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Keith W

Running Hot

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Hi just did the 5 year rubber hose replacement on my gazelle and now it's running very hot coolant temp, anybody got any ideas on how to bleed the coolant system I reckon it's prolly got an airlock thanks Keith.

 

 

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Hi just did the 5 year rubber hose replacement on my gazelle and now it's running very hot coolant temp, anybody got any ideas on how to bleed the coolant system I reckon it's prolly got an airlock thanks Keith.

Hi Keith

 

Don't take this as a silly comment; but did you look inside all the hoses before fitting as there could have been some packing or other material inside a hose especially the longer hoses.

 

Cheers

 

Mike

 

 

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Hi just did the 5 year rubber hose replacement on my gazelle and now it's running very hot coolant temp, anybody got any ideas on how to bleed the coolant system I reckon it's prolly got an airlock thanks Keith.

Hi,

 

Best check with Floods for the best method, I would think.....

 

Cheers

 

Neil

 

 

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Thanks everyone seems it is an airlock because the header tank is not much higher than the radiator,folded the wings to sit it on its tail, took the cap of and give it a good shake, hopefully this will fix it but the weather will stop me flying for a while.

 

 

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If it's a 912, you can do some bleeding by lifting the header tank gently, with the cap off (cold of course) and squeezing the four hoses that go to the heads.

 

 

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Finely got to fly the gazelle yesterday, the 912 ran beautiful but still ran hot, I have bled the coolant system as best I can and I'm running evans coolant, on climb out the temp goes up when you pull some throttle back to 5000 rpm it comes back a bit and at idle. on final it comes way back but after 4 circuits thought it best to to pull the pin as the temp was slowly building. The air temp was 33 degrees and very humid might try extending the sides of the shroud to try and funnel more air through the radiator, open to suggestions cheers Keith.

 

 

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Set the craft up so one side is noticeably higher than the other, remove rad cap, let engine idle, for a few minutes, then shut it down, and do the same thing to other side.

 

Have seen this method on several types, and it worked ok.

 

 

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Keith:

 

I'm probably telling you something that you already know, but circuits on a reasonably warm day aren't going to give you a fair indication of your cooling situation.

 

On my plane, I find it takes 10 minutes or so at a level cruise speed before my temps come back to normal and stabilise. While ever I'm doing climbs and descents my temps are all over the place and there often seems to be no rhyme or reason to it.

 

I flew yesterday morning and my coolant temp never went below 105C even when I was stooging around at 4,600RPM. The oil temp dropped way back to just over and under 90C for most of the session though.

 

I'm beginning to suspect that the coolant temp is a product of RPM and outside temp, but the oil temp seems to be related to how hard the engine is working. For example, if I do an extended climb at about 5,000RPM, my coolant temp doesn't rise all that much but the oil temp goes up. But if I'm level cruising at 5,000RPM the oil temp stabilises at a lower value.

 

 

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When I removed the cowling after I finished my circuits the radiator didn't seem as hot as the rest of the engine, does anybody know how much coolant it should hold read the manual but can't find a capacity any where Keith.

 

 

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Did you change to Evans coolant from a water based type? If so this may also explain higher temps. Evans has a lower thermal efficiency than water and will subsequently run hotter.

 

 

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A Rotax powered RV 12 that was using evans coolant was also running very hot as soon as they got rid of the evans and went back to glycol the temps were normal

 

 

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105 dec C coolant temp is normal if using evans, and 90 dec C for oil is spot on. on long climbs at full throttle, i will see oil at about 110 to 120 in summer, but barely move from 90 in winter, i have rarely seen the coolant temps move from 110.

 

Max oil temp is 140, min 50.

 

Max coolant temp with evans is 135C, max with water is 120c

 

 

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Can any body tell me are the radiators in the gazelles made from aluminium or copper or brass, also what coolant other than Evans does anybody run, thanks Keith.

 

 

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105 dec C coolant temp is normal if using evans, and 90 dec C for oil is spot on. on long climbs at full throttle, i will see oil at about 110 to 120 in summer, but [FLOATL]barely[/FLOATL] move from 90 in winter, i have rarely seen the coolant temps move from 110.4

 

Max oil temp is 140, min 50.

 

Max coolant temp with evan[FLOATL][/FLOATL]s is 135C, max with water is 120c[/quote

 

I thought the normal temps were cylinder head temps not coolant temps. You would need an extra sensor in line with the coolant systems liquid to get the coolant temperature.

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Im running glycol 50/50 water in LCH in a 3300 Coolant temp 102 to 120.

 

Head temp , seperate sensors , 90/100 c.

 

Oil temp 90/110 , the oil temp thermostat warms the oil on a cold day to 80 deg .

 

Takes 10 mins to warm to 50 c

 

Radiator is aluminium ,

 

Davies craig water pump 80 lts min ,

 

( over kill at 7 amp draw )

 

Realy only needs about 40 lts min ,

 

Carnt seem to sorce a smaller one,

 

 

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Be careful that coolant temp and head temps are not confused on Rotax 912.

 

The sensor that screws into a dry hole (except new type heads)in the head is the CYLINDER HEAD TEMPERATURE I believe...

 

 

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Drained the Evans coolant and replaced it with Nulon llr, with the air temperature about 32 the cylinder head temp was 110 at cruise but got to 125 on climb outand spat a lot out of the plastic bottle, oil temp was 100, think I will have to run the evans, has any one made any baffles for a gazelle to try and force more air through the radiator, or fitted another radiator or moved it to a position where it can get more air flow rather than at the back of the motor where it hardly gets any air, I don't know what skyfox was thinking mounting where they did, open to suggestions cheers Keith.

 

 

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Drained the Evans coolant and replaced it with Nulon llr, with the air temperature about 32 the cylinder head temp was 110 at cruise but got to 125 on climb outand spat a lot out of the plastic bottle, oil temp was 100, think I will have to run the evans, has any one made any baffles for a gazelle to try and force more air through the radiator, or fitted another radiator or moved it to a position where it can get more air flow rather than at the back of the motor where it hardly gets any air, I don't know what skyfox was thinking mounting where they did, open to suggestions cheers Keith.

Hi Keith,

 

Not sure you can make such changes to a 24 rego aircraft....

 

Cheers,

 

Neil

 

 

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Drained the Evans coolant and replaced it with Nulon llr, with the air temperature about 32 the cylinder head temp was 110 at cruise but got to 125 on climb outand spat a lot out of the plastic bottle, oil temp was 100, think I will have to run the evans, has any one made any baffles for a gazelle to try and force more air through the radiator, or fitted another radiator or moved it to a position where it can get more air flow rather than at the back of the motor where it hardly gets any air, I don't know what skyfox was thinking mounting where they did, open to suggestions cheers Keith.

 

Hi Keith..I believe the 80 hp gazelle if fitted with the radiator cooling kit(shroud on sides of radiator and oil cooler) requires coolant at 80/20 Glycol/water..

 

Most installations require around 2 ltrs..Oil temp should operate between 90/110 c and CHT temp the same with max to 140c..

 

Unmodified cooling system requires 100% Glycol or it will spit the coolant out.. Not sure about Evans as i have not come across anybody using it in a gazelle or Skyfox. With regards air entrainment i think its recomended to lower the tail and bleed the system.

 

Regards Richard..

 

 

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Hi Neil was worried about that what do you run in your Gazelle and what sort of temps do you get , was going to fly to Penfield a couple of weeks ago but the weather was against me Keith.

 

 

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Thanks Richard my gazelle has a shroud on the radiator that I have widened one side, no shrouds on the oil cooler, with the evans coolant in it if the air temperature was above 30 it would run cht temps above 125 whi ch is fine for the evans but I was worried about the rest of the engine with so high temps

 

 

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Hi Neil was worried about that what do you run in your Gazelle and what sort of temps do you get , was going to fly to Penfield a couple of weeks ago but the weather was against me Keith.

Hi Keith,

 

We have not done any mods to our radiator setup. We run 50/50 Castrol Radicool (formerly called AntiBoil AntiFreeze) and distilled water, and we get temps in cruise around 100 degrees. It gets a bit hotter on a long climb, but returns to the 100 afterwards. The level in the overflow bottle stays pretty constant at the MIN mark (or a little above), but we do not fill the system up beyond that as it can expand and come out the overflow vent. From what we understand it should not be topped up beyond about a third up the bottle for that reason. Make sure you have the 1.2 bar radiator cap (SB-912-043 Nov 2006) and the correct size vent hole in the overflow bottle lid (as per SB-912-039 Dec 2002)

 

Feel free to come over to Penfield and have a look at our Gazelle - give me a PM if you intend to. I can do most days apart from Tuesdays.

 

Cheers,

 

Neil

 

 

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Evans will run hotter because it doesn't carry as much heat away as water. The same applies to oil cooling. The boiling point of water is too low for an engine to run at an efficient temperature so it may have an additive and a pressure cap. You introduce a few problems by pressurising it, one being that it easily leaks and that at height it is only differential, so the actual pressure drops with height.

 

You can also get hot spots (steam pockets) in parts of the engine

 

Evans doesn't have any of these problems but the engine runs hotter. This may make it run more efficiently. Synthetic oils allow higher temps too with extra protection. Evans will not boil in the normal sense, and in theory would run with the cap off, without coolant overflow due pressure, as there isn't any, except a small amount from the pump. Nev

 

 

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