DIY:K thermocouples tell engine temperature

[motoman]

Ever wonder how hot your sump oil or head(s) are? Maybe you should unless you're content with the short life predicted for air cooled tractors. A useful technology widely used in industry is the "K" type thermocouple. Sounds too technical? It's self powered , very accurate, and cheap (for DIY'ers). You can make an oil probe (stick it down the dipstick tube), and a cylinder head sensor (put it under the sparkplug) from the two lead K wire. Just made them and they work. Cost, $ 12.

Oh yeah... you need a digital thermometer, roughly the size of VOM (meter). Don't turn away yet. Mine is 8 years ok, cost $29. Ebay has them for $49. American made are more $.

Thermometers are not suitable for permanent mounting on the tractor. Instead, you will take periodic readings prompted by curiosity or as backup for existing gauges. Sorry for cracking the $50 DIY barrier. Tell me if you are interested and I will post two threads... with pics. :drink:

 

[DaveTN]

Yeah, sounds very interesting, show us your pix.

Give me a little more info on what you meant by putting it "under the sparkplug" please.

Thanks. Dave

 

[panabiker]

I like wireless so I use infrared thermometers. No wiring, no touching. They cost around $30 and up. The more important question is what is the "normal" temperature range for various parts and what to do if it exceeds the range.

 

[motoman]

Dave , For years VW bug and especially van owners have blown engines with regularity. The major problem was head over temp. They often install a head temp gage which is essentially a spark plug gasket with a wire to a heat gage. This approach is used in small aircraft, motorcycles, go- carts and race cars. Some have proven widely inaccurate. The K appoach remedies the inaccuracy. I will post some pics. Motoman

 

[motoman]

Panabiker, I see that the infra red units are coming down in price. I do not have one ,but how , for instance ,can you get "no fin" head readings ? Also, how can you get sump oil temp? Anyway I believe we know what the dangerous range is for aluminum heads from a vast literatue on line . I am tring to run a series of sump oil vs head temps, but that will probably not complete untill I stress my Craftsman Intek with worst case which is Spring ,3 bagigng ,on slope with damp grass. Meanwhile leaf bagging is coming up and I may be able to throw out some numbers. Motoman

 

[SeniorCitizen]

Because of curiosity only, I once screwed a dial thermometer with a 3" stem directly into the oil drain on a 12 hp briggs riding mower and the highest oil temp. recorded was around 250 F with the ambient temperature 95.

Unless there is a temperature shut down or audible warning set at a predetermined value I see no purpose since we can't mow and continually watch a temperature gauge or oil pressure gauge etc.

Constantly monitoring gauges would be similar to texting. :laughing:

 

[panabiker]

Unless there is a temperature shut down or audible warning set at a predetermined value I see no purpose since we can't mow and continually watch a temperature gauge or oil pressure gauge etc.

Constantly monitoring gauges would be similar to texting. :laughing:

Indeed. If an engine overheats regularly in a non-abusive use, it's more indicative of some design flaw. Maybe a larger engine should have been installed on the mower.

 

[motoman]

Well Sandbur and Panabiker. I only have experience with my once ever Craftsman 48" Intek. After reading these threads for over a year I know there are better disigns out there. But what's worked for me after two self destructions is exactly monitoring an oil temp gauge, especially when I use the tractor as designed-cutting grass with a 3 bagger on a slight grade.

I have read that some better tractors have red warning lights for oil level, but not that I can recall for oil or head temp. Incidentally there's some indication of at least a plus 75F at the head over oil temp
on my unit. If that's true your reading suggests the head was entering a dangerous region. I'm just trying to set some guide lines. Of course only a lunatic fringe would pursue such an effort. :tractor:

 

[Ariena]

Dave , For years VW bug and especially van owners Motoman

I know this from personal experience. I solved this by 2 methods.
#1. Oil temperature sensor installed through the dipstick tube.
#2. Oil temperature sensor installed in the oil pan drain. The sensor screws into the pan instead of your drain plug.
I realize that this does not give you head temperature, but it puts you in the Ballpark!

 

[motoman]

Ariena, WIll you take my tractor and some cash for your buug? Hope it's not a garage queen.

Please tell us what ballpark sump oil temp you avoid and how you cool down if that temp is reached.....Motoman