CYLINDER HEAD OVER-TEMP AFTER HOSE CHANGE

[MileHighCTLS]

During my last annual I did the 5-year changeout of hoses, which included all coolant hoses. I completed everything in March, when the weather was still cool here in Denver. I few times, with no temp problems.

Yesterday, when OAT was around 80-degrees, I did about 8 touch & goes. No temp problems while flying. However, while taxiing back to hangar the CHTs went up to around 250 and I got a red flashing light, then within a minute went back down to normal, then after a minute, went back up to over 250. I figured the readings were too erratic, too quickly to be the actual head temps, and figured it was the probes? But I don't think both probes would go out at exactly the same time. BTW, during the entire time, oil temp was normal.

Back at the hangar I took the cowling off and examined the engine. I noticed the coolant expansion tank had spewed out coolant from the tiny air hole and the expansion tank was completely filled all the way up to the cap. Later that day, after the engine cooled off, the level in the expansion tank went back to mid-range.

An important note:  When I changed out the coolant lines, I simply filled up the top coolant tank and the expansion tank. I did not "purge" the system. Was I supposed to? I could not find a procedure for doing that. Could air in the system cause this problem?

Any wisdom you can impart on the topic will be most appreciated.

[Tom Baker]

Sounds like the thermostat sticking. I've had one airplane where I have had to replace it twice. The thermostat is an automotive type in the aluminum housing on the left side of the engine. 

[MileHighCTLS]

I removed it in 2-minutes. It seems to be in great condition. Moves well. Spring seems very strong. Can you tell with these things visually?

And does anyone have the automotive part number?

[MileHighCTLS]

One more thing ... do we even need a thermostat? What's the consequence of running without it at our mile-high airports? Not sure the engine would ever be too cold? 

Thoughts?

[Tom Baker]

You don't need the thermostat, but you can't just remove it from the housing because of the way it is plumbed. I don't have the part number handy, but I think I have posted it before.

[MileHighCTLS]

Thanks I you so much for the info!  BTW, do you know the temp rating?

[Tip]

We replaced LSBruce’s at Page one year. He bought it at an automotive store, but we had to drill a bypass hole in it.

[Anticept]

Blow out the radiator with mineral spirits then follow up with isopropyl.

Also, a thermostat doesn't work on the spring, it's the parrafin inside of it that does the magic. Drop one in water and then turn the heat up. If it boils before the thermostat moves, you have a bad thermostat.

The thermostats are permacool devices, you can get replacement parts from them or at least ask about them.

They're 185 degree or thereabouts units.

[LS Bruce]

My 2008 CTLS was overheating far away from home.

I called Flightdesign USA. They said just go to your local NAPA car parts store and get a Ford thermostat, Napa #238.

I got the 180 degree version, drilled the 1/16 bleed hole. Worked good. Still in there today.

[Tip]

14 minutes ago, LS Bruce said:

My 2008 CTLS was overheating far away from home.

Hey Bruce, tell them why it was over heating?

[MileHighCTLS]

UPDATE:  Upon a close examination of the thermostat that came with my CTLS, I found the brand name, "Wahler" and the designed temp 80C.

I was able to find an exact replacement at AutohausAZ, in Arizona.

NOW ANOTHER QUESTION:  Once I install it, and fill the system with coolant, the thermostat will be closed. I assume I fill up the spider tank and the plastic expansion tank and run it up, then do it again if necessary? Or is there a trick to refilling the cooling system?

[Anticept]

Fill from the top of the engine a little bit below the lip, press the tubes on top of the engine to displace the air they have, fill to the lip, close it up, go fly.

Check again tomorrow, top off, it will be maybe half an inch down.

After the second top off, it shouldn't be needing coolant anymore.

DO NOT OPEN THE COOLANT SYSTEM WHILE ITS HOT UNLESS YOU LIKE HOSPITALS.

 

PS: What you linked is one that comes with a seal. Is it the seal or non sealing version? I don't recall them coming with seals. They're not meant to completely block flow, a safety in case it fails closed.

[MileHighCTLS]

9 minutes ago, Anticept said:

"PS: What you linked is one that comes with a seal. Is it the seal or non sealing version? I don't recall them coming with seals. They're not meant to completely block flow, a safety in case it fails closed."

The one I took out of the plane had a seal on it. And the one I ordered is an exact duplicate. I believe the only modification I need to do is that tiny weep hole in the flange.

[Anticept]

Got it thanks.