New Mopar Radiator Installed, Engine Not Warming Quickly

[freedom_in_4low]

So, tell me how to fix this problem and make my life far less miserable. Flush, clean water coming out, thermostat is pulled so we can fast cycle it. Do one last fill, circulate and drain with distilled. Then we go back in with coolant, system is new MOPAR thermostat, new pump, radiator, etc.

Start it, watch for any coolant level to drop with the cap off so we can top it off if need be. Right about the time the dash reads a bit under 210, it explodes 2 quarts of expensive coolant out, the fan sprays it fucking everywhere. Now coolant is low, haul ass and top it back off.

As soon as the engine gets near the same temp as before, rinse and repeat. Blows coolant out the filler neck, fan sprays it everywhere, we top it off and it will keep doing that until we get tired of it or run out of coolant to add.

So you and Mr. 4 Low get your little heads together and tell me how to fix that problem.

Having thought about it a little more, I do remember doing the first warmup with the cap ON, and last time I did it I tried with the cap off and made a big mess as you described. The downside of cap-on of course is you can't really see what's going on, so you just have to trust the system to do what it's supposed to (push the air out into the reservoir when it gets hot and suck coolant back in when it cools), and check on it through a couple of warm-cool cycles, which isn't really that conducive to a situation where you're trying to get vehicles in and out on a schedule.

I might spend more time on the front end as well - I've experimented with different ways, like fill slowly until the radiator is full, squeeze the upper radiator hose to get any air out, put more in the radiator when the level drops, and repeat until I can't make it drop anymore. I've done things like filling it to just below the level of the thermostat, before actually installing the thermostat and housing, and then filling the rest of the way, which may or may not fit into your sequence of operations. I do this once every couple of years and my LJ (which hasn't even seen 1,000 miles yet in 2023) so I can afford to be slower about it.

 

[mrblaine]

Having thought about it a little more, I do remember doing the first warmup with the cap ON, and last time I did it I tried with the cap off and made a big mess as you described. The downside of cap-on of course is you can't really see what's going on, so you just have to trust the system to do what it's supposed to (push the air out into the reservoir when it gets hot and suck coolant back in when it cools), and check on it through a couple of warm-cool cycles, which isn't really that conducive to a situation where you're trying to get vehicles in and out on a schedule.

I might spend more time on the front end as well - I've experimented with different ways, like fill slowly until the radiator is full, squeeze the upper radiator hose to get any air out, put more in the radiator when the level drops, and repeat until I can't make it drop anymore. I've done things like filling it to just below the level of the thermostat, before actually installing the thermostat and housing, and then filling the rest of the way, which may or may not fit into your sequence of operations. I do this once every couple of years and my LJ (which hasn't even seen 1,000 miles yet in 2023) so I can afford to be slower about it.

If you drill a 1/8" hole in the thermostat flange and put that straight up, every single bit of that bullshit goes completely away. Fill it, engine gets up to temp, thermostat opens, no big blow-out of coolant, no risk of circulating without enough coolant in the system due to an air lock, no problems, no issues and it has exactly zero to do with a schedule. It only has to do with not spraying an explosion of coolant all over the engine bay, being able to monitor what is happening, and not dealing with any bullshit whatsoever. Ya'll keep fucking with it, I'm gonna do what works every single time.

 

[freedom_in_4low]

If you drill a 1/8" hole in the thermostat flange and put that straight up, every single bit of that bullshit goes completely away. Fill it, engine gets up to temp, thermostat opens, no big blow-out of coolant, no risk of circulating without enough coolant in the system due to an air lock, no problems, no issues and it has exactly zero to do with a schedule. It only has to do with not spraying an explosion of coolant all over the engine bay, being able to monitor what is happening, and not dealing with any bullshit whatsoever. Ya'll keep fucking with it, I'm gonna do what works every single time.

I've got a mopar thermostat with a jiggle pin in my parts pile waiting for the cooling system refresh I'll be doing next week (new radiator, water pump, and fan clutch).

 

[mrblaine]

I've got a mopar thermostat with a jiggle pin in my parts pile waiting for the cooling system refresh I'll be doing next week (new radiator, water pump, and fan clutch).

The jiggle pin doesn't work. The only one that actually works that you don't have to drill is the stainless ball in the crimped ends tube. That one is NLA.

 

[Actormike]

The thermostat was stuck open
Seems that when the radiator cracked it must have got stuck open from the fail safe tabs. Got a mopar this time which is made by the same company as the Napa one but not fail safe.

 

[freedom_in_4low]

The jiggle pin doesn't work. The only one that actually works that you don't have to drill is the stainless ball in the crimped ends tube. That one is NLA.

Looking at it, makes perfect sense that it doesn't work. It's shaped to work like a check valve and only allows flow in the opposite direction.

I can imagine it working on an engine where the stat lays flat so gravity pulls the pin down into the open position when filling/bleeding, and then pressure from the water pump would close it in operation. Maybe the jiggle pin was just an extra from parts-bin engineering from an engine where it actually worked.

But not trying to out-engineer anybody by any means.

 

[Link]

Pressure in a cooling system is from the coolant heating up and expanding. The water pump only moves the coolant. It doesn't pressurize it. The cooling system doesn't NEED pressure to provide cooling. Pressurizing the cooling system is to raise the boiling point. If you have a cooling system with a non working radiator cap, if it's not hot out, you'll never even notice any issues. Lack of pressure becomes an issue when it gets hot outside.

Vacuum fill it and you'll never worry about holes or jiggle pins in the thermostat. 100% fill fast every time.

 

[freedom_in_4low]

Pressure in a cooling system is from the coolant heating up and expanding. The water pump only moves the coolant. It doesn't pressurize it. The cooling system doesn't NEED pressure to provide cooling. Pressurizing the cooling system is to raise the boiling point. If you have a cooling system with a non working radiator cap, if it's not hot out, you'll never even notice any issues. Lack of pressure becomes an issue when it gets hot outside.

Vacuum fill it and you'll never worry about holes or jiggle pins in the thermostat. 100% fill fast every time.

If you're responding to me, you're correct that the pump doesn't pressurized the system but by making the coolant flow it creates a pressure drop across the thermostat and pushes the jiggle pin closed.