant around #5 & #6 moving.

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post #5 of 11 (permalink) Old 11-16-2019, 10:43 AM
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In concept it works but in reality those PRV do not lower your water pressure, because they don't bleed enough pressure off fast enough. I had mine set to 25 psi and was still seeing over 50 psi @ only 2000 to 2400 rpms. The way I fixed mine was to remove the thermostat, and put a PWM on the water pump. Now it never goes over 20 psi.

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post #6 of 11 (permalink) Old 11-16-2019, 11:57 AM
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Gator1 at the risk of seeming obtuse what does 'PWM' stand for and how did you monitor the pressure in the coolant sys?
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post #7 of 11 (permalink) Old 11-16-2019, 12:04 PM
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Quote:
Originally Posted by 63willys View Post
Gator1 at the risk of seeming obtuse what does 'PWM' stand for and how did you monitor the pressure in the coolant sys?
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I spent over $300.00 for a gauge that monitored pressure with a gauge that read in real time and with a memory so that if there were pressure "spikes" that you wouldn't notice unless you had memory recall to tell you the maximum pressure reached. I got very tired of all the claims from shade tree mechanics, and manufacturers selling devices to cure the problem. I wanted to know without a doubt what was going on inside, and proved it's all BS.

PWM stands for Pulse Width Modulator...

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post #8 of 11 (permalink) Old 11-16-2019, 03:03 PM Thread Starter
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Quote:
Originally Posted by GAmes View Post
That small hose isn't a bypass. It is a route to expel air from the engine cooling system when the engine isn't running. The engine side is a one way valve that the hose is connected to. It is called a jiggle valve.
great info, thanks for that.
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Originally Posted by ofelas View Post
One could plumb the rear freeze plug outlet to the heater core inlet, gets the stagnant coolant around #5 & #6 moving.
think this is the route i am going to go. What gator had mentioned about the PRV not bleeding fast enough makes sense, but I would venture to say it would still help as a plug may be able to hold higher pressure instantaneously than over time. Id rather have the full time bypass that running it through the heater core would provide.
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post #9 of 11 (permalink) Old 11-16-2019, 05:15 PM
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You're better off either cutting or grinding down the blades on your pump, or just run a line from the back of the block to the rad so it can keep up. The PRV is not doing anything measurable at all....Maybe if it were set @ 5 to 10 psi it would actually help, but the passages in the head are too small to let the coolant flow enough also. I've already proven that beyond any doubt.

The factory tech manual says it should never exceed 20 psi and it does that below 2000 rpms.

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post #10 of 11 (permalink) Old 12-02-2019, 05:12 PM
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i'm a self appointed newbie here and have been reading up on these bypass threads...but still have questions...

are thermostats and pressure regulators needed to flow the coolant from 5/6 back to the water pump?

i guess what i'm asking is if something like this be used without a thermostat like Fleece or a pressure regulator? https://puredieselpower.com/dodge-pr...ylinder-6.html

or...could someone just "T" off of the temp sender at the back of the head back to the water pump?

I guess without a thermostat at the back of the head for these bypass systems, heating up to operating temp could take longer...?

thanks.

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post #11 of 11 (permalink) Old 12-02-2019, 05:19 PM
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I'm not fan of these "bypass kits with PRVs" on a 12v.

A complex solution to a simple issue.

R12.5z in the summer, Webasto in the winter; cassette tapes & CES-20078.5z all year.
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