Coolant overflow hose

[Jeff753]

I started dripping antifreeze out of a hose that goes from the top of the Cummins 350ISC to the top of the coolant overflow tank. I took it off and found the barb on the tank is about.

.338" but the Id of the hose is about .412"?
I guess I'll find an adapter and short piece of hose that fits the barb on the coolant recovery tank?
I guess this hose is not under pressure? It is higher than where it exits the top of the motor though I haven't taken it off the motor side...it looks like that's why the hose is is larger to fit the motor barb.
What is the function of this hose anyway?

[palehorse89]

Hello Jeff, on mine, that small hose that comes out of the block near the thermostat housing goes to the "Surge Tank", then another on just like it comes out of the Surge Tank and goes to the steel piping coming out of the thermostat housing (Upper Radiator Hose) going to the radiator into a "Tee" and out of the other side of the Tee is another small hose going to the top side of the radiator. These are a braid covered hose, and have to take the coolant system pressure and temps.
From what I can tell, when you start the engine, and the thermostat is closed for some time, those hose's have coolant being pushed through them as the water pump is turning on the block side pushing the coolant up and out that small hose on the block and circulating it and pre heating the coolant in the surge tank and the radiator, as they start to get warm, and heat up everything before the thermostat opens............till the thermostat opens up.........but there is still a flow through them. The only hose that goes to my plastic "Over Flow Tank" is the one on the neck of the surge tank, and when the thermostat opens, the coolant from the surge tank expands and flows to the over flow tank, and when it cools down, it sucks the coolant back out of the over flow tank back into the surge tank, and the over flow tank should always maintain the same level when cold, other wise there is a leak in the cooling system somewhere.
Hope this helps you out.......Happy 4th of July!
(Click on photo to enlarge and Zoom in)
PS, the hose in your first and second photo looks like gas line hose........?

[Jeff753]

I believe you are correct that it must be gas line hose. What hose should it be? On the top of my overflow tank I have two fittings that go into the top of the tank. One is from next to the thermostat housing and one from the top of the radiator. They are not the same typehoses. One looks like gates fuel line and one looks like poly lined boat fuel line??
I also have an overflow tube at the neck of the tank and a 1 1/2" or so outlet hose at the bottom of the tank that goes into the lower radiator hose (I think). So I have 4 hoses to the tank.
What should the overflow hose from the thermostat housing be?
I'm going to pull it from the engine side and see if the hose is too big for the barb on both ends or just the end at the overflow tank. I'm surprised it didn't leak before. It's like 3/8" barb and a 1/2" Id (measures .421") hose. Looks like fuel line. The smallest Gates coolant hose I see is 1/2".

[palehorse89]

Just a question, I am guessing that you do not have a surge tank like in my photo? just a over flow tank Jeff?
Up high, you can see my surge tank with the yellow label on it and down to the right, you can see my over flow tank.
Edit: Looking again, you just have a plastic surge tank I believe..........with a radiator cap on it? I wonder how it relieves itself when the cap opens when heated up? The coolant will have to go somewhere, so the system can maintain the pressure of the cap........when the coolant expands. Does the coolant level go up and down in the tank as it heats up and cools down, high/low level marks on it?

[Jeff753]

I just have the plastic overflow tank with 4 connections to it. One comes from by the thermostat housing in the photo above. That is the one that is leaking as the barb on the tank is smaller than the Id of the hose. Another inlet on the top of the tank is from the top of the radiator. The third is the simple overflow next to the neck on the tank (it has a 10# cap) and the fourth line is a 1 1/2" pipe from the bottom of the surge tank to the radiator line (bottom hose).
I need to figure out what the line should be from the engine overflow to the surge tank.

[palehorse89]

I am going to say that you are going to have to change the fittings cause their size seems odd, to a 3/8" barbed fitting so you can buy a good quality heater hose. The local parts store or hardware store had ought to have the fitting's. And then get some heater hose something like this " Silicone Heater Hose with 3/8" Inside Dia., Blue

and replace the hose's that have been replaced with gas line.

[jacwjames]

I had to change my surge tank due to cracking. When I did this I had to pull the small hoses off the old tank. When I installed the new tank I tried to reinstall the small hoses but found the one coming from the engine to be hard and brittle. I decided to change so I took a piece of the old hose to Autozone and they matched it up with a braided hose. I believe it was 1/4" hose.

When I completed the installation I was checking all the connections. At first I did not have the radiator cap on to limit pressure. While the engine was running I looked in the tank and saw that the small hose I had changed carried a large flow of coolant to the tank, indicating that it did have pressure behind it. Didn't notice how long it ran like this.

[Jeff753]

Okay I found some Gates 3/8" heater hose at oreilys. Looked for the green stripe but they didn't have it. It fit the top of the motor barb perfectly but was too big for the barb on the tank (apx .321"). I used two SS clamps on each end. Started it up with the cap off. There is definitely a flow from the motor into the coolant tank. No leaks! . Buttoned it up and calling it done for now. I may change the fitting into the top of the tank to a 3/8" barb but I'm on the road and don't like to mess with things that aren't broke on the road.
I guess heater hose will suffice

[palehorse89]

Glad you got it fixed up Jeff ! Thanks for the update!
Safe travels to ya and enjoy!