Kubota L275 Radiator Empty/Flush Using Petcocks

Keith_ · Oct 17, 2022

There are two petcocks for draining the radiator but they have tiny holes that will take a long time. Is this the intended method? I think just pulling off the lower hose would be better/faster. The second petcock was as a recent discovery and why the radiator would not accept the intended amount of coolant, so I have to do it all over again since what I put in will now be diluted with water. This time I plan on using vinegar to remove rust/scale as recommended in other threads before refilling. The second petcock must be able to drain/release the other 3 quarts of coolant. Just looking for comments from others who have had similar experiences regarding the petcocks and the dribble drain method that might take hours vs minutes removing the hose.

jddrawbar · Oct 17, 2022

Keith, I have a L275 and it doesn't have the petcocks that you described. I have the petcock
on the bottom of the radiator & it drains just fine.

Steve@Advance · Oct 17, 2022

Block drain petcocks are usually clogged with sediment. You can take the petcock out and clean out the
sediment with a stiff wire.

Best way to flush is to remove the thermostat or bypass hose so water will free flow through the system with
the engine running. Hang the garden hose in the radiator, open all the drains, start the engine and run it
up to speed with clean water going in and the dirty water and vinegar being flushed out. When it runs clear
water, usually about 15 minutes of flushing, turn everything off, replace the thermostat or hose, let it
drain, and refill with 50-50. Or use straight antifreeze and distilled water.

But, if it was full of rust, expect to have to repeat soon as there will still be rust in the bottom of the
block. It may or may not stay settled, depending on how bad it got.

Keith_ · Oct 17, 2022

(quoted from post at 08:06:21 10/17/22) Keith, I have a L275 and it doesn't have the petcocks that you described. I have the petcock
on the bottom of the radiator & it drains just fine.

Interesting. I have not been out to look at my tractor yet but only found the second petcock in the manual. I'm not sure how else the water jacket gets fully drained. I'll take a peek at it today to see if it really exists.

Keith_ · Oct 17, 2022

Guessing "all drains" being petcocks only? So once system is full of fluid water/vinegar, the garden hose would only be a trickle since petcock holes are so small to drain. The manual says this is supposed to be flushed and filled yearly. Is that typical of all tractors? Other engines do not seem to have this requirement.

Steve@Advance · Oct 17, 2022

The garden hose can be overflowing the radiator along with coming out the drains.

The object is to flow in enough fresh water to eventually dilute and replace what's in there. You want to
get out all the rusty and vinegar mixed water, then give it time for the water to drain out completely. The
drain cocks will flow a good amount if you clean them out, sometimes a blast of air will clear them if you
can get to them.

Once you get it refilled with premium quality antifreeze (the owners manual should give the spec) and
distilled water it will be good for 5 years or so.

When they build these tractors, they go all over the world, some go to 3rd world countries that may not have
access to good antifreeze and distilled water. They want to err on the side of caution.

Keith_ · Oct 17, 2022

Thank you, makes very good sense, especially on longevity with proper flush/fill.

(quoted from post at 15:24:54 10/17/22) The garden hose can be overflowing the radiator along with coming out the drains.

The object is to flow in enough fresh water to eventually dilute and replace what's in there. You want to
get out all the rusty and vinegar mixed water, then give it time for the water to drain out completely. The
drain cocks will flow a good amount if you clean them out, sometimes a blast of air will clear them if you
can get to them.

Once you get it refilled with premium quality antifreeze (the owners manual should give the spec) and
distilled water it will be good for 5 years or so.

When they build these tractors, they go all over the world, some go to 3rd world countries that may not have
access to good antifreeze and distilled water. They want to err on the side of caution.

caterpillar guy · Oct 17, 2022

Some of those drains have a short little spout on them and mud daubers will plug them with nest. Poke it out and slip a piece of hose on it then it is not such a mess. And you could just let it drain into a container big enough to hold it all drain over night. then do your flush and refill. Though I would wait till spring and drain flush with water refill and run for the summer or a month or 2 to get the rust slop loose and flushed out then fill after it has had a chance to be fully cleaned out.

Keith_ · Oct 24, 2022

Just a follow up on getting this all completed. I removed all the hoses, thermostat, and thermostat housing and flushed everything directly with a garden hose all while having both petcocks open. So a bit more than required but figured it would be worth it. After reassembly and refilling it still did not seem to take the 7 quarts the specs indicated, so that is still a mystery. That was even after letting the tractor run and warm up so that the thermostat would open. Level never changed. I mowed small area to further warm the tractor up, let cool off and recheck but level still had not changed. The next time I do this I will measure the output volume to the last drop before refilling. It sure seems like it only took between 4 and 5 quarts, so in my opinion that's quite a difference. The thermostat must have opened though since the top hose was hot. It was replaced the last time I did all of this just in case and since it was inexpensive. I know I can test the thermostat outside of the tractor as well and may do that next time too "just for fun" ;-)

Kubota L275 Radiator Empty/Flush Using Petcocks

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