I just finished changing all the up front radiator hoses, balance manifold, thermostat housing to metal a new expansion tank and a new water pump. After filling with coolant and running the engine to warm up there was coolant dripping out the underneath on the left and about where the air conditioner condensation comes out. When I installed the new expansion tank the cap took off to parts unknown behind the engine. I had to use the old cap. I got quite a lot of coolant dripping from somewhere but none around any hoses or the tank that I could find. I got a new cap (I was told the cap could be bad once before) and the problem went away. My question is how does the cap function in a way that can cause this to happen with a new one stopping it?

Can someone explain how this system really works and where is that overflow bottle located?

Thanks guys!

 

Is it leaking on the drivers side? I changed the expansion tank and was getting leaks on the passenger side, where I believe the overflow tank is, I put another cap I had ordered from Rock auto and I still had the leaking, so I put the old cap and it stopped the leaking. I believe the cap allows the overflow tank to siphon the coolant back into the system, but I'm sure minds that are greater than mine will explain

 

is hose going into bottom of the tank snugged down?

 

Yes, it does.

The cap on the pressure reservoir allows coolant to flow into the atmosphere reservoir when the coolant system exceeds about 15 psi which is the normal operating pressure. The valve in the cap also functions to allow the overflow coolant to be siphoned back into the pressure side as the engine cools. The atmosphere reservoir is located behind the right tire. You have to remove the inter wheel well lining to see it.

 

The diagram in JEPC is the clearest:



As the engine warms up, excess coolant passes from the Expansion Tank (item 1) to the Atmospheric Recovery Bottle (item 11) which is behind the RH front wing liner through the Expansion Hose (item 8):



As the engine cools down, coolant is drawn back from the Atmospheric Recovery Bottle to maintain the correct level in the Expansion Tank.

If there is too much coolant in the system and the Atmospheric Recovery Bottle fills, it vents to the ground below through the Overflow Pipe (item 17).

Graham

 

Thanks GGG for the diagram. But, how about this. When I removed the expansion tank, which I left off for several days, the hose attached to the bottom was full of coolant. And it stayed that way for several hours while I did other things. Later I noticed the level had dropped a couple of inches. When I was ready to install the new tank several days later the coolant level could not be seen as I recall. there must be another valve in the recovery tank or when you remove the cap on the expansion tank the coolant would drop instantly.

Interested in your reply.

 

You should have plugged that hose and the bleed hose to the thermostat housing to prevent loss of coolant.



A wine bottle cork fits the bottom hose (arrowed in red) and a 1/4 inch extension drive fits the bleed hose (arrowed in blue). If you don't plug them, gravity will win and you'll lose coolant.

In normal use, coolant is forced to the Atmospheric Recovery Bottle by expansion as the engine heats up and drawn back to the Expansion Tank by vacuum as it cools down.

Graham

 

I had already drained all the coolant from the radiator. I am going to do a complete coolant service after I'm sure all is working as it should.

But back to just the expansion tank and overflow tank. As I mentioned the hose to the overflow tank stayed full for quite sometime. And I mean right to the brim. It did slowly go down over time, several days. There fore there must be some valve in the overflow tank that keeps if from just draining down when the expansion tank is removed or the cap taken off with the tank installed. That is the question that interest me.

Editing! I just went back and looked at your diagram. The hose that you put the wine cork in does not go the the overflow tank!!! Where does it go? It is not shown in the diagram. I think it goes to the heater hose system. So I have been screwed up. The line to the overflow tank is connected to the expansion tank at the top of the tank which will not allow coolant to drain to the overflow tank when the cap is removed. And the overflow tank would normally have air space to handle the drain. Now I'm beginning to wonder if I have leak in the heater system of hoses. THAT I DON'T LIKE THE SOUND OF.

 

YES - it's a heater system hose (see item 10):



It connects through a 'tee' to one of the notorious 'valley' hoses (item 2).

Graham

 

SO, with the rad full and the expansion tank off the coolant would come out of the hose which is why you put the cork in it. Hey, that makes sense now. Duhh I am beginning to think that I have a leak somewhere in that mess of hoses. Any suggestions where it might be?

edit: And that connection has the hose that goes up to the balance plastic manifold, which I just replaced, at the front of the engine that connects to the top of the thermostat housing which I just replaced.

 

One of the 'valley' hoses is certainly a possibility. The problem always is that when you replace one hose, the pressurised cooling system then finds the next weakest.

A pressure test kit could help locate a leak.

Graham

 

Thanks GGG for your help and patience. You have been a great help. I finally understand how this system works.