I began having sudden cooling issues after 850 hours of trouble free operation. Radiator is flowing good,After the CHT temp rose to 260F I shut the engine down. I realize now the overflow bottle had very little coolant in it after fluid had gotten this hot. I have the Westach sending unit for temp indication on my quad gauge. I am wondering if I should start with a new indicator,as the one installed now is many years and hours old. The lines are all free and clear. I need information on how to best check the water pump to see if it is delivering coolant.I disconnected the hose from the radiator to water pump and filled water to to the top of pipe with it vertical. I turned the starter over for about 3 seconds and the pump had not sucked any fluid from the pipe. I would like to know if there are ways to check the water pump.  Also all other engine indications were normal. 

  • Re: Water pump

    by » 3 months ago

    Can you not just remove the water pump inlet hose elbow and make sure that the impeller is still attached and not just spinning? If it is spinning, you will have to investigate further to find out where the disconnect lies.

  • Re: Water pump

    by » 3 months ago

    "...............sudden cooling issues ................"

    A "sudden" rise in temperature is usually caused by rapid loss of coolant, restriction of air or coolant flow.

    Check for:

    # Collapsing coolant hose.

    # Loose component in engine compartment, intermittently restricting air flow in/out of cowling.

    # Correctly functioning radiator cap.

    # Temperature gauge or sender/sensor malfunction.

    "After the CHT temp rose to 260F I shut the engine down."

    I am intrigued - how did you continue the flight?

    In general you should not "shut down" a hot engine - you should keep the engine running at reduced power to maintain coolant/oil flow and enter a shallow descent, to maintain good air flow - land at the earliest opportunity to assess problem.

    ".......overflow bottle had very little coolant in it after fluid had gotten this hot."

    The overflow bottle is actually an expansion tank ie it allows for heated/expanding coolant to escape and on cooling, return to the cooling system. The fluid level should be part of your preflight checks. The cool fluid level, should be around 1/3  to 1/2 of the expansion tank - the level will rise when engine hot. There should be very little discernible change in the fluid level between service activity. Any change, from the usual level, should be cause for concern. 

    Note: fluid level, in the cooling system (under radiator cap) should be completely full at all times (no air gap). 

    127C (260F) is a high temperature but within Rotax maximum limits - this alone would not cause your expansion tank to empty ie there must be another factor.

    The "water" pump is, at best, a marginal performer - its job is to maintain a posative flow in one direction. If its connected & rotating with engine turn over it is likely to be working as designed ie nothing wrong.

    I would start by checking your temperature monitoring system - it may be giving false readings.

    At the same time - check the radiator cap is in good condition & meets the current Rotax part number.

    I assume you have replaced all rubber components at the Rotax recommended 5 year interval. This is also an opportunity to replace the coolant (Personally I do this at  2.5 years). Use quality concernatre at 50:50 mix with pure (not tap) water. 

  • Re: Water pump

    by » 3 months ago

    Thank you for the reply. I didn’t mention engine is 912s on a Kitfox I completed 22 years ago. Luckily the temp rise was on taxi to the runway. No previous problem. I agree with all you said. After talking with Lockwood tech support, I am sure ( hopefully) it is the radiator cap.I have never changed it since new. No pressure might also be why there was no extra coolant flow into the over flow bottle. I spent the day changing all coolant lines,I should have it completed tomorrow. I have a new radiator cap coming from Lockwood, and a new Westach sensor also.I should be able to post the results next week.

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