Pressure in Lower Radiator Hose - Leaking (1 Viewer)

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Aug 11, 2020
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Baton Rouge, LA
I recently replaced all of the cooling system on my '95. That included Denso radiator, denso thermostat, upper and lower hoses, PHH, heater control valve, with all new Toyota Red coolant and distilled water. Everything has been running smoothly for the past couple weeks until I looked underneath today and saw some coolant spray on the front diff and other parts. I thought it might be the placement of the spring retainer on the lower rad (I kept the original clamps) and when I squeezed the clamp to readjust, coolant sprayed everywhere.

That's strange to me. I figured if it was at temp then the pressure should be releasing somewhere else. The only possible thing I can think of is the radiator cap (Stant). My original is corroded or else I'd put it back on. Is there any other reason there would be that much pressure in the hose?

Also, the overflow bottle is down to the minimum mark after two weeks of mild driving. Which means it's probably been leaking for a little bit and it's definitely not putting coolant back in.

Do those oem springloaded clamps need to be aligned just perfectly to seal? Or will this pressure go away with a new rad cap?
 
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Aug 2, 2017
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Tustin, California
Got any photos? I've had a rad separate from the aluminum core a week after install, leaking everywhere. Could have a pinhole leak or something in a hose that was now found with by fixing coolant leaks.
 
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I think I'll also buy the OEM radiator cap as well. The Stant was a tight fit on the new Denso rad. It's $20 and worth insuring a proper pressure in the cooling system.

I'm also thinking this may be because I accidentally swapped the two spring clamps on the lower rad hose. I was pretty careful not to do that when reinstalling, but there's always the chance I mixed them up. I read that those two clamps are different IDs and can cause improper sealing.
 
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I figured if it was at temp then the pressure should be releasing somewhere else.
I'm not sure what this sentence means.
At normal operating temperature, there should be pressure throughout the cooling system that is regulated by the radiator cap.
The pressure decreases as the engine cools and there should be virtually no pressure in the system with a cold engine.

However, even with a cold non running engine, the lower radiator hose holds the static weight of the fluid capacity of the system.
 

Nframe

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Dec 26, 2018
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Wisconsin
I have the same issue with the system remaining pressurized long after the engine cools.
Any weak spots in the cooling system will slowly seep slight amounts of antifreeze. At first coming from the water bypass outlet, now from the Thermostat housing.
Plan is going to be to change these o-rings/gasket and see if it stops the leak. Hopefully won't just move it to the next weak spot.
Radiator cap is new, and has been pressure release checked.
Overflow tank sucks in/out ok.
Haven't quite figured out what is going on.
 
Joined
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Baton Rouge, LA
I guess I'm suprised by the amount of pressure that's built up in the lower rad hose. If I squeeze the clamp open (not even to full release) it comes spraying out (after it's been running). That seems like a lot of pressure to me. But I might be underestimating the pressure in the cooling system.

I'm going to get some new constant tension clamps somewhere and update.
 
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Sep 17, 2003
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Sunnyvale, CA
 
 
 
I assume you put the correct clamps in the correct places - they are different diameters.

Also, did you use OEM hoses or aftermarket, I've seen small ID differences between OEM and aftermarket.

And, yes, it's a pressurized system and the lower hoses are at the low point and will spray if you release the clamp pressure, especially with engine hot - that's why there's always warnings about not releasing the radiator cap unless you want a potential steam cleaning...

cheers,
george.
 
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Baton Rouge, LA
I checked this morning and did put the correct hose clamps in the correct spot.

I think you are on the money with the Gates hose being a smaller OD. I picked up some constant tension clamps and am now good to go. Looks like I underestimated the pressure in that lower rad hose. I'm more than familiar with the pressure on the rad cap.

Thanks for the help everyone!
 

richardlillard1

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Mar 15, 2014
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I checked this morning and did put the correct hose clamps in the correct spot.

I think you are on the money with the Gates hose being a smaller OD. I picked up some constant tension clamps and am now good to go. Looks like I underestimated the pressure in that lower rad hose. I'm more than familiar with the pressure on the rad cap.

Thanks for the help everyone!
Sounds like You put the wrong clamps in the wrong places. We’ve put those Gates hoses on several 80s retaining the factory clamps and never had an issue. That said, there is a spring clamp and a worm clamp on my lower hose because I swapped them on that hose by mistake. That or, as rare as it is, I’ve seen a couple of the Toyota spring clamps fail. Usually from poor handling of them.

Either way, sounds like you’ve got it sorted out.
 

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