Coolant leak

[fastfred]

Yesterday I was in climb from Pennsylvania and I could smell hot rubber and the CHT was high but not in the red. Everything else was normal for an 85 degree day. I leveled off right away and it cooled down and the smell went away. I slowly climbed to 4000 where the air was cool and continued 1.5 hours home everything looked good.
I inspected it before putting it away and found anti freeze spread spit out on the belly and firewall. The resivoir was empty but the filler was almost full.
I can find no leaks . I wiped it down , refilled and fired it up to operating temp with no leaks . I will let it sit for awhile and check some more.
I figure I will start replacing hoses and clamps. Is there a thormostat anywhere?

I appreciate any advice.

Fred

[Dorsal]

FWIW I had the hose between the reserve tank and the engine split at the connection to the engine side.

[Dave S]

Fastfred,


One idea, (but not the only possibility by any means) : on liquid cooled engines belching out coolant can be the result of the coolant exceeding its boiling point for one reason or another.


One point to keep in mind, the CHT is not the same as the coolant temperature. The actual temp of the coolant could possibly be higher than the CHT.



You should be able to determine if a thermostat is installed in your kitfox - if one is there (most don't use a coolant thermostat) it would be in line in one of the two 1" hoses. I am sure you could confirm or rule that out easily.


The coolant itself - I think most people are using 50:50 ethylene glycol - often Dexcool which works well. If the coolant is diluted - it would boil at a lower temp. If it is Propylene glycol (Evans) it should be full strength - not diluted.


Pressure cap. If the pressure cap does not hold the specified pressure on the system, a defective cap normally will result in a lower boiling point of the coolant.


Then there is the radiator; which must be in good condition and not plugged up with bugs and junk from the outside or dirt/sediment on the inside.


Hoses - A defective or weak hose can collapse on the suction side reducing coolant flow - probably not a common cause of anything since the system pressure will normally ovepower any tendency to collapse.


Don't know; but, at least a couple thoughts.

[rv9ralph]

Here is another possibility. If you changed coolant recently, air in the system can cause coolant to go out the overflow. The system will want to suck in more coolant as it cools, which is normal, if the overflow bottle is empty, it will get more air back in. The air expands more than the coolant when hot.

Ralph

[Wheels]

I zoomed out of my field on a hot day, I pulled up to VX and held it for a full minute. Suddenly lots to steam in the cockpit, the bottle had split under the cap and leaked coolant down onto the hot manifold, oops.

[fastfred]

Here is another possibility. If you changed coolant recently, air in the system can cause coolant to go out the overflow. The system will want to suck in more coolant as it cools, which is normal, if the overflow bottle is empty, it will get more air back in. The air expands more than the coolant when hot.

Ralph
Is there another overflow that doesn't go back into the tank?
The only place I can find is where it might have blown past a clamp on the pump.

[fastfred]

[QUOTE=Dave S;74804]Fastfred,


One idea, (but not the only possibility by any means) : on liquid cooled engines belching out coolant can be the result of the coolant exceeding its boiling point for one reason or another.


One point to keep in mind, the CHT is not the same as the coolant temperature. The actual temp of the coolant could possibly be higher than the CHT.


Don't see any thermostat. What keeps it from overheating? How would you know if the cht not an iducator?
It appears it blew past a clamp.
How about the coolant pump do they go bad and what would it do?

[jiott]

What keeps it from overheating is a properly sized radiator and oil cooler. A thermostat only helps from overcooling. Most of us don't have an actual coolant temp readout, but if either the CHT or the oil temp gets close to the redline, you have a problem and need to figure out the cause. Most likely an airflow restriction thru the radiator/cooler, a partially clogged radiator/cooler, a kinked oil line, a collapsed radiator hose, low coolant/oil level. Its pretty rare for a coolant pump to completely fail; usually the seals go bad first and you will notice leakage and loss of coolant.

[fastfred]

Thanks Jim
I am trying to duplicate the climb and test it. I guess it was a combo of High heat , high RPM, high weight and most likely high density air.
I lost a quart of coolant but I can't see where it came from is my problem. I think the leaked stop once I leveled off into cool air? Otherwise I was diverting
I am going replace the hoses and clamps first. We are guessing they are original and I will clean out the radiator . How about that synthetic coolant rotax recommends? The radiator doesn't look that dirty but this is a new plane to me so who knows if it was ever cleaned out or how old the hoses are. I could smell a hot hose was the only thing that told me there was a problem.

[jiott]

The waterless coolant Kitfox used to recommend is now definitely NOT recommended by them. If that is what is in your system, it needs to be properly drained and cleaned out, and refilled with Dexcool 50/50 anti-freeze. You will find your temps will drop 10-20F.

[fastfred]

That 50/50 is what I put in last fall . One of our locals has the rotax repairman class and said they recommend the waterless . Not sure how long ago he took it.

[jiott]

He must have taken the class a year or more ago; Rotax has flipped on the Evans and now recommend against it.

[fastfred]

I am sure he took it a long while ago. Glad I spoke to you before I ordered it.
While I got you . How often do you change the plug wires? My left side recently started to drop 200 rpm in run up. Plugs have about 30 hours on them.

[jiott]

I have 600 hours on my original plug wires and don't plan to change them soon. Before I change plug wires I would try unscrewing the boots and clipping of about 1/4" of wire and reinstalling the boot. It often solves ignition problems.

You really should be continually monitoring the Rotax-Owner website and read the forum posts on a regular basis. Nearly all the questions you have asked have been discussed many times on the forum, including my suggestion of clipping the plug wires. Any Rotax owner doing his own maintenance should be reading that forum. That website also announces each new service bulletin as it comes out, like the one recommending against the Evans coolant. A Rotax repairman who doesn't keep up on service bulletins would be highly suspect in my opinion.

[fastfred]

[Yeah I have been lax on going to their site .I paid for it so I should lean to use it more.

Thanks

[jiott]

Most of the info available on the site is free, including the forum and all the service bulletins and engine manuals. The only thing you pay for are the how-to videos (some of them are free). I have been watching that site for 5 years and have learned a ton; plus you can ask a question and an expert will reply usually in less than a day.

[rv9ralph]

FastFred,
I'll try to explain, but first some background on my 912 setup. It is an early (91) install, there is not an expansion tank like on the newer 912s. I have a plastic overflow bottle connected to the filler neck to catch coolant overflow from the pressure cap.
The point I was trying to make, and it may not apply to newer installs, is that if there is air that has not been purged out of the system it will expand when hot and push coolant out into the overflow. When the system cools down it pulls coolant back into the system, replacing any air that was expelled. This is how auto systems work.
I had an experience when, after replacing my coolant, in order to get the engine up to temp for a ground run to check propeller pitch, I blocked a porting of the radiator. This did allow the engine to reach operating temperature sooner (it was a cold day). However, some coolant was purged (and overflowed my catch bottle) which I replaced because the system sucked the overflow bottle dry.
The odor is normal when this happens.
Hope this explains what I was referring to.
Ralph

[fastfred]

That sounds similar to what happened but how does it get out of the overflow bottle? Through that tiny hole?
What is the best way to purge the air out?
I am also not sure when the last time the radiator fins were cleaned out so I will try that also. It is suppose to be very hot here so I will get a chance to duplicate the climb last week.
Mine was built in 2004 but the set up sounds similar. Service log is not great for the last few years so I am guessing the hoses and clamps are original so I think I will replace them as insurance .

Thank you