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Subie Cooling Problem Solved?

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ArdWrknTrk

Re: Subie Cooling Problem Solved?

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If the radiator is full it will always be pushing into the expansion tank (once the hoses balloon)
Just like ice, water is powerful stuff as it heats up, and it is going to go somewhere

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

Yes, but when the system cools it should pull the coolant back into the radiator. And this one didn't.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

Inspecting the Stant cap closely I find that the "vacuum valve", as shown in the drawing below, has a stronger spring on it than I remember from other caps. This leads me to believe that it isn't releasing as the system cools, so coolant isn't sucked back into the radiator.

For those that might not know, here are three snippets from this site on how the radiator cap is supposed to work:

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Subie Cooling Problem Solved?

Administrator

I understand the principal.
I was the one that suggested OEM in the first place.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

I knew you did, Jim. And I expect most people do. Was just explaining in case someone didn't.

And I do remember you recommending OEM. But this car's been running an aftermarket radiator cap for years, so I didn't expect there to be a problem. However, I am sure hoping that's the issue. We shall see.

Also, there's an exhaust doughnut that has given up the ghost, so I'll get one of those while I'm at Subaru tomorrow. And I'll be squirting the studs for the exhaust with penetrating oil today.

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

Time for an update and a plea for help.

Let me try to summarize - the Subie pushes coolant out to the overflow tank, as it should, but doesn't pull it back when the engine "cools". In fact, having sat outside overnight where the temp got down to 80 degrees, and then running cold water from the hose over the engine and radiator for 20 minutes there was still a slight pressure in the system when I pulled the cap. However, the system was down 1 pint from a 75 mile trip where I ran it at 65 - 75 MPH, and frequently into a significant head wind.

Obviously with pressure in the system it isn't going to pull a vacuum and suck the coolant back. But, what would cause the system to still be under a slight pressure?

I'm at my wit's end and need help - in more ways than one!

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Subie Cooling Problem Solved?

Administrator

I do a reagent test for combustion by-products.
Cracks and gaskets can open up under load and close when there is none, or the heads start to cool.

If you don't have any oil in the catch bottle there are few other things it could be.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

According to the mechanic there are no products of combustion in the coolant. And there's no oil in the overflow tank nor radiator. Nor coolant in the oil. Plus, if you carefully put what is in the expansion tank above the Full mark back in the radiator the radiator is full each time, so we aren't losing coolant.

The issue really is why the system is staying pressurized. Not high pressure, but even after sitting overnight and then having cold water run over it for 20 minutes there was still a bit of pressure. So it won't suck any coolant back.

And, on each drive it seems to push more coolant into the overflow, so it isn't long before it is low.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Subie Cooling Problem Solved?

Administrator

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,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

1986F150Six

Re: Subie Cooling Problem Solved?

Administrator

In reply to this post by Gary Lewis

Gary Lewis wrote

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?

ArdWrknTrk

Re: Subie Cooling Problem Solved?

Administrator

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

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

In reply to this post by 1986F150Six

ArdWrknTrk wrote

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.

1986F150Six wrote

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, AKA "Gary fellow": Profile

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

In reply to this post by ArdWrknTrk

ArdWrknTrk wrote

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.

Gary, AKA "Gary fellow": Profile

1986F150Six

Re: Subie Cooling Problem Solved?

Administrator

In reply to this post by Gary Lewis

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

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

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

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

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!

Gary, AKA "Gary fellow": Profile

1986F150Six

Re: Subie Cooling Problem Solved?

Administrator

This post was updated on .

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

Re: Subie Cooling Problem Solved?

Administrator

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.

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: Subie Cooling Problem Solved?

Administrator

In reply to this post by 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 AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

Gary Lewis

Re: Subie Cooling Problem Solved?

Administrator

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.

Gary, AKA "Gary fellow": Profile

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