[LPete]

This is interesting -- this is from the patent on the device (Unified Patents - Analytics Portal). It doesn't talk about pressure, but it talks about a high flow rate causing heater core erosion and damage.

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In many if not most vehicles, the coolant is circulated by an engine driven pump. Since the engine speed varies during vehicle operation, the flow rate of coolant in the heater circuit changes as well. Because the heat output of a heat exchanger is determined primarily by the temperature and flow rate of coolant through the exchanger, the heat output of the heater core also varies with engine speed. The output of the heater with the engine idling and the vehicle at a standstill is substantially less than the output of the heater with the engine turning at a substantially higher RPM, i.e., when the vehicle is traveling at highway speeds.

It has also been found that the useful life of the heater core is substantially reduced if high coolant flow rates are allowed to proceed through the heater. The reason that the useful life is diminished at high flow rates is due to particles and other matter which are carried by the coolant. This matter may comprise normal residue left in the engine block coolant passages from the manufacturing process including sand left from the casting process and metal shavings left from the machining processes. These particles and other matter act as abrasives and abrade the inside of the passages in the heater core which are usually constructed of rather thin materials in order to promote heat exchange. At high fluid flow rates, this normal abrasion process can be greatly accelerated thus reducing the life of the heater.

As indicated above, high flow rates normally occur when the engine is turning at high RPM since the water pump is mechanically coupled to the engine. For this reason, many vehicle manufacturers place restrictions in the coolant lines feeding the heater to prevent or inhibit high fluid flow rates through the heater passages.
In the past, these restrictors operated satisfactorily to reduce the maximum flow rate of fluid through the heater at high engine speeds. However, these restrictors also restricted the flow at engine idle speeds. It has been found that in modern-day automobiles the amount of heat available in the coolant for heating the passenger compartment has been reduced. This reduction in heat availability is a result of using the coolant for other functions such as cooling turbochargers and other auxiliary equipment now forming part of modern automobiles. As a result, in vehicles that employ restricted coolant lines, insufficient heat is available for the heater when the engine is idling and unsatisfactory passenger compartment heating occurs on extremely cold days.

 

[Road Ripper]

That makes sense, especially since our vans don't use a water valve anymore to limit flow/heat - it circulates all the time. The abrasives in the coolant would act like a water jet over time.

 

[Patrick_M]

Just had this fail today on my 2006 3.8L. The valve had become brittle and cracked at the base of the inlet. As a quick fix, I installed a Koehler 5/8in Heater Hose Connector Kit Part # H58 I picked up locally. Waiting for the OEM replacement 4677378AB from moparonlineparts.com to arrive. I did replace all of the OEM hose clamps with the screw type. I've never had good luck reusing OEM clamps.

 

[Patrick_M]

Well, not sure if a fragment off of the restrictor valve was still in the system or just sheer dumb luck, but the water pump failed this morning and started leaking out of the weep hole. Got that replaced, wasn't too tough. Went ahead and replaced the alternator while I had everything apart since it has been groaning for a long time.

 

[imjokerbatman1978]

I'll probably need to see if I can find the old valves I have laying around to give a definitive answer. In a condensed version of my saga regarding replacing this valve long ago, I know that I figured out that the Dorman valve I purchased was configured backwards from the OEM and other manufacturer's replacement valves I went through on my adventure. Basically, there is a rubber grommet/oriface/seat inside the body of this valve with a spring holding it "closed" against one side of the valve body. Presumably, the coolant flow direction should act to compress the spring to increase flow around this grommet as pressure increases and the grommet/seal is pused back away from the valve body wall. IIRC, I used a pencil (eraser end) to play around with each valve and prove to myself that the Dorman valve was configured with the spring and valve seat (grommet thing) reversed as regards the arrow direction compared to every other valve I had. Though I like the "fused body" design of the Dorman, this shook my confidence enough that I ended up going with another manufacturer's part instead. If your Dorman valve is also designed "backwards" then it should go in the opposite direction of the OEM valve; however, I'd be concerned that they might have corrected the issue since then? IIRC, the OEM valve had the arrow installed pointing toward the firewall and the spring compressed in that same direction; however, I need to re-verify this. Would suggest seeing which way your Dorman valve compresses any maybe we can figure it out from there... This is unlikely to be the reason your van is over-heating... as I understand it, this valve purely serves to assist with getting heat to the rear of the van when the coolant flow/pressure is low...

Sir the valve was created as a recall to cure an over heating issue as well as a gurgling sound from the house that's verbatim from the dodge dealership so if installed backwards will definitely cause over heating

 

[FabricGATOR]

Sir the valve was created as a recall to cure an over heating issue as well as a gurgling sound from the house that's verbatim from the dodge dealership so if installed backwards will definitely cause over heating

Welcome to the forum

Your very first post and you are submitting useful information. We love members like you.
We look forward to reading more from you,
Cheers!

 

[Jeepman]

Just a flow control valve of sorts, the system will operate without it, later years didn't have it. Something to do with rear heat. GM and others use it too.

These type of restrictors are used for different reasons.
1) to cut down the coolant flow to keep the core from getting worn out by erosion. This is normally done on vehicles with large cooling systems with large pumps IE trucks.
2) to cut down on the noise of coolant rushing through the core.
3) to cut down on the flow to the front core so the rear core will get enough flow (balancing as was mentioned in an earlier post) if you have a rear heater.
Leaving your's out is unlikely going to cause you any trouble IMO.

The "rocket science":
"Patent # 4800925
A two-stage flow controller for use in a vehicle heating circuit including a housing defining an inlet and an outlet and a flow control chamber disposed between the inlet and outlet. A spring biased flow controller is disposed for sliding movement within the chamber towards and away from a valve seat. The flow controller includes an annular segment defining a through aperture and a plurality of axially extending legs which support the segment for sliding movement within the chamber and in predetermined alignment with the valve seat. Projections are defined on a face of the annular segment. When the fluid flow exceeds a predetermined level, the projections initially engage a valve seat surface such that a variable orifice is formed by clearance regions between a confronting face of the element and the seat. The element deforms to diminish the clearance space between the face and the seat as a function of fluid flow rate. In a preferred embodiment, the housing includes two portions that are snapped together and are maintained in their assembled positions by a resilient retaining ring. Locking lugs are supported beyond an end surface of one of the portions by a plurality of arcuate tabs which together define a segmented groove having a diameter larger than an end bore defined by the portion. The other portion is sized to fit within the end bore and includes a groove for receiving the retaining ring when compressed. When the second portion is inserted into the bore, the retaining ring expands outwardly into the segmented groove to maintain the engagement between the two portions."

References:

Mystery Part in Heating System - What to Do?

Today my better half was driving the DGC (204K miles)and called to tell me that there was steam coming from the hood. She said it wasn't overheating so I asked her to get it home. The coolant was a bit low and I have a pressure tester so I put about 16 PSI in the system. Sure enough, it was...

www.chryslerminivan.net

Variable Restrictor Valve Flow Direction?

I purchased a Dorman - OE Solutions - Variable Restrictor Valve (Part No. 902-008). There is an arrow on the part that is suppose to face firewall. There is controversy on which direction the valve is suppose to face. Many people are reporting the the arrow is incorrect. I no longer have my OEM...

www.chryslerminivan.net

 

[ScuzziOne]

Sir the valve was created as a recall to cure an over heating issue as well as a gurgling sound from the house that's verbatim from the dodge dealership so if installed backwards will definitely cause over heating

Got a TSB number? Would like to see that one...