Purpose of this Valve?
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Scarpa
- Posts: 20
- Joined: Sun Mar 19, 2023 11:57 pm
- Your car is a: 1981 SPIDER
Purpose of this Valve?
Can someone explain to me this valve being on this hose? I've checked the mechanics manual for my 81 Spider, and its not there.
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Akspider
- Patron 2019
- Posts: 21
- Joined: Mon Oct 29, 2018 7:05 pm
- Your car is a: 1972 124 Spider
Re: Purpose of this Valve?
I'd venture to say it's to cut off coolant (hot water) to the heater core. Pretty sure bet it's a previous owner install you won't find in the manuals.
Anchorage, AK
2013 Kia Sorento (gets me to the parts store)
1972 Fiat 124 Spider (Fix It Again Tomorrow (maybe)!)
1966 Comet Caliente Convertible (the fair-weather summer cruiser)
2013 Kia Sorento (gets me to the parts store)
1972 Fiat 124 Spider (Fix It Again Tomorrow (maybe)!)
1966 Comet Caliente Convertible (the fair-weather summer cruiser)
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18Fiatsandcounting
- Posts: 3798
- Joined: Fri Mar 15, 2019 11:23 pm
- Your car is a: 1969 and 1971 124 spiders
- Location: San Francisco Bay Area
Re: Purpose of this Valve?
Yes. That hose is the supply side of the heater core, so the previous owner installed this valve to cut off coolant to it. The reason is often that the heater core leaks (or the valve next to it), and this is an easier "fix" than replacing the heater core.Akspider wrote:I'd venture to say it's to cut off coolant (hot water) to the heater core. Pretty sure bet it's a previous owner install you won't find in the manuals.
-Bryan
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spider2081
- Patron 2024
- Posts: 3015
- Joined: Fri Jan 27, 2006 11:45 pm
- Your car is a: 1981 Spider 2000
- Location: Wallingford,CT
Re: Purpose of this Valve?
In addition to both previous replies:
The factory heater valve mounted to the heater core shuts off the coolant to the heater core it does not shut of coolant from the heater core back to the engine. If the engine is run for a long period of time on a hot day the heat from the engine coolant can heat the core to a lesser degree than if the factory valve is opened. To avoid this some people install a manual shutoff in the hose that returns coolant to the head. This prevents coolant heat transfer into the core. Some suggest installing this valve causes a hot spot in the head that can lead to head gasket failure.
Many later model cars install a heater bypass valve especially if the car has factory air conditioning. These valves often have 4 hose connections and return the coolant through the head without any fluid reaching the heater core. Usually mounted in the engine compartment.
The factory heater valve mounted to the heater core shuts off the coolant to the heater core it does not shut of coolant from the heater core back to the engine. If the engine is run for a long period of time on a hot day the heat from the engine coolant can heat the core to a lesser degree than if the factory valve is opened. To avoid this some people install a manual shutoff in the hose that returns coolant to the head. This prevents coolant heat transfer into the core. Some suggest installing this valve causes a hot spot in the head that can lead to head gasket failure.
Many later model cars install a heater bypass valve especially if the car has factory air conditioning. These valves often have 4 hose connections and return the coolant through the head without any fluid reaching the heater core. Usually mounted in the engine compartment.
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Spider951
- Patron 2020
- Posts: 131
- Joined: Mon May 29, 2017 8:44 am
- Your car is a: 1981 Spider 2000
- Location: Tuscaloosa, AL
Re: Purpose of this Valve?
As a variation of the above, I installed a fitting with a removable cap (yellow arrow in photo) to help with "burping" the air out of the system when needed. (I later shortened the hose on the right side - it didn't need to be quite that high to be the highest point in the system for air removal). The heater core was leaking, and I just chose to remove it from the loop (not many days here that I even need heat - mostly the opposite!!!).
