7xx 9xx heater control valve

[h20ham]

Purchased a FourSeasons 74603
other than i will install at a elbow in hose (rather than the straight section)
these are all metal, and $20. Not mixed plastic metal $60

comments please

 

[hessam69]

I prefer the straight OEM type (not 90° angled like your example)

Easier to keep the hoses straight

 

[h20ham]

Ah, I would too. But, they are pricy, and plastic. Sure that is a overpriced piece of junk here in Canada anyway… maybe down-under they are quality?

think there are enough bends to make it work, but. Maybe there is a better option?

 

[PCH]

I've seen people use this GM one for like $14 on 7/9's

 

[bgpzfm142]

I've seen people use this GM one for like $14 on 7/9's

But that type only interrupts the coolant flow to the heater core. In a 7/9, the heater core is permanently in the cooling circuit until one presses the recirculation switch, and then vacuum operates the tap. Cabin temp regulation is done in 7/9s by flaps in the HVAC, not by regulating the coolant flow to the heater core.

You wouldn't want to engage "recirculation" in hot weather with that type of tap. It cuts off the coolant flow between the water pump pipe and the back of the head.

Which is why my grandpamobiles all use heater taps that do this, because OZ has always had stupid high summer temps, like many USA folks are getting now.

This type of tap also has the advantage that when the heater core craps out and starts leaking, you can just jam the tap on so coolant bypasses the heater core, then you can top up the coolant and it will get you home.

 

[Fa182]

In a 7/9, the heater core is permanently in the cooling circuit until one presses the recirculation switch, and then vacuum operates the tap. Cabin temp regulation is done in 7/9s by flaps in the HVAC, not by regulating the coolant flow to the heater core.

I know this doesn't apply to OP, but want to have it noted in case someone reads through this.
In 7/9 with manual heater controls and without AC, this is not true.

For example my late 1997 940 does not have AC and just standard cable-controlled heater controls (yes, AC was not standard equipment in EU in a 940 even until the end of their life in 1998).

If you turn the temp knob all the way to "cold", the heater valve completely shuts closed and therefore cuts the circulation through the heater core.

I had the old valve explode on me and hot coolant all over my feet in my 940 on a hot summer day once, when I revved the engine quite high on a windy mountain road.


Those cars use this control unit and valve:

 

[DET17]

This might not help the fellow in Austria, but in the States we have (had?) access to the GM valve to replace the failing OE parts.

I documented this change (but didn't discover it) in my "Cheap Thrills" build thread. That valve worked well.

Indeed as noted above, the circuit is slightly different in the 7/9 machines. From memory, usage of the proper valve allows the coolant from the back of the redblock head to flow back to the suction side of the vasserpumpen whether the heater circuit is engaged or not.

All from memory, on little coffee thus far this morn! It has been a long time since I visited Vienna, I will never forget St. Stephensdome..... nothing like that will ever be built again by humans.

 

[white855T]

The common replacement is the ford motorcraft heater valve. Used on tons of 7/9 cars with no issue. Yg-136. Seems its not easy to find anymore.

 

[h20ham]

All good stuff Ive forgotten over the last 30 years. So thanks.
also things have changed in the parts world. More since cv19,20,21,22,23…
Thanks white855t, Yg-136 Is the same it seems though as the plastic/metal 4seasons I opened with.

now to find a all metal unit like bgpzfm142 suggest, though I suspect there could/should be a weep hole to allow air and some water through?
maybe-not?

I too have not been to my fav Austro Hungarian region in years. Though went back a second time 15 years ago as I figured I would move there.

again, thanks all and etc…

 

[PCH]

But that type only interrupts the coolant flow to the heater core. In a 7/9, the heater core is permanently in the cooling circuit until one presses the recirculation switch, and then vacuum operates the tap. Cabin temp regulation is done in 7/9s by flaps in the HVAC, not by regulating the coolant flow to the heater core.

You wouldn't want to engage "recirculation" in hot weather with that type of tap. It cuts off the coolant flow between the water pump pipe and the back of the head.

Which is why my grandpamobiles all use heater taps that do this, because OZ has always had stupid high summer temps, like many USA folks are getting now.

This type of tap also has the advantage that when the heater core craps out and starts leaking, you can just jam the tap on so coolant bypasses the heater core, then you can top up the coolant and it will get you home.

Another GM valve that allows re-circulation at all times: https://turbobricks.com/index.php?threads/7-9-updated-heater-control-valve.246617/
I am only familiar with US version of the factory HVAC and it does completely shut off flow under MAX COLD setting which is probably the worst time to do it.

 

[oldnfast]

I’ve been using the YG136 forever and didn’t have a failure yet. If your concerned about longevity of that one just change it out sooner as preventive maintenance
I recently gifted my 740 to my goddaughter and gave the car a good stage zero first so she’d be good to go for many miles. Since the YG that was in the car was about 10 years old I changed it to be safe and put the still good one with the rest of the spares in the trunk. Cheap insurance

 

[84B23F]

FourSeasons 74603...all metal

Snake Oil...dissect it....requires a rubber diaphragm inside to move plunger (whatever) up/down. All rubber diaphragms break, sooner or later.

 

[h20ham]

maybe, but plastic, Chinese modern plastic breaks and leaks causing mega (not a trump) problems. a leaking diaphragm does what, leaks into the cooling system?

 

[MasterBlaster]

a leaking diaphragm does what, leaks into the cooling system?

If it's just the diaphragm, the valve stops working, and creates a vacuum leak.

If the internal fluid seals aren't perfect, coolant leaks out via the vent holes on the underside or the diaphragm chamber. Of course, that can happen even if the diaphragm is still good.

 

[84B23F]

Chinese modern plastic breaks....

OEMs have parts made in China, so I don't know how a person could determine whats/what in regards aftermarket quality.

On a different topic, VW CV Boots years ago, India use to make some bad boots, due to incorrect rubber compound. A person had to buy USA/European made boots. Here, India had no idea how to do it right...OEMs were not using India to make their boots.

OEM Volvo heater control valves do fail; they need to be replaced periodically. I'd buy a replacement that fits correctly, and if GM/Ford/etc makes one, I'd buy from them.