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Old 01-13-2015, 07:20 PM
lpeeds lpeeds is offline
Join Date: Jan 2012
Location: Shelby, NC
Posts: 26
Default Leaking radiator hose.

I had a problem with the hose from the water pump to the radiator leaking. Went thru several of the worm clamps before finding some heavy duty clamps at NAPA that did the job.
Paul Eeds
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Old 01-13-2015, 07:27 PM
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LifeofReiley LifeofReiley is offline
Join Date: Jan 2005
Location: Round Rock, TX
Posts: 3,776

We always called these Cold Water leaks and Silicone coolant hose seems to be the most difficult to get to quit leaking. The wider HD worm clamps will usually solve the problem.
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Old 01-13-2015, 10:23 PM
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Rick_A Rick_A is offline
Join Date: Oct 2005
Location: Highland Village, TX
Posts: 1,382
Default Spring Clamps recommended

Originally Posted by lpeeds View Post
.... Went thru several of the worm clamps before finding some heavy duty clamps at NAPA that did the job.
I just got back from iRMT class at Lockwood. We discussed hose clamps and we were told that Rotax has a good reason for using the spring clamps. The spring clamps allow for expansion without deforming the hoses. Worm clamps, on the other hand, tend to deform the hoses, especially because most people over tighten clamps.

It's easy to get in a vicious cycle of tightening the clamps to stop the leak - deforming the hose by over tightening and having the leak re-appear then tightening some more, etc.

BTW. We also used a cable operated hose clamp plier. The make installation/removal of spring clamps super easy and you don't have to worry about damaging the clamp.You can find them at auto parts stores for under $25.
Rick Aronow,
Flying 7A Slider;
RV-12 (ELSA, Dual G3X), SOLD
Highland Village,TX
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Old 01-30-2015, 08:06 AM
DQC DQC is offline
Join Date: Nov 2011
Location: Payson, AZ
Posts: 7
Default coolant leak at overflow bottle

I had a similar problem. On pre-flight, found coolant on hangar floor below cowling, under passenger floor mats, and coolant spots all around firewall. Coolant overflow bottle almost empty. Bottle OK, cap breather hole OK. Diagnosis: leakage during previous day's flight at slip-on hose connection to bottle. Hose elasticity probably compromised, especially at bottle connection tube 'bulb'. I cut off 3/4" at hose end, reattached, but added hose clamp. Hose rubber at end of useful life? TT @ 230hours, Engine installed June, 2010.
Don Payson AZ
RV-12 D180 AP74
C172K Skyhawk
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Old 06-25-2016, 02:37 PM
PilotBrent PilotBrent is offline
Join Date: Dec 2011
Location: Hackettstown, NJ
Posts: 421
Default Hose to overflow bottle failed today

After a few hours of Young Eagle flights today, and about to put my -12 back in the hanger, notice a puddle forming of Dexcool coolant on the taxiway. The hose attached to the reservoir for the coolant had failed. Small crack in the rubber and the hose apparently fell off. Lost about 2/3 of the coolant in the overflow bottle but coolant level in the system itself unaffected. Rest of hose looked fine - cut off about 1/2" and reinstalled. Probably discovered it just after it happened as a lot of the coolant was still dripping through the engine area.

Brent Connelly
Hackettstown, NJ
RV-12, N913BC

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Old 06-25-2016, 03:50 PM
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DaleB DaleB is offline
Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 1,825

After doing my condition inspection and hose replacement, I refilled my cooling system with fresh Dexcool. Filled the reservoir up just a hair below the MAX line. On the first test flight I thought I caught a whiff of coolant while on the ground, but everything seemed fine. After the engine cooled down, I noticed the coolant level was down about 3/4 inch. Looked for a leak, found nothing, topped it back up. Same thing on the next flight. I finally figured out maybe the MAX line was a little above the MAX for my plane. So, stopped topping it off and it hasn't lost any since then.

Kind of like putting 8 quarts of oil in a Lycoming. Dipstick says it's full, but the engine will usually just blow a quart overboard and find its own "full".
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Old 06-25-2016, 03:53 PM
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tomkk tomkk is online now
Join Date: Apr 2014
Location: Port Orange, Fl
Posts: 714

Yeah, I had exactly the same experience ...
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Old 06-25-2016, 03:56 PM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 4,214

Originally Posted by LifeofReiley View Post
We always called these Cold Water leaks and Silicone coolant hose seems to be the most difficult to get to quit leaking. The wider HD worm clamps will usually solve the problem.

Hose materials creep under load, and ordinary hose clamps have a constant diameter, regardless of the force. Once the temp goes up the expansion of the aluminum tube, and accelerated creep of the hose material, the fixed diameter of the typical clamp is no longer "tight" when it cools back down. The spring-type hose clamp is the only solution for this. This also applies to turbocharger hoses, so you will notice these on heavy duty applications. These will solve the cycle of hose leaks.

For the finding the leaks ( BMW is a super PITA about leaks) I use a tee in a small hose (1/4" ID), and with a cheap air pressure regulator, gage and valve, use this to pressurize the system. Just be sure not to exceed the cap rating. Then I got some dye from O'Reilly's for the coolant and use a black light to locate the leak source. It will stand out like a sore thumb. ZEP orange cleaner will remove the dye for continued monitoring. You can use a small pressure tank as this won't take much air supply. Heck, your garden sprayer will generate enough pressure. ($7)

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Last edited by BillL : 06-25-2016 at 04:35 PM.
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Old 06-26-2016, 12:06 AM
Sink Sink is offline
Join Date: Apr 2015
Location: Altha, FL.
Posts: 114

Coolant hoses can ooze or leak when exposed to heating and cooling cycles and especially in cold weather it may shrink a tad and the clamps being a different material don't keep up. The rubber will compress from a clamp over about 25 hrs. During the Rotax first 25 hr. warranty inspection or after a hose change these clamps should all have a wrench put on them to check for tightness.
As far as a wormdrive clamp I personally don't like the serrated type with the openings. These can be over tightened and slip and they cut into the hose.
Many prefer the Wurth wormdrive style clamp. It has raised ridges and will not cut into the hose and usually won't slip the notches like a serrated open grooved type will unless you severely over tighten them. It's a better choice over the garden hose variety type.
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Old 06-26-2016, 10:22 AM
philrisl philrisl is offline
Join Date: Apr 2014
Location: Deltona, FL
Posts: 13

In answer to an old question in this subject, the radiator pressure tester from Harbor Freight Aviation Supply has an adapter that works on the Rotax.
I also found the spring loaded worm clamps work great at the radiator hoses. It helps that they completely wrap around the hose under the worm screw.
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