Subie Cooling Problem Solved?

[ArdWrknTrk]

Well, it ain't fixed.

And I'm also going to pull the hose from the radiator's neck to the expansion tank and make sure it doesn't have any leaks.

Anybody with better ideas?

I don't know about it being a better idea, but here goes. If you did not find any leaks in the hose going to the expansion tank [I assume not as you did not report doing so], then maybe there is a blockage inside the tube? Perhaps under higher pressures [16+ psi], hot coolant can get by the blockage, but at lower pressures, the blockage is such that what is in the reservoir cannot be drawn back and a few psi is maintained above the cap, preventing the cap from being able to operate as designed?

If the coolant cools down, it MUST become a smaller volume.

If some is displaced, there necessarily is less volume.

There's no way I know that less volume in a closed system at a given temperature can be under pressure.

According to the laws of our known universe it cannot work that way.

But we DO have some data.

So it's time to investigate rational explanations

[Gary Lewis]

I'd think the system would have to develop negative pressure (if the overflow is at atmospheric) to suck coolant in.

Hydraulics behave a certain way.

For a full system to have positive pressure after discharging some fluid and cooling back down, defies physics

Jim - I'm in total agreement. It defies something. The implication is that it isn't getting cool enough with the cool down. But we didn't use to have this problem, even in the summer.

I don't know about it being a better idea, but here goes. If you did not find any leaks in the hose going to the expansion tank [I assume not as you did not report doing so], then maybe there is a blockage inside the tube? Perhaps under higher pressures [16+ psi], hot coolant can get by the blockage, but at lower pressures, the blockage is such that what is in the reservoir cannot be drawn back and a few psi is maintained above the cap, preventing the cap from being able to operate as designed?

David - Interesting idea. So I just pulled a cleaning brush through the hose and only got a few fibers that were probably from the string I used to pull the brush. And, I ran a q-tip through the port in the radiator's neck, but there wasn't much in it either.

Thanks, guys. But I'm

[Gary Lewis]

If the coolant cools down, it MUST become a smaller volume.

If some is displaced, there necessarily is less volume.

There's no way I know that less volume in a closed system at a given temperature can be under pressure.

According to the laws of our known universe it cannot work that way.

But we DO have some data.

So it's time to investigate rational explanations

Yes! I'm I'm asking for y'all to come up with those rational explanations 'cause I'm all out.

[1986F150Six]

I'd think the system would have to develop negative pressure (if the overflow is at atmospheric) to suck coolant in.

Hydraulics behave a certain way.

For a full system to have positive pressure after discharging some fluid and cooling back down, defies physics

Jim - I'm in total agreement. It defies something. The implication is that it isn't getting cool enough with the cool down. But we didn't use to have this problem, even in the summer.

I don't know about it being a better idea, but here goes. If you did not find any leaks in the hose going to the expansion tank [I assume not as you did not report doing so], then maybe there is a blockage inside the tube? Perhaps under higher pressures [16+ psi], hot coolant can get by the blockage, but at lower pressures, the blockage is such that what is in the reservoir cannot be drawn back and a few psi is maintained above the cap, preventing the cap from being able to operate as designed?

David - Interesting idea. So I just pulled a cleaning brush through the hose and only got a few fibers that were probably from the string I used to pull the brush. And, I ran a q-tip through the port in the radiator's neck, but there wasn't much in it either.

Thanks, guys. But I'm

 

David - Interesting idea. So I just pulled a cleaning brush through the hose and only got a few fibers that were probably from the string I used to pull the brush. And, I ran a q-tip through the port in the radiator's neck, but there wasn't much in it either.

Thanks, guys. But I'm

Okay... now, how about the reservoir, itself. Could there be junk in the bottom, where the hose connects?

[Gary Lewis]

 

David - Interesting idea. So I just pulled a cleaning brush through the hose and only got a few fibers that were probably from the string I used to pull the brush. And, I ran a q-tip through the port in the radiator's neck, but there wasn't much in it either.

Thanks, guys. But I'm

Okay... now, how about the reservoir, itself. Could there be junk in the bottom, where the hose connects?

I don't think so, but I'll check........

[Gary Lewis]

I don't think so, but I'll check........

Nope. This is the coolant from it, and the reservoir is quite clean. Plus, the hose is cut at an angle at the bottom so shouldn't be able to seal against the reservoir. And, it has been out several times - with the same results each time.

But, keep those ideas coming, folks. Please!

[1986F150Six]

Nope. This is the coolant from it, and the reservoir is quite clean. Plus, the hose is cut at an angle at the bottom so shouldn't be able to seal against the reservoir. And, it has been out several times - with the same results each time.

But, keep those ideas coming, folks. Please!

Since there has now been several caps [3?], and the likelihood that all the caps were defective is low [I would think; especially since some were from one source and one was OEM], what if there is a crack or defect in the radiator mouth, where the cap rubber seal mates? Could the pressure in the radiator push the coolant to the expansion bottle, and as the radiator/coolant cooled down, if the rubber seal could not properly seal due to the radiator neck defect, maybe air would be sucked in rather than coolant from the reservoir?

[Gary Lewis]

Since there has now been several caps [3?], and the likelihood that all the caps were defective is low [I would think; especially since some were from one source and one was OEM], what if there is a crack or defect in the radiator mouth, where the cap rubber seal mates? Could the pressure in the radiator push the coolant to the expansion bottle, and as the radiator/coolant cooled down, if the rubber seal could not properly seal due to the radiator neck defect, maybe air would be sucked in rather than coolant from the reservoir?

Actually there have been four caps in the last month:

• #1: The one that had been on for a looooong time. Probably a Stant as that's what I used to buy. May not have been bad as the car was exhibiting the same symptoms as it is now.

• #2: The bad Stant that the mechanic found bad when he ran out of other things to check

• #3: The new Stant that is now in the glove box. Gave the same symptoms as #1 and #2.

• #4: The Subaru cap, new as of yesterday, and gives the same symptoms

So it isn't the cap. But I can't feel nor see anything wrong with the radiator's neck. And the caps seal fine up until the cap opens up, just as they should. They just don't let the coolant come back in.

It is as if the engine isn't getting cool enough at night, and the cold water this morning didn't do it. Was just in the parts store and talked to DeWayne and he said his 7.3 IDI still has pressure on it in the mornings now. Am I chasing shadows?

Just added 1 can of R134a, and idled the thing for an extended time, then drove it to the parts store, left it idling, stopped at Walmart and left it idling, and came home and added another 1/2 can of 134a. And the thing didn't push any coolant out while it was running. May now that I shut it off, so we shall see. But it cools very, very well. Just can't keep it full of coolant.

[85lebaront2]

Nope. This is the coolant from it, and the reservoir is quite clean. Plus, the hose is cut at an angle at the bottom so shouldn't be able to seal against the reservoir. And, it has been out several times - with the same results each time.

But, keep those ideas coming, folks. Please!

Another explanation you probably don't want to hear, actually two, (a) water pump seal that leaks when stationary under reduced pressure (in) or (b) head gasket(s) leaking forcing coolant out then since it wasn't expansion not pulling it in.

Third would be a similar situation anywhere there is a joint in the cooling system and from what I remember from the Subaru I had and others I have messed with, only a V12 E-Type Jag has more joints. and they could be a nightmare to get sealed.

[Gary Lewis]

Another explanation you probably don't want to hear, actually two, (a) water pump seal that leaks when stationary under reduced pressure (in) or (b) head gasket(s) leaking forcing coolant out then since it wasn't expansion not pulling it in.

Third would be a similar situation anywhere there is a joint in the cooling system and from what I remember from the Subaru I had and others I have messed with, only a V12 E-Type Jag has more joints. and they could be a nightmare to get sealed.

Bill - Thanks, but there are no products of combustion in the coolant, so don't think it is head gasket. And we don't lose any coolant. It pushes it out to the expansion tank and if you bring it back the radiator is completely full. So I'm pretty sure there aren't any leaks.

Besides, it sat for 7 hours at 15 psi and didn't lose any pressure. In fact, it'll sit over night and still have some pressure the next morning, which explains why it isn't pulling coolant back in.

Just checked and today's extensive idling with the A/C on as well as a trip to town didn't push any coolant out. The temp gauge never bobbled. I'll check it again in the morning to see if it still has pressure on the system.