hst oil cooler ?

glmf · Feb 13, 2011

My 4yr old ck20hst had the oil cooler fail on startup a week back. Bought a new one and was back in business shortly thanks to a well stocked dealer down the road. But had a question for the experts. When I start the tractor I always let the clutch lever up right after startup. The clutch pedal has a hold down catch on it. I wonder if it would be better to let the tractor run for a few minutes then release the clutch pedal as it doesn't circulate oil through the cooler with the clutch pedal down? Don't want this 150 dollar cooler failing again so trying to do what I can. Any thoughts would be appreciated

Coyote machine · Feb 13, 2011

Could you describe what you think caused the failure?
If I'm understanding what you're saying happens with the oil flow, it flows through the cooler when the clutch is engaged,(pedal released to up position), and stops flow when disengaged, (pedal down).
If you put the tractor in neutral and let the pedal up will that allow the flow to continue?

glmf · Feb 13, 2011

Yes, your description is correct. Except there is no neutral, just a low and high range. But even with clutch pedal down, loader and 3pt hydraulics work so there is oil flow, just not through the HST cooler, and both the loader and HST are a common sump. So I am assuming letting the tractor run for a few minutes on initial cold start with the clutch pedal down, then letting it up slowly may lessen the impact on the HST cooler, although the oil in the cooler loop will have to move before it takes any oil from the sump. Just trying to not blow another cooler. I am also guessing full synthetic oil may help as it has better low temp flow??

VictorW · Feb 13, 2011

The oil coolers just seem to a little on the thin side. I had the original one leak under warranty on my CK30hst, replaced it and then that one sprang a leak. I replaced the cooler again but did the rubber mounting and haven't had a problem in about 150 hours. I hold my clutch in after start up just about 10-15 seconds or so until the engine sounds like it's smoothed out. When you let the clutch up you can hear the extra load put on the engine. The oils recommended in my manual are a 10w-30 weight. I've seen synthetic Amsoil that's a 5w-40 weight, supposed to be for extended change intervals but it's around $150/5 gal. I wouldn't think that a difference of 5w would keep the cooler from blowing due to thick oil if that's what you think happened. My cooler leaks seemed to be from vibration and the rubber mounting has seemed to help.

Coyote machine · Feb 13, 2011

I remember a few threads about oil cooler failure issues and the need to suspend the cooler from vibration with some sort of dampening mechanism like adding rubber grommets.
I'm still unclear why the OP's cooler failed?

Amsoil is also a synthetic, not a dyno oil, so it will perform differently. It is unlikely that an oil will solve any poorly designed cooler issues- if that is what the actual failure cause/ effect is that renders the cooler useless in a short time frame. Is there a recommendation by Kioti for what to do with the pedal when warming up?

glmf · Feb 13, 2011

When I bought the new cooler, the dealer asked if I had the rubber hoses to the cooler. The original style had all steel lines right up to the cooler. New style includes couplers and short rubber flex hoses to isolate the cooler from vibration. My tractor has had the rubber lines since day one.
I believe the cooler is border line when temps are low and fluid is really thick causing pressure spikes til the oil reaches normal temps. This is why the cooler failed on startup on a cold day(zero or so degrees). It has lasted four years though so it has handled quite a few cold starts.
My only thought on synthetic oil is that is doesn't thicken as badly as dino and may have less pressure climb on cold starts.
My dealer also stated he keeps two of these coolers in stock and has seen this exact thing "quite a few time before".

Coyote machine · Feb 13, 2011

glmf said:
When I bought the new cooler, the dealer asked if I had the rubber hoses to the cooler. The original style had all steel lines right up to the cooler. New style includes couplers and short rubber flex hoses to isolate the cooler from vibration. My tractor has had the rubber lines since day one.
I believe the cooler is border line when temps are low and fluid is really thick causing pressure spikes til the oil reaches normal temps. This is why the cooler failed on startup on a cold day(zero or so degrees). It has lasted four years though so it has handled quite a few cold starts.
My only thought on synthetic oil is that is doesn't thicken as badly as dino and may have less pressure climb on cold starts.
My dealer also stated he keeps two of these coolers in stock and has seen this exact thing "quite a few time before".

I agree with the red ink section above. Synthetic is going to flow more easily- I've experienced it on my own vehicles here in VT, when using Slick 50 years ago on a couple of my vehicles. Nothing like adding Teflon to the oil to make it slick!
More flow equates to less pressure buildup, and less chance of something getting blown out.

mrutkaus · Feb 14, 2011

I would make the mounting flexible by installing the rubber grommets in front of and back of the mounting screws; see bottom of this page:

http://www.tractorbynet.com/forums/kioti-owning-operating/146288-pics-hst-oil-coolers-ck35s-3.html

Mike