No Pressure In Coolant System and Not Overheating?

[The_Eric]

No- not a pump.

If a system were properly filled and bled of air, simply heating it will cause a pressure build up- you don't need a pump to do that. You've got air in there somewhere- the air creates a dead space of sorts and allows for too much room for expansion- so no pressure build up.

 

[The_Eric]

If it were a pump, it'd overheat. You wouldn't be able to drive for several hours without one (working).

 

[zzyzzx]

You said it has a new thermostat, what brand?

 

[TFB1]

Originally Posted By: tony1679
Update - I rented a coolant pressure tester. I first checked the old cap. It wouldn't hold any pressure at all. The new one holds steady. Then I attached the pressure tester in place of the cap, pressurized the system, and left it for an hour. When I returned, it was exactly where I left it, 16psi. Both radiator hoses were solid as a rock, as well as both heater core hoses. I am not calling this proof, but rather a good indicator that there aren't any clogs in the system.

So if the system holds pressure, the cap is proven to be good, the thermostat seems to be working properly, and heat (but not pressure or flow) is being distributed throughout the system, what is wrong?

Surely this has to be the water pump...?


Did anyone fully read this post?????

Pressure issue is apparently fixed, now you need to repair the heater... Forget the pump, almost never cause a circulation problem(and if were problem heater hoses won't both be approx same temp)... In 49 years of owning vehicles I've seen two that would not pump(impellers deteriorated), both those were on mid '90s Aerostars...

 

[SHOZ]

Most pumps now have plastic impellers. If you want to see if there is any circulation, drain some coolant out of the pressurized over flow, then start the engine. It should be pushing coolant through the tank all the time.

 

[TFB1]

Originally Posted By: SHOZ
Most pumps now have plastic impellers. If you want to see if there is any circulation, drain some coolant out of the pressurized over flow, then start the engine. It should be pushing coolant through the tank all the time.


Can't see flow in the 4.6 Grand Marquis/Crown Vic, tank feeds to bottom radiator hose(and why it is self bleeding once running)...

 

[SHOZ]

Originally Posted By: TFB1
Originally Posted By: SHOZ
Most pumps now have plastic impellers. If you want to see if there is any circulation, drain some coolant out of the pressurized over flow, then start the engine. It should be pushing coolant through the tank all the time.


Can't see flow in the 4.6 Grand Marquis/Crown Vic, tank feeds to bottom radiator hose(and why it is self bleeding once running)...
Isn't there a smaller hose going into the tank? This usually comes off the heads somewhere.

 

[TFB1]

Yes you are correct, small hose feeds into side of tank that has a baffle so can't see much...

 

[SHOZ]

That's why you need to drain that tank. It will fill up right off the bat if there is flow. Or at least you will see the coolant coming in and going out the bigger hose to the LRH.

 

[tony1679]

TFB1 - Let me clarify my last post:

"Update - I rented a coolant pressure tester. I first checked the old cap. It wouldn't hold any pressure at all. The new one holds steady (when testing with the pressure tester directly on the cap only). Then I attached the pressure tester in place of the cap, pressurized the system, and left it for an hour. When I returned, it was exactly where I left it, 16psi. (Which means the system holds pressure via the pressure tester, as well as the cap, but when the cap is placed back on the tank, there is still no pressure). Both radiator hoses were solid as a rock, as well as both heater core hoses. I am not calling this proof, but rather a good indicator that there aren't any clogs in the system.

So if the system holds pressure (artificially), the cap is proven to be good, the thermostat seems to be working properly, and heat (but not pressure or flow) is being distributed throughout the system, what is wrong?

Surely this has to be the water pump...?"
Originally Posted By: TFB1
Did anyone fully read this post?????

Pressure issue is apparently fixed, now you need to repair the heater... Forget the pump, almost never cause a circulation problem(and if were problem heater hoses won't both be approx same temp)... In 49 years of owning vehicles I've seen two that would not pump(impellers deteriorated), both those were on mid '90s Aerostars...

 

[tony1679]

Well, after reading all of your responses, I will bleed the system. I'm pretty sure this is not the issue, but it is still a variable and needs to be eliminated. After a bleed, if I still have this problem what's next, heater issue or water pump? I was under the impression the heater problem is unrelated to having coolant pressure....

 

[rslifkin]

Did you put the pressure tester on the system with it hot? If not, I'd try that and see if it leaks down. Could be that it starts to build pressure, but then loses it when something gets hot and stops sealing.

 

[tony1679]

Originally Posted By: rslifkin
Did you put the pressure tester on the system with it hot? If not, I'd try that and see if it leaks down. Could be that it starts to build pressure, but then loses it when something gets hot and stops sealing.
I did not, I thought you weren't supposed to. I guess it's worth a try after I bleed it. If this happens, what could that be? I'm 99% positive I don't have a head gasket issue.

 

[sleddriver]

So you determined the cap leaked, OK. One down.

You pressurized the system, for only an hour, and it didn't leak down. So pressurize it when it's hot, and leave it for much longer...5 hrs. Then check the psi gauge again.

What's the highest point in the cooling system?

 

[TFB1]

Originally Posted By: tony1679

So if the system holds pressure (artificially), the cap is proven to be good, the thermostat seems to be working properly, and heat (but not pressure or flow) is being distributed throughout the system, what is wrong?


Likely nothing, if it doesn't make pressure and has no leaks you are defying laws of physics, no if and or buts... Coolant expands when heated, will build pressure even if there is some air in system, end of story... From stone cold take it out for a 20-30 minute run, now that it has a good cap I'm betting it builds pressure... If it has a bad water pump or excessive air in system it's going to over heat(so don't venture too far from home)...

The easiest way to be sure most air is out of system is with engine off, remove upper heater hose on intake and add coolant until it dribbles out of intake... Do this while holding heater hose just high enough so there is no flow from it, reconnect hose, done...

 

[zzyzzx]

I still want to know what brand of thermostat was used, since if you put in a Motorad, it's probably stuck open.

 

[tony1679]

Originally Posted By: zzyzzx
I still want to know what brand of thermostat was used, since if you put in a Motorad, it's probably stuck open.
I used a "Superstat" theromostat. Advance Auto Parts part #45779. Backed by a lifetime warranty, so I'm not concerned if it presents a problem. The Motorad that was included with the new intake remains on my cold, dark, lonely garage shelf. Right where such a despicable thing belongs

. (In case I wasn't clear, I share your Motorad dislike. I learned the hard way on one of their caps on the SS, installed by the previous owner.)

 

[tony1679]

Originally Posted By: sleddriver
What's the highest point in the cooling system?
The cap is the highest point.
Originally Posted By: TFB1
Likely nothing, if it doesn't make pressure and has no leaks you are defying laws of physics, no if and or buts. Coolant expands when heated, will build pressure even if there is some air in system, end of story.
I'm not saying you're wrong, but that is exactly what has been happening.

I promise I'm not calling you a liar and I'm not getting irritated wih you at all. I'm just trying to present the evidence I see. I really do appreciate your help.
Originally Posted By: TFB1
From stone cold take it out for a 20-30 minute run, now that it has a good cap I'm betting it builds pressure. If it has a bad water pump or excessive air in system it's going to over heat
This was done days ago. I drove it for two hours. Same cap, same coolant, same result. No pressure, no flow, no leaks, no overheating. Before you respond though, read my next post.

 

[tony1679]

Update - I did NOT bleed the system, nor did I even touch the water pump. I simply got in the car today to go get a few groceries, and so that I could pressure test it while hot. When I got home, I was shocked!

The upper radiator hose had pressure! So did the lower, and both of the heater core hoses. Now, let me clarify, it was not the same amount of pressure as when the pressure tester was at 16psi, but I would guess it was around 10-12. The hose was firm, but if I really tried I could squeeze maybe 1/4 of the way through. Even better, the radiator hoses were actually full of fluid.

So what happened? I'm confused. The only thing I can think of is that the pressure tester pushed a trapped air pocket?

Regardless, the system now has pressure (a decent amount anyway). I'll monitor it over the next few days and remove the cap every time it cools down to allow any air to escape, as the reservoir is completely full. I did that per rslifkin's advice. As long as nothing changes over the next few days, I will finally go get a coolant flush. Yes, I'm having a local radiator shop do it. They do a real flush (high pressure), much better than I can do at home, and charge a very fair price.

Thanks again, and I'm looking forward to reading your responses.

 

[Lubener]

Air in the system will usually work its way out to the bottle. Air will become an issue if the thermostat is at the highest point in the cooling system. The air pocket gets trapped behind the theromostat. The engine can overheat. Many stats have a small bleed hole in them or you can drill a small one to combat this. I doubt an air pocket caused your no pressure/heat issues.