Coolant Drip

[hbertoni]

New coolant hoses were installed on my CT, as called for at the 5 year inspection.  Since then I have experienced considerable leakage on cold winter nights.  I have tighter the hose clamps several times, but still get some leakage in the winter.

 

Short of sleeping at the airport on the coldest night of the year and tightening the clamps at 4:00 AM, is there anyway to stop the drips?  

 

As a side issue, the overflow tank seems to be mounted too low on the firewall for the engine to draw back in the leaked coolant, so checking the level in the tank does not insure adequate coolant in the engine.

 

[Anticept]

Are you sure it's the hoses, or is it leaking around the threads of the fixtures? You can try buying new clamps, or put another clamp on for good measure.

 

As for the overflow tank: no matter what height it is mounted at, at least checking fluid level periodically is advised. If the relief cap leaks, it will spill out fluid, or be unable to draw any back in. That's why rotax recommends checking before each flight (which is honestly a little excessive unless you are going to fly over a large body of water or through mountains with no good landing sites). In addition, your leak is too slow to generate enough suction to draw from the tank. The overflow bottle's purpose is to absorb surges in coolant level due to vaporization in hot areas, not to act as a standby reservoir. That's what the overflow assembly (the splitter) on top of the engine is for.

 

As a side note: if your CHT reads higher than normal, checking coolant should be the first thing you do. A guy hosed a brand new engine that is now sitting at Lockwood as a training engine, because he ignored the CHT warning. The engine ran 3 straight hours through aggressive touch and goes and speedy flight with no coolant, and the owner went back the next day to do it again when he noticed it wasn't developing power. It warped the hell out of the heads and trashed the engine.

[Runtoeat]

Hbertoni, my friend had rubber changed on his CTLS and fought coolant leaks for some time after the change.  He tried to stop leaks by adding multiple clamps, repositioning the hoses on the metal pipes, etc.  Coudn't fix the leaking.  I believe he fixed this by installing different supplier coolant hoses with maybe a different compound for the rubber?  Recommend you call Dave at FD USA and see what he might suggest. 

[Roger Lee]

Coolant leaks usually come from a couple of sources. The first one happens when there are heating and cooling extremes like you get in snow country. The water pump seal is ceramic and coolant flows between the two halves as a lubricant. Some times you can get a tablespoon or two on the ground from the back of the engine out the weep hole in the bottom of the water pump.

This is normal, but this doesn't happen to everyone.

 

Another leak area is from people doing a hose change and not putting the spring clamps in the proper position. The clamp should be up close to the flared end of the tube under the hose. Not on top of it or far back. If you place it too far back the hose can weep coolant.

 

Another spot to check is the 90 degree fittings on the heads. There are 4 on top and 4 on the bottom. These are threaded in place and can and do weep especially after someone has been tugging and twisting on them during a hose change. I have re-sealed many. You may see a slight amount of dried coolant around the fitting base. Many times you may not right after a flight because the air movement through the cowl keeps it blown off, but if you wait a bit the pressure in the system will make it ooze out a tad. If you need to re-seal this just drain the top half of the coolant in the engine. Remove the fitting. Use a heat gun or butane torch to heat the fitting base and unscrew it. The clean the threads and use some Loctite 243 blue or 640 green. 640 is far better and I don't use 243.

[hbertoni]

Are you sure it's the hoses, or is it leaking around the threads of the fixtures? You can try buying new clamps, or put another clamp on for good measure.

 

As for the overflow tank: no matter what height it is mounted at, at least checking fluid level periodically is advised. If the relief cap leaks, it will spill out fluid, or be unable to draw any back in. That's why rotax recommends checking before each flight. In addition, your leak is too slow to generate enough suction to draw from the tank. The overflow bottle's purpose is to absorb surges in coolant level due to vaporization in hot areas, not to act as a standby reservoir. That's what the overflow assembly (the splitter) on top of the engine is for.

 

As a side note: if your CHT reads higher than normal, checking coolant should be the first thing you do. A guy hosed a brand new engine that is now sitting at Lockwood as a training engine, because he ignored the CHT warning. The engine ran 3 straight hours through aggressive touch and goes and speedy flight, and the owner went back the next day to do it again when he noticed it wasn't developing power. It warped the hell out of the heads and trashed the engine.

[hbertoni]

Thanks for the info on the overflow tank.

 

I do watch the CHT and discovered the extent of the leak problem when they went up.

 

I did track the leak down to one place where a rubber hoses connects to one of the Al tubes connected a head, and one place where a hose connects to the radiator. 

[Anticept]

Pretty common for a leak near the heads. Do as roger suggests before getting new clamps or anything.

[Tom Baker]

There was a version of the 90 degree hose on the front left cylinder that had a smaller wall thickness that needed a new smaller clamp to make it seal. Rotax had a change in the part number for the clamp for the new hose, but I didn't figure that out untill it was too late.

[Anticept]

There was a version of the 90 degree hose on the front left cylinder that had a smaller wall thickness that needed a new smaller clamp to make it seal. Rotax had a change in the part number for the clamp for the new hose, but I didn't figure that out untill it was too late.

 

That might explain why we have a seep on that side . I'll look into it, thanks!

[Runtoeat]

Tom, do you have the part no. for the new, smaller, clamp?

 

Clamps were repositioned (positions both near and far from expanded tube ends were tried), multiple clamps were installed and tube joints at heads were checked on my friend's CTLS, as Corey and Roger describe.  Leaks persisted where rubber hoses connected to the metals tubes.  Leaks were stopped when hoses from a different manufacturer were installed with latest clamps offered by Rotax.

[Roger Lee]

If you have a leak at that fitting (top 90 degree on #2 cyl) it is okay to use a wormdrive type clamp. Use one like we have on the other coolant hose that have the raised rip type. No serrated type clamps.

I buy these from Wurth USA. You can buy Worth hose there to if you want.

 

See picture. Use the one on the right.

 

p.s.

I haven't had any issues over the years using the stock spring clamp on any of the 90 degree hose on this fitting when the clamp is placed in the correct position.

 

Just a thought:

Depending on how you fell about hoses and internal spring usage which is a common practice (the CT has 2-3 springs in coolant hoses already) this could be another place you could use the better thicker wall 17mm coolant hose with a spring inserted and still use the stock outside spring clamp. It would eliminate any thin wall 90 degree hose and allow the clamp to do a much better sealing job.

[kentuckynet]

http://www.wurthusa.com/web/en/website/produkte_1/service___repair/hose_clamps/hose_clamps.php

 

Roger, which clamp is it...the one of yours on the right?

[Roger Lee]

They are Wurth "Zebra" clamps. They come in different sizes measured in mm. Just get the right size for either the 1" or 17mm coolant hose.

 

You can just do a search.

 

 

http://www.shopwurthusa.com/wurthstorefront/Service-and-Repair-Parts/Clamps/Zebra/Zebra-Hose-Clamp-16-25MM/p/054921625

[Tom Baker]

The new Rotax spring clamps are 851-645. When I ran into this issue the old clamps would simply slide over the hose before the hose was on the nipple. With the old hose you had to compress the clamps to slide it over the hose. The new clamps are slightly smaller with more tension. The new hose may have been one sourced by Lockwood rather than a genuine Rotax part, but I don't know this as fact. The last hose I got from Leading Edge Airfoils was back to the thicker wall thickness.

[AuntPeggy]

We're having this problem, too.  Why is a Zebra clamp better than a screw clamp?  It looks like they would both put the same force on a hose.

[FlyingMonkey]

We're having this problem, too.  Why is a Zebra clamp better than a screw clamp?  It looks like they would both put the same force on a hose.

 

I'm guessing the raised area of engagement allows the worm mechanism to work without potentially cutting into the hose beneath.

[Anticept]

Fuel injector clamps work better because the pinching action is more uniform. Both tabs are pulled together evenly.

 

A hose clamp/worm drive applies force more on the tab side being pulled by the screw, as the screw side rubs against the hose and has to overcome friction. So what ends up happening is you are trying to tighen a clamp by pulling it around the hose, instead of pinching it as with a fuel injector clamp.

 

I like worm drives simply because i only need a few sizes as they are versatile, whereas fuel injector clamps need a small warehouse.

[Roger Lee]

You probably can't find a fuel injection clamp for the larger 17mm or 1" hose. The Zebra clamp won't slip if tightened too much, won't cut into the hose and gives a better full circumference seal.

 

Save the old cruddy serrated wormdrive clamp for the garden hose.

[Tom Baker]

You probably can't find a fuel injection clamp for the larger 17mm or 1" hose. The Zebra clamp won't slip if tightened too much, won't cut into the hose and gives a better full circumference seal.

 

Save the old cruddy serrated wormdrive clamp for the garden hose.

The Zebra clamps if tightened to much will strip and not hold tension. Be careful tightening them, especially the second time around.

[Anticept]

You probably can't find a fuel injection clamp for the larger 17mm or 1" hose. The Zebra clamp won't slip if tightened too much, won't cut into the hose and gives a better full circumference seal.

 

Save the old cruddy serrated wormdrive clamp for the garden hose.

Maybe i am being stupid, but zebra clamps look like the worm drives i have always used. Whats the diff?

[hbertoni]

The new Rotax spring clamps are 851-645. When I ran into this issue the old clamps would simply slide over the hose before the hose was on the nipple. With the old hose you had to compress the clamps to slide it over the hose. The new clamps are slightly smaller with more tension. The new hose may have been one sourced by Lockwood rather than a genuine Rotax part, but I don't know this as fact. The last hose I got from Leading Edge Airfoils was back to the thicker wall thickness.

Top Gun you got it right.  It is the hose on the left front cylinder, and in the hose replacement they went from the old style spring clamp to adjustable screw clamp made of stainless steel.  I tighten it at some day time temperature, and on colder nights the aluminum pipe contracts more than the clamp and the leaking occurs.  What is needed is an aluminum or spring clamp that contracts with the aluminum pipe.

 

Henry

[procharger]

I was told by my AP that the metal tubes with hoses attached can leak if someone used a screwdriver to try to loosen the hose off the metal

tube, a slight scratch on the metal  tube can cause a leak not sure???

[Tom Baker]

Maybe i am being stupid, but zebra clamps look like the worm drives i have always used. Whats the diff?

I'm pretty sure that the Zebra clamps are what Flight Design uses as standard equipment.

[Anticept]

I was told by my AP that the metal tubes with hoses attached can leak if someone used a screwdriver to try to loosen the hose off the metal

tube, a slight scratch on the metal  tube can cause a leak not sure???

 

It can.

 

The easiest way to remove hoses is to use the flat side of the screwdriver against the end of the house, and push the hose off. Don't put the screwdriver between the hose and the fitting and definitely do not pry! If you absolutely must put something between the hose and fitting because of a sticky hose, use something that has a rounded tip, and run it around the circumference while pushing on the hose. Having someone apply a little bit of pulling force can also help!

 

While I was out at LEAF for my training, Brett found a hand pick that had a 90 degree tip, with a hump in the middle of the tip. It fit PERFECTLY around the fittings, and made pushing the hose off effortless.

 

I'm pretty sure that the Zebra clamps are what Flight Design uses as standard equipment.

 

Even when I buy clamps for certified aircraft from Lane Aviation, they still look the same as the pictures of the zebra clamps. Hex head and everything. Maybe the difference is as subtle as a phillips vs a reed and prince?

[Roger Lee]

Wurth Zebra clamps are what FD uses from the factory. I have learned to really like them and I buy 100 at a time. You can use them for applying header wrap cloth too.