need help finding a part
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need help finding a part
I Have a 73 olds ninety-eight and starting to restore and i broke a part which i believe is a temperatue vacuum switch or thermal vacuum switch checked everywhere. any suggestions
Registered User
Joined: Jun 2009
Posts: 15,116
From: southeastern Michigan
I have a '73 Custom Cruiser, which has the exact same engine as your car. I believe I know just what part you're talking about as I needed a new one for my car as well
The service manual calls it a "thermal vacuum switch." Autozone has them for $25.00. They call it a "ported vacuum switch." (Photo below.) It's a drop-in replacement. If you go to a store, they'll order it as the website shows it as a special order item. You'll get it in a couple of days.
The service manual calls it a "thermal vacuum switch." Autozone has them for $25.00. They call it a "ported vacuum switch." (Photo below.) It's a drop-in replacement. If you go to a store, they'll order it as the website shows it as a special order item. You'll get it in a couple of days.
Registered User
Joined: Jun 2009
Posts: 15,116
From: southeastern Michigan
OK, I think I know what you are talking about. It's called the "Distributor Thermal Check and Delay Valve" and it goes in the vacuum line between the middle port of the thermal vacuum switch and a port on the carburetor.
In my experience, this part is not made now, and no parts supplier I've searched or checked with has it. If yours can't be used, and you can't find either a good used or NOS piece, your only option is to simply run without it and hook the vacuum line directly from the tvs to the carb.
I'm not sure exactly what the "DTCDV" does. The thermal vacuum switch itself is designed to help the engine run cooler when the coolant temperature is high. What happens is that, when the coolant temp is high (the manual says 226 degree F), the valve opens, directing full manifold vacuum to the distributor vacuum advance. This advances the timing, allowing the engine to run cooler. Given its name, I'm guessing the "Distributor Thermal Check and Delay Valve" makes sure that vacuum only goes one way? Isn't this what a check valve usually does? Prevents back flow?
Anyway, like I say, I've run without one for a year now, which is as long as I've owned my '73, and I haven't had any problems. Based on the fact that, when I got the car, it not only didn't have one of these check valves but also didn't have a working thermal vacuum switch, I'm guessing it was driven for I don't know how many miles in this condition with no apparent problems.
In my experience, this part is not made now, and no parts supplier I've searched or checked with has it. If yours can't be used, and you can't find either a good used or NOS piece, your only option is to simply run without it and hook the vacuum line directly from the tvs to the carb.
I'm not sure exactly what the "DTCDV" does. The thermal vacuum switch itself is designed to help the engine run cooler when the coolant temperature is high. What happens is that, when the coolant temp is high (the manual says 226 degree F), the valve opens, directing full manifold vacuum to the distributor vacuum advance. This advances the timing, allowing the engine to run cooler. Given its name, I'm guessing the "Distributor Thermal Check and Delay Valve" makes sure that vacuum only goes one way? Isn't this what a check valve usually does? Prevents back flow?
Anyway, like I say, I've run without one for a year now, which is as long as I've owned my '73, and I haven't had any problems. Based on the fact that, when I got the car, it not only didn't have one of these check valves but also didn't have a working thermal vacuum switch, I'm guessing it was driven for I don't know how many miles in this condition with no apparent problems.
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alan69delta88
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Aug 12, 2006 09:01 AM
