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Coolant overheating

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kheindl(at)msn.com
Guest

Posted: Sat Jul 26, 2008 4:36 am Post subject: Coolant overheating

I have been unable to solve my overheating problem:

 I had replaced all glycol coolant and all hoses. Ever since then the coolant temperatures on the ground and in the climb are way ahead of the oil temperature.

 After warming up the engine the coolant is typically 25 C (45 F) hotter than the oil. The oil and cylinder head temperatures are always normal. Only in the cruise am I getting normal readings. The coolant temp. probe is in the coolant and is accurate.

 I have run out of ideas. Has anyone got any clue about this mystery ?

  

 Cheers C

  

 Karl

  

 

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ptag.dev(at)tiscali.co.uk
Guest

Posted: Sat Jul 26, 2008 1:17 pm Post subject: Coolant overheating

Hi! Karl  

Have you blocked the gap between cowl and underside of oil cooler?  

Bob H   

   

--

kheindl(at)msn.com
Guest

Posted: Sat Jul 26, 2008 1:57 pm Post subject: Coolant overheating

Bob C

  

 I certainly have C plus all the other gaps near the air intake. I sealed off the gills and opened up the area at the

 bottom aft of the radiators for main exit.

  

 Karl



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 From: ptag.dev(at)tiscali.co.uk

To: europa-list(at)matronics.com

Subject: RE: Coolant overheating

Date: Sat C 26 Jul 2008 22:13:02 +0100

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Hi! Karl 

Have you blocked the gap between cowl and underside of oil cooler? 

Bob H  

  

--

craigb(at)onthenet.com.au
Guest

Posted: Sat Jul 26, 2008 2:44 pm Post subject: Coolant overheating

Karl, just a  thought here, but do you KNOW your temp sender is correct, IE stuck it in a  pot of just boiled water which you can know the

 temp of  between one or two degrees of error and subjected it to vibration etc by shaking  it etc. When I was racing we had problems from time to time with faulty sender  units that would

 vary by as  much as 20 deg C. and this variation would change across minutes or even  instantly in some cases. It was a major pain to

 work with,  when you expect an engine to be running close to max temps, and then it spikes  20 degrees over max. Might i suggest

 you try a  fluid filled type sealed unit to run as a comparison so you can see if there is  a difference. 

  

 The other  thing i would be looking at if you believe the temps are accurate, is your spark  timing, excessively advanced timing will cause high temps at low RPM. ie warm  up

 and taxi. but  will not be as noticable at higher RPM. I have seen 20 - 30 degree  C increase in temps from around 5 degrees of advance from say 10 to 15  degrees BTDC. high

 levels of  spark timing advance are generally helpfull at higher RPM but not much benefit  at low RPM.  Some of the modern bike engines vary spark timing by as  much

 as 20 degrees  depending on conditions. 

  

 hope this  helps

  

 craig

 [quote]   --

kheindl(at)msn.com
Guest

Posted: Sat Jul 26, 2008 3:50 pm Post subject: Coolant overheating

Hi Craig C

  

 I am quite sure about the temperature. When it reaches about 120 C it boils over into the overflow bottle C 

 which is what I would expect. And in the cruise it is normal.

 The ignition timing is something new and I wouldn't know how to check that. The engine is running just fine.

 I will fly over to the Rotax agent this coming week and see if he has any ideas.



 Cheers C

  

 Karl

  

 

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 From: craigb(at)onthenet.com.au

To: europa-list(at)matronics.com

Subject: RE: Coolant overheating

Date: Sun C 27 Jul 2008 08:47:25 +1000

   .ExternalClass .EC_hmmessage P {padding-right:0px;padding-left:0px;padding-bottom:0px;padding-top:0px;} .ExternalClass BODY.EC_hmmessage {font-size:10pt;font-family:Tahoma;}   Karl C just a thought here C but do you KNOW your temp sender is correct C IE stuck it in a pot of just boiled water which you can know the

 temp of between one or two degrees of error and subjected it to vibration etc by shaking it etc. When I was racing we had problems from time to time with faulty sender units that would

 vary by as much as 20 deg C. and this variation would change across minutes or even instantly in some cases. It was a major pain to

 work with C when you expect an engine to be running close to max temps C and then it spikes 20 degrees over max. Might i suggest

 you try a fluid filled type sealed unit to run as a comparison so you can see if there is a difference. 

  

 The other thing i would be looking at if you believe the temps are accurate C is your spark timing C excessively advanced timing will cause high temps at low RPM. ie warm up

 and taxi. but will not be as noticable at higher RPM. I have seen 20 - 30 degree C increase in temps from around 5 degrees of advance from say 10 to 15 degrees BTDC. high

 levels of spark timing advance are generally helpfull at higher RPM but not much benefit at low RPM.  Some of the modern bike engines vary spark timing by as much

 as 20 degrees depending on conditions. 

  

 hope this helps

  

 craig

 [quote] --

craigb(at)onthenet.com.au
Guest

Posted: Sat Jul 26, 2008 5:23 pm Post subject: Coolant overheating

I am sure the  Rotax people would be able to check the timing in a couple of  minutes.

 given I  havent had a chance to get a really close look at a rotax engine I couldnt  comment on how they set the initial spark timing, If you had access  to

 a pully or  flywheel that runs at crankshaft speed it would be possible to create your own  timing marks, but it requires you to remove valve covers and a spark  plug so you

 can determine  when cylinder 1 is at TOP Dead Centre (ie when the fuel air mix would be burning  if the engine was running)mark the pully or flywheel

  then  coming back the correct number of degrees and creating a mark or  pointer on a fixed part of the engine next to the pully/flywheel. You can then  use an inductive pickup

 timing light  that will detect the spark pulse running to the plug and flash a strobe beam in  time with the spark. Point the light at your timing mark with the engine  running and you

 can see the  mark on the pully and the pointer should line up each flash of the  stobe.  

 As for the  engine running fine, it may actually run slightly better that normal at  higher rpm as the advanced spark gives the fuel air mix longer to burn, too  much advance

 is a bad  thing though as it is much the same as your engine pre-igniting which can happen  with lower rated fuels which can do damage to your  engine.

  

 good  luck

  

 craig   

 [quote]   --

kheindl(at)msn.com
Guest

Posted: Sat Jul 26, 2008 6:05 pm Post subject: Coolant overheating

Craig C

  

 If it is the timing C would it not also affect the cylinder head temperature ? I don't know much about engines.

 What about a faulty water pump or an airlock.

  

 Karl



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 From: craigb(at)onthenet.com.au

To: europa-list(at)matronics.com

Subject: RE: Coolant overheating

Date: Sun C 27 Jul 2008 11:26:16 +1000

   .ExternalClass .EC_hmmessage P {padding-right:0px;padding-left:0px;padding-bottom:0px;padding-top:0px;} .ExternalClass BODY.EC_hmmessage {font-size:10pt;font-family:Tahoma;}   I am sure the Rotax people would be able to check the timing in a couple of minutes.

 given I havent had a chance to get a really close look at a rotax engine I couldnt comment on how they set the initial spark timing C If you had access to

 a pully or flywheel that runs at crankshaft speed it would be possible to create your own timing marks C but it requires you to remove valve covers and a spark plug so you

 can determine when cylinder 1 is at TOP Dead Centre (ie when the fuel air mix would be burning if the engine was running)mark the pully or flywheel

  then coming back the correct number of degrees and creating a mark or pointer on a fixed part of the engine next to the pully/flywheel. You can then use an inductive pickup

 timing light that will detect the spark pulse running to the plug and flash a strobe beam in time with the spark. Point the light at your timing mark with the engine running and you

 can see the mark on the pully and the pointer should line up each flash of the stobe.  

 As for the engine running fine C it may actually run slightly better that normal at higher rpm as the advanced spark gives the fuel air mix longer to burn C too much advance

 is a bad thing though as it is much the same as your engine pre-igniting which can happen with lower rated fuels which can do damage to your engine.

  

 good luck

  

 craig   

 [quote] --

rlborger(at)mac.com
Guest

Posted: Sat Jul 26, 2008 6:06 pm Post subject: Coolant overheating

Europaphiles,



The Rotax 9xx engines have a fixed timing determined electronically by tabs on the flywheel & sensors on the frame.  See my build web page in the signature block.  I have an album on the Rotax 9xx school.  On the first page of the album are pics and comments on the timing system.

Good building and great flying,

 Bob Borger

Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S

http://www.europaowners.org/N914XL

(99.9% done) Presently fighting gremlins in the starting circuit.

3705 Lynchburg Dr.

Corinth, TX  76208

Home:  940-497-2123

Cel:  817-992-1117

 



On Jul 26, 2008, at 20:26, craig bastin wrote:

[quote]I am sure the Rotax people would be able to check the timing in a couple of minutes.

given I havent had a chance to get a really close look at a rotax engine I couldnt comment on how they set the initial spark timing, If you had access to

a pully or flywheel that runs at crankshaft speed it would be possible to create your own timing marks, but it requires you to remove valve covers and a spark plug so you

can determine when cylinder 1 is at TOP Dead Centre (ie when the fuel air mix would be burning if the engine was running)mark the pully or flywheel

 then coming back the correct number of degrees and creating a mark or pointer on a fixed part of the engine next to the pully/flywheel. You can then use an inductive pickup

timing light that will detect the spark pulse running to the plug and flash a strobe beam in time with the spark. Point the light at your timing mark with the engine running and you

can see the mark on the pully and the pointer should line up each flash of the stobe.  

As for the engine running fine, it may actually run slightly better that normal at higher rpm as the advanced spark gives the fuel air mix longer to burn, too much advance

is a bad thing though as it is much the same as your engine pre-igniting which can happen with lower rated fuels which can do damage to your engine.

 

good luck

 

craig   

[quote]--

craigb(at)onthenet.com.au
Guest

Posted: Sat Jul 26, 2008 7:05 pm Post subject: Coolant overheating

I theory yes,  but if the coolant really is the indicated temp, then given the air and water  cooling, I would expect the whole engine to be running  hotter

 but this isnt  the case is it. Do you have an EGT, it would be interesting to see if there is  any large change in EG temps from climb to cruise if you didnt  alter

 mixture or  throttle. I would doubt it would be an airlock as this normally would give you a  localised HOT Spot with perhaps one cylinder running hot (also not the case  according to your CHT)

 a worn out  water pump can give some weird results but unless the impeller is slipping at  certain RPM again you would expect higher temps almost all the time, unless you  are getting enough

 air only  cooling in cruise flight to overcome low water flow rates. Excessively high flow  rates can also give you high coolant temps as the water passes through the  radiator too fast to be cooled

 effectively  at low speeds this is normally caused by a jammed or broken thermostat that  controls water flow based on temperature (same as in your car) if your  engine takes longer to warm up

 than it used  to and then runs hotter I would suspect that, but I dont believe the 9XX engine  use a thermostat, given the low cruise temps (50 deg C) some are  reporting.

  

 I still  believe it worth while to try a fluid filled temp gauge with a bulb you  insert into the water line and tube back to the gauge, just to confirm your  water temps are accurate. This will be

 quick, easy  and cheap to do, you can get one from most auto parts stores for around $25.  That way you know you are correct, and not being tricked into thinking you  have a coolant

 problem, when  it could be an electrical problem giving you a false reading to high  temps.  

 [quote]   --

carl(at)flyers.freeserve.
Guest

Posted: Sun Jul 27, 2008 12:08 am Post subject: Coolant overheating

Hi Karl,

  

 I havent been following this thread so I may have missed  something.

  

 Firstly is it a new installation - ie: has the aircraft  flown before and everything was normal (temperature wise). Is it a Mono or a  trigear (ie: does it sit on its tail or is it level)

  

 My guess is you definitely have an airlock somewhere. Have  you removed the air pocket from the port radiator return hose (to the water  pump)? To do this you need to ease the hose off the radiator connection and  release all the trapped air in the hose. It can be done by jamming a large  screwdriver in the top of the hose where it connects the rad - loosen the  jubilee clip first and slide it out of the way. Presumably none of the hoses are  kinked or crushed (by the engine frame)

  

 If you have a big airlock the cooling system may be  working but only intermittently - the angle of climb/ descent of the aircraft  may affect this. Unless the airlock is cleared the coolant flow will always be  restricted, but be adequate in the cruise when the engine is running  cooler.

  

 The only other possibility (unlikely) is a blockage or a  problem with the water pump.

  

 If you remove the radiator cap (when the engine is cold)  it should be possible to see the coolant pumping round while the engine is  idling but this wont tell you if there is sufficient flow (just that there isnt  a major blockage). MAKE SURE YOU TAKE THE NECESSARY SAFETY PRECAUTIONS REGARDING  THE MOVING PROPELLER - I know its stating the obvious but I dont want your death  on my hands.

  

 It might be worth draining and refilling the cooling  system and backflushing everything with a high pressure hose.

  

 Just my ten cents worth.

  

 Carl Pattinson

 G-LABS.

 [quote]   ---

kheindl(at)msn.com
Guest

Posted: Sun Jul 27, 2008 5:55 am Post subject: Coolant overheating

Hi Carl C

  

 Thank you for your input C I am hoping it is something simple like an airlock.

 I have a trigear/912S with close to 300 hours C with no previous problems of this nature. For my last annual I decided

 to change coolant (glycol 50/50) and oil C and all hoses and fuel lines. I had also made changes to improve airflow over 

 the engine C at the same time reducing drag. I have since then removed those changes again C but this has made no difference.

 On the contrary C the temperature seems to be even higher.

 You seem to have had firsthand experience with that problem ? I will try to follow your guidelines C hoping for success.

 I just don't want to spill a lot of coolant all over the engine. One idea is to remove the coolant - I have a pump and I can

 feed the extraction hose right down to the radiator - and then refilling the radiator first C and then the rest.

 I will keep all informed.

 Best regards C  Karl

  

 



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 From: carl(at)flyers.freeserve.co.uk

To: europa-list(at)matronics.com

Subject: Re: Coolant overheating

Date: Sun C 27 Jul 2008 09:05:37 +0100

   .ExternalClass .EC_hmmessage P {padding-right:0px;padding-left:0px;padding-bottom:0px;padding-top:0px;} .ExternalClass BODY.EC_hmmessage {font-size:10pt;font-family:Tahoma;}   Hi Karl C

  

 I havent been following this thread so I may have missed something.

  

 Firstly is it a new installation - ie: has the aircraft flown before and everything was normal (temperature wise). Is it a Mono or a trigear (ie: does it sit on its tail or is it level)

  

 My guess is you definitely have an airlock somewhere. Have you removed the air pocket from the port radiator return hose (to the water pump)? To do this you need to ease the hose off the radiator connection and release all the trapped air in the hose. It can be done by jamming a large screwdriver in the top of the hose where it connects the rad - loosen the jubilee clip first and slide it out of the way. Presumably none of the hoses are kinked or crushed (by the engine frame)

  

 If you have a big airlock the cooling system may be working but only intermittently - the angle of climb/ descent of the aircraft may affect this. Unless the airlock is cleared the coolant flow will always be restricted C but be adequate in the cruise when the engine is running cooler.

  

 The only other possibility (unlikely) is a blockage or a problem with the water pump.

  

 If you remove the radiator cap (when the engine is cold) it should be possible to see the coolant pumping round while the engine is idling but this wont tell you if there is sufficient flow (just that there isnt a major blockage). MAKE SURE YOU TAKE THE NECESSARY SAFETY PRECAUTIONS REGARDING THE MOVING PROPELLER - I know its stating the obvious but I dont want your death on my hands.

  

 It might be worth draining and refilling the cooling system and backflushing everything with a high pressure hose.

  

 Just my ten cents worth.

  

 Carl Pattinson

 G-LABS.

 [quote] ---

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