Confirm My Mad Scientist Idea!

[YukonRog]

So, as some of you know from my posts I am having my '05 Yukon's transmission replaced. I decided to replace the radiator, cooler, and all three lines due to contamination (metal) in the entire system. I'm saving myself some money by doing it myself. So before it goes to the shop, my idea is to bleed the new radiator by running the engine to operating temp. I've disconnected the output and return lines to the transmission and connected them together in a loop with a rubber hose. As far as I know the only thing turning in the transmission will be the torgue converter and pump. Not putting it in any gear. Am I correct in my thinking?

 

[Mudsport96]

May have some input shaft drag and rotation. Im not talking full engine rpm, but you will have something i THINK. Maybe someone who knows for sure will post.

 

[rockola1971]

Im bored and going to install square wooden tires on my Denali, Tie 100ft ropes (40 of them) to cinder block to drag behind the Denali and fill my front seat with concrete....to see how fast I can go. OP...you are overthinking it and making shi^ more difficult than it really is and likely going to burn your pump and/or converter up doing it.

 

[Bill 1960]

How’s he going to damage it running it in park? There’s no heat load. Connecting the two trans lines together returns the fluid exactly as if it were running through the radiator cooler. It’s just returning to the pan at the same temperature it left. Which won’t be hot, from a cold start and left in Park.

And in any case, it’s the old trans anyway if I understand the OP. He just wants to get his new engine cooling system bled before the vehicle goes to the trans shop.

 

[HD_LS]

So, as some of you know from my posts I am having my '05 Yukon's transmission replaced. I decided to replace the radiator, cooler, and all three lines due to contamination (metal) in the entire system. I'm saving myself some money by doing it myself. So before it goes to the shop, my idea is to bleed the new radiator by running the engine to operating temp. I've disconnected the output and return lines to the transmission and connected them together in a loop with a rubber hose. As far as I know the only thing turning in the transmission will be the torgue converter and pump. Not putting it in any gear. Am I correct in my thinking?

It should work well, assuming the transmission handles idling in park well, in it's present condition. Make sure your rubber hose loop is securely clamped on.

 

[rockola1971]

How’s he going to damage it running it in park? There’s no heat load. Connecting the two trans lines together returns the fluid exactly as if it were running through the radiator cooler. It’s just returning to the pan at the same temperature it left. Which won’t be hot, from a cold start and left in Park.

And in any case, it’s the old trans anyway if I understand the OP. He just wants to get his new engine cooling system bled before the vehicle goes to the trans shop.

Well in the case of using the old trans, no problem. But it could burn it up all the way, how you say, in park? That fluid is flowing in the torque converter because its spinning at engine rpm and the tranny pump is of course turning. That is a heat load. A tremendous heat load when there is absolutely zero cooling of the fluid and no air running underneath the vehicle. Thats how. And its a needless process. Have you ever heard of someone going to such extremes to change a darn radiator? Thats because its not needed.

Having problems bleeding cooling system? Park the vehicle uphill with front of vehicle facing to the upside. Let engine idle with radiator/fill tank cap off and run to operating temp. Add coolant as system bleeds.

 

[Bill 1960]

Well in the case of using the old trans, no problem. But it could burn it up all the way, how you say, in park? That fluid is flowing in the torque converter because its spinning at engine rpm and the tranny pump is of course turning. That is a heat load. A tremendous heat load when there is absolutely zero cooling of the fluid and no air running underneath the vehicle. Thats how. And its a needless process. Have you ever heard of someone going to such extremes to change a darn radiator? Thats because its not needed.

Having problems bleeding cooling system? Park the vehicle uphill with front of vehicle facing to the upside. Let engine idle with radiator/fill tank cap off and run to operating temp. Add coolant as system bleeds.

I’m not interested in getting into a ******* match on the internet, but you seem to believe a TC spinning freely generates a lot of heat and that’s simply not the case. They get hot when the input and output are at different speeds and high speed/low torque input is converted to low speed/high torque. As in stopped at a traffic light in gear or propelling the vehicle with the TCC unlocked.

In neutral, the input and output are at the same speed; there’s no fluid shear, and no heat. A trans in park has the clutches in neutral.

The load on the trans pump in neutral/park is minimal. It’s not doing any work and there’s no way it’s going to generate enough heat to raise the thermal mass of the trans to a critical temperature.

It may not be practical for the OP to park uphill with a non functional tranny as you suggest. Or not, I’m not saying that’s a bad idea.

In any case, I’ve said my piece, carry on. I’ll have no further contributions to this thread.

 

[George B]

All this argument over protecting a transmission that is getting replaced soon after the cooling system work is done.

 

[Mudsport96]

Well in the case of using the old trans, no problem. But it could burn it up all the way, how you say, in park? That fluid is flowing in the torque converter because its spinning at engine rpm and the tranny pump is of course turning. That is a heat load. A tremendous heat load when there is absolutely zero cooling of the fluid and no air running underneath the vehicle. Thats how. And its a needless process. Have you ever heard of someone going to such extremes to change a darn radiator? Thats because its not needed.

Having problems bleeding cooling system? Park the vehicle uphill with front of vehicle facing to the upside. Let engine idle with radiator/fill tank cap off and run to operating temp. Add coolant as system bleeds.

Not to be that guy, but ive driven a couple hundred miles ( short trips 20ish miles at a time) with the lines looped before. Granted it was a th400, but if you arent hot rodding or towing ot will be okay for a short time.

 

[YukonRog]

OP here. Wow, didn't expect all that. rockola 1971, can you pass whatever you're smokin over here? LOL! Square tires, ropes, cement, what the? You say I shouldn't run the engine to temp in order to fill the cooling system, then say I should run it. But park it uphill? It's not getting put in gear because it's throwing metal brother. You realize in a normal OE system the transmission fluid is cold to start and then warmed up by the radiator and then cooled to "operating temp" by the cooler right? By bypassing the radiator and cooler it didn't heat up. I ran it up to 210⁰ and the transmission lines and rubber hose making the loop were cool to touch. And I was able to fill the new radiator and the rest of the system with the T Stat open. Then I changed the engine's oil and filter too. Overthink it? Hardly. Needed to replace the radiator and didn't want to pay someone else to do that. Easy job. Puff, puff, pass...