Draining and filling a radiator while hot....

[gregk24]

I am planning on doing a drain and fill of the transmission and radiator on the Accord tomorrow. I have to drive to the dealer to get the parts so the car will be warmed up. I don't have any problem draining the trans while hot, but I know the radiator is under pressure. Is there a safe way to drain it when its hot/warm or do you have to wait until its cold. Is it safe to open the drain plug on the radiator to let some pressure out and then open the cap on top? If not, how long should I wait before opening it up. I mean the techs at the dealership have to do it when its hot, right? TIA!

Also: Tonight I took of the plastic shield underneath so I could access the transmission drain plug, is it safe to leave this shield off for a couple of drain and fills over the course of a couple months? or should I put it back on after each drain and fill. Its just a little bit of a pain thats why I ask.

 

[Dave Hess]

Wait till engine coolant is warm to drain.

I've drained Honda ATF right after a highway drive, use caution and gloves as ATF gets very hot.
Leave shield off for a week so you can do 2 drain/refills.

No need to put car on ramps, just turn wheel all the way to one side and drain plug is easily removed. Use a large cardboard to catch any ATF that might drip.

 

[Brad_C]

Just let the car cool off while you are doing the trans drop. As long as everything is below boiling point, vent the gas out of the cap slowly and you are good to go.

 

[01rangerxl]

I'd be mostly worried about introducing cold coolant to hot parts. It doesn't need to be dead cold, but let it sit until you can touch the tanks (for more than a few seconds). Can you drive another car to the dealer?

 

[Garak]

I don't know what the rad cap and associated plumbing are like on your car, but there was a way I would do it on the old taxis when absolutely necessary. I'd turn the radiator cap to the first stop, while wearing gloves and holding a mountain of rags over the cap, gripping it in that fashion. That way, most of the coolant expelled would go directly to the expansion tank, thanks to using the first stop, and whatever escaped would go into a pile of rags, rather than my face, hands, or arms.

It's something I'd rather not do unless absolutely necessary. Unfortunately, with taxis, it sometimes was. If you can let the car sit and cool appropriately after picking up the parts, that would be my recommendation.

 

[The Critic]

I've done it many times - place the pan underneath the car, open the valve. Then go on top and loosen the radiator cap.

Refill once drained and hose down the engine bay -- it will make a mess.

Airlift/vacuum refill the system, then allow engine to run for about 45 min or until the fan comes on twice. Use a coolant funnel if you have one, otherwise, loosely install the cap. After the fan comes on twice, top off the rad and then close the cap. Top off reserve bottle to about 1/2" above the full mark.

In total you'll need about 6 quarts of Type 2. I usually do not bother changing until about 60k or 5 years.

 

[Brybo86]

There is a small stopcock under the radiator ..... reach in and twist it.. No need to remove the plastic cover it is directly below the radiator cap at the bottom of the radiator

 

[901Memphis]

I always waited about 10 minutes before draining and never really had an issue. Last time I did a lot of drain and fills in the same day I also had a big house fan blowing over the radiator in those ten minutes to help. It was hot enough to hurt the hand but not hot enough be over boiling.

 

[gregk24]

Originally Posted By: Brybo86
There is a small stopcock under the radiator ..... reach in and twist it.. No need to remove the plastic cover


I know, I removed the cover to access the transmission drain plug. Which leads me to ask again, is it safe to leave the cover off for a couple of drain and fills? Or is it there for more than MPG?

 

[RedOakRanch]

Set a box fan face down right on the engine/radiator, it will be cold to the touch in minutes.

 

[gregk24]

Originally Posted By: 901Memphis
I always waited about 10 minutes before draining and never really had an issue. Last time I did a lot of drain and fills in the same day I also had a big house fan blowing over the radiator in those ten minutes to help. It was hot enough to hurt the hand but not hot enough be over boiling.



I didn't think about that. I guess I could just leave the key turned to the "on" position and turn the A/C button on, this will keep the radiator fans blowing and should help cool it off more quickly.

 

[Kuato]

Originally Posted By: 01rangerxl
I'd be mostly worried about introducing cold coolant to hot parts. It doesn't need to be dead cold, but let it sit until you can touch the tanks (for more than a few seconds). Can you drive another car to the dealer?


In your place I would leave the hood open help cool it while you do the transmission job, have dinner then it should be good.

 

[The Critic]

Really though, what do you think the flat-rate mechanics do at the dealer? They can't leave a car to cool for 2-3 hours before doing a coolant drain/refill on something that was probably written-up as a "waiter."

 

[901Memphis]

Originally Posted By: gregk24
Originally Posted By: 901Memphis
I always waited about 10 minutes before draining and never really had an issue. Last time I did a lot of drain and fills in the same day I also had a big house fan blowing over the radiator in those ten minutes to help. It was hot enough to hurt the hand but not hot enough be over boiling.



I didn't think about that. I guess I could just leave the key turned to the "on" position and turn the A/C button on, this will keep the radiator fans blowing and should help cool it off more quickly.



Yes but be prepared to charge the battery afterwards. I wouldn't want that kind of drain on my battery without charging later.

 

[Dave Hess]

Originally Posted By: The Critic
Really though, what do you think the flat-rate mechanics do at the dealer? They can't leave a car to cool for 2-3 hours before doing a coolant drain/refill on something that was probably written-up as a "waiter."



That's why a lot of Flat Rate mechanics do [censored] quality work.

They are in a rush to beat the clock so they can make a living, if they can't meet book time .... they are working for free.
Flat Rate was designed to make the business Max profit while mechanic makes peanuts.

 

[cptbarkey]

you are over thinking it. wait 10 minutes, drain. refill immediately, move along with life. its not an infant that only likes warm milk so for petes sake dont put the antifreeze in the microwave.

 

[01rangerxl]

Originally Posted By: Kuato
Originally Posted By: 01rangerxl
I'd be mostly worried about introducing cold coolant to hot parts. It doesn't need to be dead cold, but let it sit until you can touch the tanks (for more than a few seconds). Can you drive another car to the dealer?


In your place I would leave the hood open help cool it while you do the transmission job, have dinner then it should be good.

Yep, just about any other task you do should provide enough cool down time. If it's not an emergency, then just do something else first. If you have to rush, just pick a different day. Things will probably work out better if you do.

As for what flat rate techs do...the car is going to sit regardless before they get around to it. They aren't draining coolant within 5 minutes of the car showing up. More like 20+ minutes in an ideal situation.

 

[HTSS_TR]

Originally Posted By: gregk24
I know, I removed the cover to access the transmission drain plug. Which leads me to ask again, is it safe to leave the cover off for a couple of drain and fills? Or is it there for more than MPG?

It's more than MPG, it prevent the rocks/sands spit out from the front tires damage engine's hose/pipes.

But some years ago many vehicles didn't have splash shield and they didn't suffer much damages.

When I change coolant in my S2000 I back up the car on the inclined driveway so that the front is lower, this way more coolant can drained from the engine.

When drain coolant you want to set heater to max without running the engine and fan, the heater valve will open to let coolant in heater core drain out, also open the air bleed valve on top of the engine, it will assist draining the coolant.

When you fill the radiator turn the car around so that the front is higher and you can fill coolant/water(with air bleed valve opened) into radiator to near maximum of the coolant system.

 

[gregk24]

Just an update...I was able to complete the coolant drain and fill as well as the ATF drain and fill without any issues. While doing the ATF drain and fill I let the cars fans run (with car off) for about 10 minutes then I shut them off. By the time I got around to draining the coolant which was no more than 20 minutes the coolant was cool enough and not under excessive pressure so it was as simple as it has ever been. I went ahead and put the cover back on, I figured I would wait until my next OCI is due before doing another ATF drain and fill which wont be for a couple months. Better to have the cover on than off for that extended period of time.

 

[dishdude]

So you can turn your ignition to run with the engine off, switch the A/C on and the radiator fan will run?