Engine oil running high temps

[rhtrudder]

On climb out I have high oil temps on my 914 when the air temp is in the 30's , wondering if it would help if I enlarged the small vent on top of my cowl to let some of the heat escape , head temps seem OK but the oil is climbing out of the green also the pressure drops back , once up to high altitude and levels off in the cold air it improves slowly

 

Greg

 

 

[SDQDI]

On climb out I have high oil temps on my 914 when the air temp is in the 30's , wondering if it would help if I enlarged the small vent on top of my cowl to let some of the heat escape , head temps seem OK but the oil is climbing out of the green also the pressure drops back , once up to high altitude and levels off in the cold air it improves slowlyGreg

Do you have your oil cooler partly blocked off? I keep mine half blocked off for winter but in summer it has to be fully open or it will make it out of the green on a long climb.

 

 

[rhtrudder]

Oil cooler is fully open but I do block it when it's winter

 

 

[gregrobertson]

Seems to me there is enough air going through the radiator to keep the CHT under control. You may need to reposition the oil cooler so that it is getting more air flow through it. I have the same problem with my 912 although I am still in the green but only just. A small lip on the bottom of the cowl can make a huge difference to the amount of air going through the cowls. Greg.

 

 

[rhtrudder]

The oil cooler is fully exposed but I reckon there is a lot of heat build up inside the cowl ,hard to start after shutdown on a hot day which I think is fuel vapourering from the carbs . These aircraft come out of Europe and maybe don't suit our hot weather , the cowl only has a 15mm by 100mm vent at the back just in front of the screen

 

Greg

 

 

[facthunter]

Increase the climb speed if the ROC stays reasonable. Synthetic oils have a much higher rated temp tolerance and a short period at around 100 will help get the moisture out of the oil. Nev

 

 

[gregrobertson]

The vent at the rear of the cowl (at the top) will certainly help to get rid of the hot air surrounding the engine after shutdown, increasing the size a little will help with heat soak but I'm not sure it is going to help while climbing out. It depends just where the oil cooler is mounted. Greg.

 

 

[facthunter]

I reckon the only thing that really works is an adjustable cowl flap for liquid cooled motors. It's good for the others too, but almost mandatory on the LCM. Nev

 

 

[RickH]

The oil cooler is fully exposed but I reckon there is a lot of heat build up inside the cowl ,hard to start after shutdown on a hot day which I think is fuel vapourering from the carbs . These aircraft come out of Europe and maybe don't suit our hot weather , the cowl only has a 15mm by 100mm vent at the back just in front of the screenGreg

If the only vent which allows egress of the air through the oil cooler is 15 x 100 mm you may well have to increase the size of that vent. Compare it to the size of the air inlet to the cooler. Think of it this way if the air can't get out then pressure build up (back pressure) inside the cowl is going to stop the air actually getting in.

 

 

[rhtrudder]

There is a bigger opening underneath but reckon the heat would have to build up under the top part of the cowl with the heat rising

 

Greg

 

 

[Ayecapt]

Make sure that is really overheating! By this i mean that my 912 seemed to be over heating on climbs but it turned out to be the oil temp sensor . They do play up in a couple ways. They can become less linear at the hot of the scale and indicate too hot whilst being ok when coldend , or they just read higher temps. It should be around 1000 ohms at 20 deg c .. It then lowers resistance as it gets hotter so 100 ohms drop will give around 10 deg rise in gauge reading. Just a thought for you to consider.

 

 

[Downunder]

Also, over propped (too course) can show as higher oil temp.

 

 

[Ultralights]

i use these, as backups in case of instrument failure..

 

 

 

have them stuck to strategic locations on the cooling and oil systems. one on the oil tank, each side of the oil cooler, and lines either side of the oil pump, and the same for the cooling system. either side of the radiator, inlet and outlet, and water pump as well as higher reading ones on the cylinder heads themselves.

 

cheap insurance as fas as im concerned. also, if you hav an issue with high temps somewhere, land and check the recorders, and find none are reading high, then you know you have an instrumentation problem

 

 

 

[planesmaker]

What aircraft do you have? Has it been ok in the past on hot days? Tom

 

 

[rhtrudder]

i use these, as backups in case of instrument failure..

 

have them stuck to strategic locations on the cooling and oil systems. one on the oil tank, each side of the oil cooler, and lines either side of the oil pump, and the same for the cooling system. either side of the radiator, inlet and outlet, and water pump as well as higher reading ones on the cylinder heads themselves.

 

cheap insurance as fas as im concerned. also, if you hav an issue with high temps somewhere, land and check the recorders, and find none are reading high, then you know you have an instrumentation problem

 

Where do you get these?

 

 

[rhtrudder]

What aircraft do you have? Has it been ok in the past on hot days? Tom

Plane is a sabre ,I think mine is the only one with a 914, there was another but was crashed , the rest ,5 maybe all have 912's . Now the weather has cooled off temps are good . I opened the vent up on the cowl but it didn't seem to make any difference , prop is variable pitch set full fine on climb out, revs to red line. There is a small gap between the cooler and cowl so I might try and fill it with foam before next summer, thanks for your help

 

 

[onetrack]

It's important to find out the exact engine oil temperature. Utilise a measuring device that is known and proven to be accurate.

 

It's important that you measure the actual oil temperature, not the metal it's in contact with. You can have oil that is hotter than the surrounding metal, when the engine is working hard and under temperature duress.

 

Ayecapt is right onto it, many gauges are just "indicators", their accuracy is suspect, often at each end of the dial.

 

Dinosaur oils start to break down and have reduced lubrication ability over 121 deg C (250 deg F ). Its lubricity drops rapidly for every 5.5 deg C (10 deg F) increase above 121 deg C (250 deg F). At 132 deg C (270 deg F) it's lost 55% of its lubricity.

 

Synthetic oils can go 28 deg C (50 deg F) higher than dinosaur oils before they start to lose their lubricity. However, this still means that at 149 deg C (300 deg F), synthetic oil is also starting to lose its lubricity.

 

It's also important to remember that engine operating clearances continue to increase with increased temperatures.

 

As a result, very high engine temperatures can increase bearing clearances substantially, to the point where the bearing-to-journal gap is big enough to create a hammering effect, that worsens an already poor lubrication scenario.

 

Air-cooled engines run hotter than water cooled engines overall, and it's important to ensure cooling fins are perfectly clean and airflow isn't obstructed or reduced in any way.

 

 

[Ultralights]

Where do you get these?

http://www.wahltempplates.com/search-for-temp-plates/

or search ebay for temperature recorder labels.

 

$30 for a pack of 10

 

 

[rhtrudder]

Just ordered them, stuck on the outside of the oil tank should give an accurate measure of the operating temp of the oil , am I right in thinking this?

 

 

[Ultralights]

i use them as a confirmation, as someone mentioned before, they wont measure exact temps, but close, if you see a reading of say 130 deg c on the gauge, but check the hot side of the oil outlet and find it hasnt triggered an 70 deg spot, then you know it might be a guage issue. loose wire, corroded terminal, or something like that. also, the oil tank also acts as a giant cooler as well.

 

also with cooling airflow, look at the pressure difference between the front inlets and the air outlets at the bottom, some aircraft need a bigger lip at the bottom to reduce pressure behind it, which in turn, draws more air out of the engine bay, allowing more to come in. engine cooling air drag and aerodynamics is a dark art. some jabirus have a bigger lower lip added for the same reason.

 

 

another thing, standing air, has higher pressure, so an inlet on top of the cowling, in front of the windscreen might actually be pushing air into the area, not letting it out. thats the reason some race cars, and nascars have a bonnet scoop pointing backwards with the opening right near the windscreen.

 

maybe a relocation of the oil cooler might be needed, mine, in a savannah, mounted directly in front of the lip of the lower cowling exit, so there is a low pressure area created by the lip right behind the cooler, the radiator, in front of the oil cooler, and at the front of the engine cowl, has a huge high pressure are in front of it, so, the air flows easily, and fast, through both the oil and coolant coolers from the high side to the low side at the lower cowling.

 

i have never had a heating issue, only problems trying to keep it warm, even on a 40 deg day, my oil temps are normal. even in a sydney summer, part of my oil cooler is covered to keep temps up. and winter, its about 75% covered.

 

 

[rhtrudder]

That looks like a very neat set up , I have a mate with a Savannah and has trouble with high oil temps , could you take some more pictures so I can show him how you set yours up . The cowl scoop on my plane faces backwards so I figured the air flow over it would draw hot air out. We overcome cold running by fitting thermostats in the intake radiator line , works good.