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Discussion Starter · #1 ·
I've been racking my brain over the routing of this cooling system, this C3 is a recent purchase/project and I'm battling some overheating issues.

I'm thinking this overflow tank (or whatever it is) is just wrong. There is a hose running from the radiator pressure cap over to another pressure cap on the tank, then two hoses that run off that tank to the heater core.

It makes absolutely no sense. Looking at some photos of C3 engine bays I haven't seen anything like this.

I'm thinking of scrapping this thing and putting in a universal tank and leaving the heater disconnected for the time being, hoping that it will cure my overheating problem.

What say you folks? Am I off my rocker or is this completely wrong?

Hose from water pump to intake manifold


Upper radiator hose


Lower radiator hose



Overflow/expansion/whatever you want to call it tank. Notice the hose from one pressure cap to another.


Hoses from mysterious tank to heater core:



 

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the heater core actually helps cooling

it's been so long since I worked on anything that old but I thought the small hose on the W/P went to the heater ?
 

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Discussion Starter · #3 ·
I've read that installing a shut off valve to the heater core can help keep the cabin cooler, I live in the desert so that sounds like something I want to do.

Looking at photos I think the hoses for the heater core will go between the water pump and the intake manifold.

My radiator cap actually popped off the other day. I'm thinking that the pressure is unable to escape properly because the other side of the line doesn't go to a coolant reservoir...just another pressure cap.

I really think that funky reservoir on there was installed by someone who doesn't understand cooling systems, but I want someone to concur with me because I can be wrong.
 

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I cant be sure from pics how you have the hoses .....and that metal tank was used for several model years ..... but the hose from pump goes to top heatercore , the hose from manifold goes to bottom of heatercore , the expansion tank connects inline to pump hose and small hose connects between the rad cap neck and expansion cap..if I m remembering it correctly..been a while.. that system was deleted in favor of a standard type expansion tank. my 81 has the newer version ..you could eliminate that tank, run the hose continuous to heater and install a plastic expansion tank...and yes, install a shut-off valve in the heater hose ..keep the hot water out of the car in summer
 

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Discussion Starter · #6 ·
Thanks for the info.

I think I found what that tank is:

http://www.jegs.com/p/Moroso/Moroso-Cooling-System-Expansion-Tank/744429/10002/-1

I think I'm going to get a universal overflow tank with the hose fitting on the bottom and use that.

I was thinking about this last night and I think my cooling system pressure got so high that coolant seeped out of the hose going from the water pump to the intake, and eventually popped my radiator cap off.
 

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Discussion Starter · #8 ·
Yeah I am thinking that hose from the intake to the water pump really isn't helping anything...

It's just allowing hot coolant from the top of the engine to be easily pulled back in the water pump and through the engine again. That HAS to be creating at least some heat.

I think I will block it off for now.

I'm guessing this was a previous owner's way of bypassing the heater core.
 

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Remove that goofy hose that connects the water pump to the intake manifold. The hose on the top of the intake manifold is supposed to go to the heater core then the return hose goes to the side of the water pump. Then use ONLY an OEM coolant recovery tank as they have a 5 quart capacity; about twice as much as auto parts store tanks.
 

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Discussion Starter · #10 ·
I already ordered a small overflow tank for $9 from amazon because it'll be here Friday and I want to get it on the road this weekend if I can. I found some sources that sell the OEM type recovery tank for about $35, I may change it out later.

From what I've read, I should be able to get some 1/2 NPT plugs (simliar to the plug you can see to the right of the thermostat housing on my intake manifold) and eliminate that hose altogether. I think what I'll do is pull the fittings off and go down to the auto parts store and get some plugs that match.

This will leave me without a heater, but I can always change it later when it starts to get cold. I have until November to worry about that :)
 

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Coolant Recovery Tanks

I already ordered a small overflow tank for $9 from amazon because it'll be here Friday and I want to get it on the road this weekend if I can. I found some sources that sell the OEM type recovery tank for about $35, I may change it out later.

From what I've read, I should be able to get some 1/2 NPT plugs (simliar to the plug you can see to the right of the thermostat housing on my intake manifold) and eliminate that hose altogether. I think what I'll do is pull the fittings off and go down to the auto parts store and get some plugs that match.

This will leave me without a heater, but I can always change it later when it starts to get cold. I have until November to worry about that :)

I had been running a 2-quart coolant recovery tank in my big block '71 for the past 3 years but it just wasn't big enough for my 20 quart system (big block with a 4 tube radiator). In the cooler months it was big enough but once the weather warmed it wasn't big enough as my radiator would puke out over 2 quarts on a hot shut off. So with each hot shut off I lost about 1 quart.

So I just installed a 5 quart OEM tank designed for the '73's up to '78 and that did the trick as I don't lose any coolant now. It only cost $24 from Rik's.

It does no good whatsoever to run a hose from the intake manifold to the suction side of the water pump as all that does is prevent that much coolant from going thru the radiator. So either connect the hoses to the heater core like they're supposed to be or plug them off. The 5/8" hose coming from the intake manifold is the "hot" hose and the larger 3/4" hose coming back to the water pump is the "return" hose.
 

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Discussion Starter · #12 ·
Ah thanks for sharing your experience. I'm definitely not dismissing the idea of putting an OEM overflow tank in.

I wonder if leaving my electric fans on for 30-60 seconds after a shutoff will help. I think it would be really really cool to have an electric water pump too, and be able to run the entire cooling system with the engine off.
 

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electric waterpumps are for racing..stick with a mechanical pump for reliability ..but, get that little hose out of there.. you re circulating hot water ... and nothing wrong with the fans running a few seconds after shutdown.. my Supercharged T-bird does that in hot weather .... you should be able to run your car in hot climate without overheating.. my engine is way more radical than yours and I can run my A/C on 100+ degree days in traffic,with no overheating whatsoever.
 

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Ah thanks for sharing your experience. I'm definitely not dismissing the idea of putting an OEM overflow tank in.

I wonder if leaving my electric fans on for 30-60 seconds after a shutoff will help. I think it would be really really cool to have an electric water pump too, and be able to run the entire cooling system with the engine off.

It's also very important to maintain a 50/50 mix of antifreeze and water as that will raise the boiling point to 260 degrees. You can buy inexpensive antifreeze testers from any auto parts store.
 
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