Blowing the Coolant out - Rotax 912 ULS

[Guest TopEnd]

So I have this issue. Lately my 912 has started spit bits of coolant out the overflow lid. But not really on flights under 2hrs. I just completed s 3 hr flight and the overflow bottle is empty. Header tank still has coolant. And the overflow was only filled exactly to the min line.

 

Temps on climb up to 120 CHT AND 100-110 on cruise.

 

Oil 105 on climb and and around 90 on cruise.

 

I have a new cap coming 1.2 bar and a new radiator extra two core from Bert Flood.

 

Anyone else had anything like this?

 

Cheers

 

Marty - Darwin NT

 

2005 with new Crankcase 2000TBO

 

ENGINE TT 880

 

 

 

 

[Downunder]

Hm... very hot heads. My oil temp is always quite a bit hotter than cht's. Hope you don't have a cracked head...

 

 

[cscotthendry]

If this was a car, I'd suspect a blown head gasket, but the rotax heads are self contained.

 

If you have a cracked head, you might spot it by doing the following:

 

Start with a cold engine and remove the reservoir cap. (don't remove the tank cap on a hot engine)

 

Check for a cracked head by having a compression leakdown test done. During the leakdown test, leave the pressure on each cylinder for a bit and check for bubbles in the coolant reservoir tank. This will tell you if there's a cracked head, and which cylinder is at fault.

 

120 Deg is getting up there temp wise for the CHTs, Are you running Evans coolant or gylcol/water?

 

 

[Guest TopEnd]

If this was a car, I'd suspect a blown head gasket, but the rotax heads are self contained.If you have a cracked head, you might spot it by doing the following:

Start with a cold engine and remove the reservoir cap. (don't remove the tank cap on a hot engine)

 

Check for a cracked head by having a compression leakdown test done. During the leakdown test, leave the pressure on each cylinder for a bit and check for bubbles in the coolant reservoir tank. This will tell you if there's a cracked head, and which cylinder is at fault.

 

120 Deg is getting up there temp wise for the CHTs, Are you running Evans coolant or gylcol/water?

Was on Evans but under Gary advice from Floods I have changed to 50/50. Lame doing leak test next week. It's a worry as I fly over the top end fairly remote quite a bit and want to get to the bottom of it asap.

 

 

[cscotthendry]

In my first plane, I ran Evans coolant. I always had higher temps than anyone else I knew, but Evans does that. My current plane uses the 50/50 and I wouldn't go back to the Evans.

 

Re-reading your post, I think you mad a good choice to replace the radiator cap. It's a cheap attempt at a fix and just might solve it.

 

From the pix, it's certainly made a mess of the plane!

 

Also, since you have had the overflow bottle go empty, make sure that your cooling system is topped up and bleed all the air out of the system. If there is any air in the lines, it could cause the coolant to boil easier, which causes steam which pushes more coolant out, which allows room for expansion, which causes lower boiling temps etc etc in a positive feedback loop.

 

 

[Guest TopEnd]

In my first plane, I ran Evans coolant. I always had higher temps than anyone else I knew, but Evans does that. My current plane uses the 50/50 and I wouldn't go back to the Evans.Re-reading your post, I think you mad a good choice to replace the radiator cap. It's a cheap attempt at a fix and just might solve it.

From the pix, it's certainly made a mess of the plane!

 

Also, since you have had the overflow bottle go empty, make sure that your cooling system is topped up and bleed all the air out of the system. If there is any air in the lines, it could cause the coolant to boil easier, which causes steam which pushes more coolant out, which allows room for expansion, which causes lower boiling temps etc etc in a positive feedback loop.

Thanks. Will do.

 

 

[planesmaker]

Have you just changed from Evans or been running 50/50 for a while then this happens?

 

 

[Guest TopEnd]

Have you just changed from Evans or been running 50/50 for a while then this happens?

Ok. Winding the clock back 3 months ago I was still on Evans. Had a midday take off from YDEA to YRNG. on the climb out the engine "smelt hot" and was just over 120 CHT. after returning to YMKT I observed a weep around the elbow into the head. Gary at Floods said to change o ring and re seal. All done and has been like this since.

 

 

[planesmaker]

Sounds like a cap. Temps are a bit on the high side though. What aircraft?

 

 

[Guest TopEnd]

Sounds like a cap. Temps are a bit on the high side though. What aircraft?

Fly Synthesis Texan 550

 

 

[Guest TopEnd]

The last flight before the coolant dump :;

 

 

 

[skippydiesel]

Sounds like a cap. Temps are a bit on the high side though. What aircraft?

Have you tried the new cap fix?? If so what result.

New cap can be purchased from BMW motorcycle dealers -

 

"Radiator cap is BMW P/N 17112345074 at about 1/2 of the Rotax price (fitted to BMW motorcycle F650 with Rotax engine)."