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7/9 Updated Heater Control Valve

Well mine broke in half. I can assume its ok that I bypass this valve completely in my 97 V90 if I don't plan to use my air conditioning? But will the heat be strong enough for the winter?
 
With the valve bypassed completely then you will have full flow thru the core, so yeah, you should be nice and toasty. I'm not sure if the V90 uses the 7/9 style heater setup or the 850 style. The 850's run a constant flow core using just a blend door for temp control.

Your GM valve broke? Any chance of pic's? We're getting to be a few years into this mod so I'm curious to see what the failures are on these. I've had to replace mine after it started seeping from the shaft, otherwise no issues.
 
I'm trying to sort out the various options for this part. From what I'm finding, there seem to be two different models, one labeled as "bypass" and one as "non-bypass."

The one that I think you all are using is:

NAPA 6601357
Murray 74607 (O'Reilly)
Everco 74607 (Autozone)
Four Seasons 74607 (Amazon)

These all seem to be the same part (and all made by Four Seasons). They all say something along the lines of "Vacuum Closes Heater Valve" and "Non-Bypass."

The other option, and the one I'm thinking of using, is:

AC Delco 15-5543 (Amazon)

Or on Ebay for $27

"GM Original Equipment Heater Bypass Valve"

This one says "When the heater valve is closed, the bypass valve diverts the coolant flow back to the engine. The valve maintains coolant flow through the thermostat housing to ensure correct operation of the thermostat."

Am I missing something? Are these labeled wrong, or are some of these bypass valves and some of them not? Are you installing the non-bypass ones backwards to make them work, or are these all exactly the same?
 
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Incorrectly labelled on the non-bypass units. By design they either allow coolant to the core, or to bypass the core. The stock valve is a non-bypass, that either allows coolant to flow thru the core, or not flow at all.
 
Got a month out of my most recent scantech HCV. Off to the parts store

Update with my thoughts from the job: Getting the hoses on there kinda sucks. Bring some silicone lubricant to help things along. How do hose clamps disappear? Get 4 new hose clamps, trust me. And you're probably best off getting new hoses on at the same time. Rubber, not silicone. Looking forward to 5+ years of not changing the damn thing though!
 
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Which hose is which on this?

My inlet hose almost turns back on itself and the outlet isn't much better.

thelostartof said:
Bump

rps20130314_203819_614.jpg


Just installed this, works great so far, install was a PITA because of my giant intake manifold, a nathan intake would make life so much easier.

Everyone should do this on their 7/9, I shall update the 944 with this in the coming months
Click to expand...
 
Look at your existing plumbing before you remove it. The top pair on the new valve go into the bottom port of the heater core, bottom pair go into the top port of the heater core.
 
On the one hand, I believe there is also a "bypass" passage for the thermostat, which closes when the thermostat opens. I'm surprised that this is even an issue. The pump is set up to feed water from inside the head to the lower rad hose, and to ultimately pull that water back through the upper rad hose, head, and block, and optionally heater core. Maybe that one passageway that is/n't tapped if the valve is closed makes the difference, but I'm skeptical.

When you were checking head temps, was the original design valve new or old and crappy? Was the heat on? If the only difference in temps is from coolant flowing, then disconnecting the vac line to the heater valve should open the valve and give you the same drop in temps in the back of the head.

On another note... I'm never putting a plastic control valve in my volvo. There's an ACDELCO all-metal version. The OE design was all-metal. This plastic business is to reduce manufacturing costs... and maybe help accelerate the death of older cars to sell more new ones.
 
The temps measured at the head were taken with a fresh replacement OE style valve that I did confirm had a full range of movement before install. Temps with the valve closed and open were taken. With the OE valve closed, as used in normal operation were approx. 20-30* higher than with the GM valve installed, with the valve in it's normally closed position as well.

At the time I was looking for a replacement, I did see the metal version but had no specs on it, plus the one place I was able to find info on it was unable to attain one, their supply chain was out of stock.

When mine is due for replacement the next time, I'll see if I can find the metal one, assuming the inlet/outlet pipes are indeed the same size.
 
The concept makes perfect sense. The outlet from the head (with the stock valve) gets blocked off when the AC is on MAX. If the coolant can't flow, it gets hotter there (likely on the hottest days)

With this GM valve, the coolant is allowed to continue on it's way back to the water pump (and oil cooler if it's a coolant style) and just ignore the heater.

That said, I'd prefer an all metal one. But I wouldn't know how to even look it up.
 
Actually it's not even just with the AC on max. Any time the temp slider is on the full cold position, the heater valve is closed. Once you crack it open just a hair, it opens the valve. I usually leave mine cracked just a little just so the core does a little cooling, except on the hot days.

I'll have to look for a metal one at some point...
 
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