1996: run cooling system at no pressure?

[Doug5529]

I have a 1996 that has had multiple issues with the cooling system--usually starting with leaks (leaky plastic-tank radiators, for which there is no practical alternative). Lately it occurs to me that these issues could have ALL been avoided if there was no pressure in the cooling system at all.

Its is to the point that it's not worth fixing anything by the book now. (-Or, fixing it AGAIN I should say) The radiators (no matter where I got them from) simply don't hold the pressure they should. This vehicle is a daily driver, nothing special. It is only worth keeping if it can be maintained cheap, and I've already gone through a few times with major repair bills due to a loss of engine coolant.

In the past I looked for a lower-pressure radiator cap and couldn't find any. I even pondered trying to modify a 16 psi cap to hit a lower pressure, but never did.

I have seen some older cars where people did this (run the coolant system at zero pressure), does anybody do it with these engines? I know that this increases the likelihood of overheating--but then, so does all the coolant leaking out in a month. I don't ever tow anything and live in IL (no mountains).

 

[koda2000]

the system doesn't create the pressure, heating the water does. unless you can reduce the water temp to something really low (like maybe 150 F or less and keep it there) you're not going to have zero pressure and you won't get any heat in the winter. not really practical and you'd need a much larger expansion/overflow tank.

 

[rs2k]

I think you'll get steam in the heads if you try that. It would lead to overheating. The pressure keeps the boiling point of the coolant higher.

If you ran a 160 thermostat it would work. I think you'd still have leaks though.

 

[Runnin'OnEmpty]

.......In the past I looked for a lower-pressure radiator cap and couldn't find any. I even pondered trying to modify a 16 psi cap to hit a lower pressure, but never did.......

You can cut a half coil off the pressure cap spring to
give about 7-10 psi pressure. I've used a small file to
score the spring, and then break it off using needle-
nosed pliers.

If you use a lower pressure cap, you should also install
a 160-180 degree thermostat. Add a bottle of 'Water-
Wetter' to the coolant and you're ready to roll...

 

[my98nnj]

Your trying to put a bad band aid on a problem. That's not the fix.
What's leaking? Hoses, gaskets or the radiator itself? You cannot run them at zero, air pockets will form and your likely to blow a head gasket. Even if you reduce the pressure to 7 or 10 psi you still have a leak.

The plastic radiator in my 98 was original when I sold the truck this spring. The plastic radiator in my 99 Nissan lasted 13 years and 200k miles. Their cheap and easy to replace too. Fix the leak, replace the broken parts or you will continue to throw good money onto bad components.

 

[Bobmbx]

It all depends on where the leak is. My 06 radiator has a leak somewhere at the top. When I refill the radiator and the expansion tank, it'll dribble out for a week or two, then stop. The level in the radiator, at that point, is just below the fill cap, meaning the only fluid I'm really losing is what would be in the expansion tank, not the recirculating system.

I've been running like that, with no pressure, for almost two years. And the temp gage stays right where it's supposed to be. Now, if your leak is at a much lower point you'll lose much more fluid than I am, you'll lose cooling capacity and eventually overheat.

Why do I do that? Simply, I don't feel like handing over a couple hundred bucks to fix something thats not a problem.

I've driven roughly 65k miles like that. Never had an issue.

 

[Doug5529]

Your trying to put a bad band aid on a problem. That's not the fix.
What's leaking? Hoses, gaskets or the radiator itself? You cannot run them at zero, air pockets will form and your likely to blow a head gasket. Even if you reduce the pressure to 7 or 10 psi you still have a leak.

The plastic radiator in my 98 was original when I sold the truck this spring. The plastic radiator in my 99 Nissan lasted 13 years and 200k miles. Their cheap and easy to replace too. Fix the leak, replace the broken parts or you will continue to throw good money onto bad components.

I don't make the radiators, and they usually do work okay in most vehicles.
I've just seen a bunch in this truck all fail in exactly the same way. All from pressure.
And I'm not the only one.

I think I've put about 6 radiators into this thing in 8 years now. A couple times I did it myself, but the other times was pro shops doing it. In my experience, usually the radiators fail (the drivers-side plastic tank bulges out, and lifts off the o-ring seal where it bulges) in the coldest part of winter. Other people on here get the same thing during the hottest part of summer. After this happens the radiator can't be fixed (it is crimped together) and for this type of leak, stop-leak does nothing.

The whole cooling system has been 'repaired' multiple times, by several different shops, including the dealer once and a radiator-only shop once. It never holds coolant more than a few months. I have to check it every week. And the temp gauge bounces up and down too, so that is no help (nobody has been able to fix that either).

When it has a leak and I'm just adding coolant every few days, then its not running at full pressure--there is no way that it can be.
It's also not even running full of coolant, since some leaked out onto the ground as the engine got hot--and it doesn't suck any more in until you stop driving it and it cools down again....
And yet the overheat light never comes on.
Which means that due to the way I use it, it isn't overheating even with lower-than-normal pressure and coolant.
So the next question is, how much pressure does it really need?
The problems I have had were due to coolant loss, not the engine overheating. With no pressure in the cooling system, there would be drastically less coolant loss.

-------

This truck would have had a great maintenance record were it not for the cooling system issues. And repairing it by the book doesn't work for longer than maybe 6 months. That's about how long it takes me to start seeing coolant loss from the reservoir tank.

 

[rs2k]

Are you using the same cap on each radiator? The pressure is controlled by the cap. Or is something clogging the radiators?

 

[Doug5529]

Are you using the same cap on each radiator? The pressure is controlled by the cap. Or is something clogging the radiators?

I think every time it was fixed in a shop, they also got a new cap.
And I bought at least one along the way also.

One shop took apart one of the bad radiators to look inside, and it was perfectly clean. There was no stop-leak of any kind used in it, not by me or anyone else.

 

[thorney_5]

http://www.evanscooling.com/

Many use it for classic cars, but I don't see why it can't be used here. With no water, there is much less pressure. The only disadvantage I see is if you need to do a big repair on the engine, you will have to drain the expensive lifetime coolant.

 

[bill06447]

Very odd....is the overflow tube plugged? Belt routed around the water pump correctly? Head gaskets sound? Forget the snake-oil cooling system band-aid additives, if there's an odd pressure spike causing the radiator to rupture, all a no-pressure cap will do is allow your coolant and high priced soapy water additive to piss out the top. Find a competent shop that will rig a pressure gage to your radiator and see whats going on there.

Bill