RTV x1100c oil foaming

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dtreid

Active member
Just finished rebuilding the gear portion of the tranny on my x1100c from a failed bearing.

Put things back together and filled everything up with oil.

Started things up and there is a lot of aeration of the oil in the tank under the seat.

If I run in for a couple of minutes, turn it off and crack the hst filter I get some air bubbling out.

Have bled the air by loosening the filter multiple times but the oil is still aerated.

Any suggestions or is this normal after a full fluid empty and change? I've changed lots of hst filters and tank oil and can't say I've ever spent much time looking in the tank. I do know that oil with air in it does not lubricate well, so I don't want to run it before I get this figured.
 
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aurthuritis

Well-known member
Site Supporter
foaming oil is real bad for your hst. if you used super udt and oem filters i suggest that you disconnect the little cable that attaches to the engine throttle at the fuel pump then with the transmission in neutral and the engine at idle i would slowly cycle the peddle from zero to full in order to purge all of the air out of the system. it could take a few times of start cycle stop and allow the bubbles trapped to dissipate and repeat. this should be done with the engine at constant idle,never reving the engine.
 
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dtreid

Active member
I did use kubota filters and udt oil. I ran the hst at idle back and forth several times, but the bubbles persist
 
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aurthuritis

Well-known member
Site Supporter
good on the oil and filters. to make myself very clear---- you need to cycle the hst speed valve fully open with the transmission in neutral and engine idleing to purge the air. then let it set until the oil clears of bubbles and then repeat until the oil flows without bubbles.
 
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aurthuritis

Well-known member
Site Supporter
just depends. the idea is to circulate the oil as gently as you can to purge any air without mixing in any more air. keep the pressure low and the volume high. as the air bubbles work their way out of the oil there could be more air pockets form. this is why you need to let it set for a while and repeat. you will know if it is working by watching the reservoir. depends on how foamy the oil was in the beginning. was the previous oil sudt? could there have been a mixing of two different kind of oils???
 
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dtreid

Active member
The oil I drained out of it was fairly dark even though the tag on it said it only had 200hrs on the change. I'm wondering if there may be residual different oil in things. I had the tranny off and apart so the only old oil should have been in the power steering/box lift circuit. I'm going to change the oil in the tank again anyway.
 
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aurthuritis

Well-known member
Site Supporter
probably a good idea. there might be some conflicting additives between the two oils??? shouldn't need to change the oil in the gearbox unless it wasn't changed in the first place?? new oil and filters are cheaper than pumps and valves anyway.
 
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dtreid

Active member
Figured it out.....inlet pipe to the hydrostat below the filters wasn't sealing properly. Was sucking air it when it was running.
 
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