Pressure build-up in radiator. (1 Viewer)

[Ted44]

1996 FZJ80
Earlier this year the top radiator tank exploded. It sounded like a shotgun. I replaced the radiator and hoses. While on the trail recently I noticed coolant dripping. All hose clamps are tight. Recent test drives have not duplicated the problem, but I still wonder about the exploding tank and the pressure build-up. Maybe the tank was old and faulty, but...

What could cause a pressure build-up like this?

 

[BILT4ME]

The cooling system pressurizes while you operate it. This system is a 13 PSI I believe, so it will pressurize to 13 PSI before the cap relieves and allows overflow into the coolant overflow tank. A it cools, it draws coolant back into the system.

It is not uncommon for a clamp to be loose and only show up during hot pressurized condition. Once it has been tightened, the problem SHOULD be gone. If it repeats, then replace the hose and the clamps again.

I, too, had a radiator explode. I have since gone over my system and changed most of the things I need. I know there are a few I need to do, but I will do that at my next coolant flush.

 

[10mm Nut]

Testing the radiator cap is easy if you have access to the tool (rental at some parts stores). Just pump it up and see if/when the caps relieves pressure. Lacking the tool, replacing the cap with a high quality new one is cheap enough.

 

[bigredmachine]

I woud just replace the rad cap if you didn't when the rad was replaced, its cheep enough that theres no reason not to. could the coolant be leaking form somewhere else possibly

 

[Ted44]

The cooling system pressurizes while you operate it. This system is a 13 PSI I believe, so it will pressurize to 13 PSI before the cap relieves and allows overflow into the coolant overflow tank. A it cools, it draws coolant back into the system.

It is not uncommon for a clamp to be loose and only show up during hot pressurized condition. Once it has been tightened, the problem SHOULD be gone. If it repeats, then replace the hose and the clamps again.

I, too, had a radiator explode. I have since gone over my system and changed most of the things I need. I know there are a few I need to do, but I will do that at my next coolant flush.

Thanks for your reply.
My worry is there is a condition causing excess pressure.

 

[Ted44]

The cooling system pressurizes while you operate it. This system is a 13 PSI I believe, so it will pressurize to 13 PSI before the cap relieves and allows overflow into the coolant overflow tank. A it cools, it draws coolant back into the system.

It is not uncommon for a clamp to be loose and only show up during hot pressurized condition. Once it has been tightened, the problem SHOULD be gone. If it repeats, then replace the hose and the clamps again.

I, too, had a radiator explode. I have since gone over my system and changed most of the things I need. I know there are a few I need to do, but I will do that at my next coolant flush.

Thanks
I am worried about what causes the excess pressure. Is there something more serious lurking?

 

[BILT4ME]

Define excess pressure.

The only other thing that would pressurize above the radiator cap relief point is a bad radiator cap combined with a head gasket.

In my case, the radiator cap was gunked up and failed to open in a timely manner and the PO had shiity cogged belts on it. During a wide open throttle run, I backed out of it to shift, the sudden rpm caused the belts to snap and wrap around the water pump, stopping the WP. Temp spiked, the cap didn't relieve, and the radiator blew, as if I'd blown a tire.

The cooling system was gunked up due to mixing red and green coolant and general lack of maintenance.

So, service your cooling system, use a new TOYOTA radiator cap, and do your maintenance.

Don't search for a head gasket if the symptoms are not there.

 

[10mm Nut]

It's just thermal expansion. When a volume of water is heated, it expands. Since it's contained inside of a closed system, the volume cannot change, therefore the pressure must increase. That is the source of the pressure. The added pressure is a benefit since it also raises the boiling point of the coolant. That is the reason that the cap on a cooling system is rated to hold a certain amount of pressure. Once the pressure rises to the level of the cap's rating, it opens and allows coolant to spill into the surge tank. Then when the engine is shut off and the coolant cools and contracts, a vacuum is formed which draws that coolant out of the surge tank and back into the system.

This is all very typical of all vehicles since roughly the late 1960s.

The problem is that a lot of people underestimate the importance of the radiator cap and it becomes an afterthought in their maintenance regime.

 

[inkpot]

Thanks for your reply.
My worry is there is a condition causing excess pressure.

A functioning radiator cap SHOULD release anything over 13#. Most common cause for enuff pressure to blow up the tank is headgasket failure.

 

[flintknapper]

It can certainly happen. Plastic radiator top started leaking on my 100 series but spit on my 80 series.

Not mine below...but representative of what can happen.