Installing valve in water line from head to heater core

I’m not understanding the hate going on for someone to mod their truck. There have been lots of needless and crazy mods described on this forum over the years, but few I’ve seen so much strong disagreement from some of my most highly respected friends.

We’re talking about a simple cooling system mod, not about deleting emissions equipment. I’m specifically referring to my 12-valve, since I’m unfamiliar with the 3rd and 4th Gen systems. The use of a valve like I posted would not shut off any coolant flow except to the heater core. If you’re concerned with coolant stagnating in the core, open the valve up every once in a while and let it flooowwwwww….. If you’re concerned with leaks from numerous connections, how can you stand to drive a 4th Gen with all the y-pipes and, correct me if I’m wrong, even two radiators on some diesel pickups now?

 

3rd gens are known to have a hot 5/6. The heater core flow comes from those cylinders, so if you block it off (or slow it down) you reduce flow to the rear of the block. At higher power and rpms that creates a potential issue that many have experienced.

This is why there are all kinds of mods to increase flow to the rear of the block and to reinforce the freeze plug.

So it’s not a hatred of a mod, but rather a recommendation to not complete a mod that reduces flow to 5/6 where there is a known concern.

 

Heat is one thing. Humidity another. Control the latter and the former responds to cooling quicker and more effectively.

I run a large de-humidifier year-round in my travel trailer. Use of A/C or furnace heat is lowered (offset by dehumidifier AC draw).

Being able to use the heater core to some extent is the trick for vehicles. It’s not easy to get right. Living at altitude out west with its low humidity isn’t a representative situation (population too low). Living in the desert not much more so. Places where it cools off at night aren’t anything like the US Gulf Coast or Texas where humidity can be high, and temps barely subside overnight.

Mods to find satisfaction are fully justified. Vehicles get old. Weatherstripping ages. Etc.

An A/C system in the tough areas has done what it can over about 6-7/years. Then it’s time for R&R.

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The valve I posted would not restrict flow to anything but the heater core.

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Redpatcher0481:
"The only thing I would do is open that valve 2-3 times a month and let fresh coolant into the heater core. I would suspect letting that old coolant sit in the core for months would start to become corrosive and cause the core to fail come winter time. Like it used to do on the older cars."

If I added a bypass, I would do the same thing. But since I get 40* vent air when the refrigerant is at level I don't think it would be good to drop it another 10-15 degrees. I can't imagine 25*-30* vent temps being good. Even in the summer, a lot of times when I am driving for a long time I increase the temp some once the cab is as cool as I want it. Vent temps then are around 50*. One thing for sure though, is that this thread reminds me of how much I miss the old school AC systems, and how well they worked, even on the hottest days when you were stopped at a stoplight under the blazing sun. I mean I really miss them!

Agreed. That's why I am comfortable adding a can of 134A every other year instead of spending thousands to get the AC fixed like it should be. If I had to I could do it every year and never get close to what it would cost for a proper repair. Either I would die, or the truck would die before I spent that much.

 

Simple cut and splice. Zero issues, so far.

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All of the valves I linked to above have the same flow pattern as shown for the valve BigPapa posted. What that means is all of these valves (4-port valves) maintain full flow from the head to the steel pipe regardless of the position of the valve. The coolant either all goes through the heater core and then into the steel pipe (bypass closed, winter mode), or all returns to the steel pipe, "bypassing" the the heater core (bypass open, summer mode), but STILL flowing. That's why they're called "heater core bypass valves" rather than "heater core shut-off valves" like Rowdy Dalton's setup. There is nothing to worry about regarding cylinders 5 & 6 with any of these 4-port bypass valves.

Yes, some older Chrysler/Plymouth/Dodge vehicles did employ a non-bypassing shut-off valve to improve A/C performance by also keeping hot coolant from flowing through the heater core depending on the motor that was installed, but those were not 4-port valves.

The Mopar system I discussed above works the same too. According to my research the vehicles that had these from the factory were set up so that they would fully bypass the heater core only when the air conditioning control was set to MAX.

It's just a knee-jerk "hatred" reaction going on, not understanding the flow of the 4-port bypass valve.

 

No, there is more than just 4 port valves being discussed…

 

I got involved in one of these debates years ago and vowed never again…because nobody listened..but here I am..

So here is a brand new Freightliner M2 on our lot that just rolled in from the upfitter..

Notice engine make and nomenclature….and the dreaded valve…from the FACTORY!

Neither DTNA or Cummins would allow this if it caused any problems…they have done this for decades!! I can pop the hood on just about any Class 6 - 8 truck in this yard regardless of engine or truck make and there will be a set of shut offs for the heater core. This oil truck will see a lot harder duty cycle than most Rams..

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The harder duty cycles also usually are accompanied by lower power ratings, but yes they get worked hard.

 

All the school buses have the ball valve as seen above.

 

What’s their hp rating? What’s their redline? AFIK the rear heat/freeze plug issue is more common in the Dodge application.

The only 5.9 I know of with more hp and rpms than the HO in the Dodge is the QSB, which also runs a cooler thermostat so there is is likely much less on an issue on 5/6.

 

Shiny!

I notice that those valves on the Freightliner are manual. What does the operating manual say about when to close them? Are they there strictly for isolation, diagnosis and repair; or are they ever intended to be closed during steady-state normal use?

Also, do those trucks and school buses have the same style exhaust manifold as the 3rd generation Dodge with the 4 rear cylinders all bunched together, or do they use a design that allows cylinders 5 & 6 to breath more easily?

 

Don't confuse hatred with valid concern. Some people have concern about adequate cooling for cylinders 5 and 6. I have concerns about stagnant fluid in the heater core. A true bypass can alleviate the temperature question, and opening the valve periodically in the summer can alleviate the stagnant water question. There is no hatred involved. I've never had the impression that anyone here has had anything other than everyone else's best interests at heart. I neither gain or lose anything when anyone else does any modification to their truck (with the exception of if I am riding in it and their modification caused an accident that injured or killed me). I think the same is true for everyone else who has posted their opinion over the years. The reader's job is to look at all sides, and reconcile any modification with the purpose of their truck and risk/benefit that derives from said modification. It's not complicated.

 

What do you mean by rear 4 bunched together?

 

Way, way back before A/C was common in big trucks and heat from direct drive engine fans would literally roast a driver in the summer we used these valves to shut the water off to the heater core in hopes to drop the in cab temps just a bit…and also were very handy if the heater core was starting to leak and starting fogging the windshield…

The valves are now used to assist the A/C discharge temps in the summer and just like then will allow operation of the truck in the event of a blown heater core.
Truck cabs are better sealed and insulated than back in the day but shutting the water off to the heater core still makes a noticeable difference in summer time driving comfort.

 

I can’t remember the manifold configuration, I think the turbo is towards the front…I will look in the morning..

 

The bus engines are rated at 230-250 if I remember correctly. I dont know what max rpm is. The coolant on the buses is routed to a driver’s heater, a front or step-well heater, then at least two rear under-seat or rear wall heaters. The longer 84-passenger buses have close to 50’ of 1” heater hose. All the buses have a booster pump to pump the coolant to the rear heaters. I’ll have to compare the exhaust manifolds tomorrow if I can remember.

The valves are closed when heat is no longer needed and opened back up when it cools off. Most buses don’t have A/C. The front heaters have an electric or cable operated shut-off valve at the cores, also.

 

Sorry fellows. I was off Friday and Monday, wife had foot surgery, and I had a hectic and busy day today. Didn’t get a chance to look at the exhaust manifolds.

 

I have not fallen asleep at the wheel either, just not much free time so far this week.

I did begin a study of the coolant flow piping using my 2020 as the test case. Turbo and EGR cooler lines will not be affected by shutting off the heater line that comes from the cylinder head.

I will attach graphics when I get a few minutes.stay tuned..