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Miata Turbo Forum - Boost cars, acquire cats. (https://www.miataturbo.net/)
-   Engine Performance (https://www.miataturbo.net/engine-performance-56/)
-   -   I don't trust my oil temp gauge (https://www.miataturbo.net/engine-performance-56/i-dont-trust-my-oil-temp-gauge-86358/)

patsmx5 10-22-2015 11:19 PM
Originally Posted by pcormier66 (Post 1277710)
Good idea Rick. I'm planning an oil change soon and will remove the sensor and dip in boiling water. Here is the best pic I could get of the sensor location. It is the black wire connected to the brass fitting on the block next to where the OEM oil filter was located before it was rerouted to the firewall. Looks like the original owner inserted a "y" fitting between the block and the OEM oil pressure sensor and inserted the AIM temp sensor in the other end of the "Y". The orientation of the pic is not accurate. Best I could do with my big hands and an iPhone. Seems like a good place to get accurate temp readings? What do you think?
That is useless, there is no oil flow in that area. No wonder it reads so low and off. It needs to be installed in the pan ideally, or second best, in a fitting that has oil being pumped across it constantly so as the temp of the oil changes, the sensor can pick that up immediately. And of course, before the oil cooler. Goal is to measure how HOT the oil got. Best place to mount the sensor would be on the rod or main bearings. But that's extremely difficult to do, so oil pan is second best and 1000x more practical.

pcormier66 10-22-2015 11:29 PM
Originally Posted by patsmx5 (Post 1277713)
That is useless, there is no oil flow in that area. No wonder it reads so low and off. It needs to be installed in the pan ideally, or second best, in a fitting that has oil being pumped across it constantly so as the temp of the oil changes, the sensor can pick that up immediately. And of course, before the oil cooler. Goal is to measure how HOT the oil got. Best place to mount the sensor would be on the rod or main bearings. But that's extremely difficult to do, so oil pan is second best and 1000x more practical.
I knew this smelled like a fish from the head back. Sounds like the original owner didn't want to drill any holes. It's not the original block. It was an easy install with the motor out. But why cheat yourself? Mechanic probably told him it was plumbed somewhere else. I'll still test the sensor in boiling water to ensure it's good. Then reinstall in a better location. Thanks for helping me troubleshoot.

Philip

patsmx5 10-22-2015 11:34 PM
No problem, glad you figured this out.

Joe Perez 10-22-2015 11:37 PM
Originally Posted by pcormier66 (Post 1277716)
I'll still test the sensor in boiling water to ensure it's good. Then reinstall in a better location. Thanks for helping me troubleshoot.
I'm not even sure I'd bother; you found the problem.

Stick that sensor into a sandwich plate located between the engine block and the stock heat exchanger (if still present), and in a location which places it *before* any type of oil cooler.

If uncertain, oil goes into the filter through the small holes around the outside, and comes out of the filter through the large hole in the middle. Situate sensor accordingly.

pcormier66 03-03-2016 01:34 PM
Update: Installed a brand new sensor in the oil pan. Also installed coolant reroute kit and boxed in the radiator. Water temps are a little lower. Oil temp is about 15-20 degrees higher than before. Now oil hot at about 215. Oil temps would probably be a little higher if not for improved water cooling. Still seems a tad low but I'm not complaining. Thanks for all the advice.

Joe Perez 03-03-2016 02:55 PM
215° as measured at the pan ain't horrible. The oil in the pan is going to be slightly cooler than peak temp simply because the pan itself is a heat sink.

aidandj 03-03-2016 05:33 PM
Late to the party, but would that sensor location really stay cooler than the others. Its still in direct contact with oil, and I could see it not being as responsive, but I don't see the oil staying at a significantly lower temperature. Isn't that port connected to the main flow of oil to the head?

hornetball 03-03-2016 05:40 PM
Originally Posted by aidandj (Post 1313039)
Late to the party, but would that sensor location really stay cooler than the others. Its still in direct contact with oil, and I could see it not being as responsive, but I don't see the oil staying at a significantly lower temperature. Isn't that port connected to the main flow of oil to the head?
Phil's running an oil cooler. That location is post-cooler.

aidandj 03-03-2016 05:45 PM
I know, I just finished installing a sensor there to get pre and post cooler data. Just wondering about the posts above about having little flow in the area.

pcormier66 03-03-2016 05:55 PM
I suppose the empirical answer is 15-20 degrees cooler in that spot as opposed to the oil pan.

aidandj 03-03-2016 06:13 PM
Originally Posted by pcormier66 (Post 1313049)
I suppose the empirical answer is 15-20 degrees cooler in that spot as opposed to the oil pan.
Interesting. Wonder if the pan oil is hotter than the oil going to the head. Wonder what that Delta would be without an oil cooler.

pcormier66 03-03-2016 10:01 PM
The problem with the sensor on mine is that it is not actually in the block. It's on the end of a "Y" fitting outside the block. It is not getting much fresh oil flow. I think you would be fine if the sensor is actually exposed to the interior engine cavity.

aidandj 03-03-2016 10:07 PM
But its still engine oil, in direct contact with engine oil, and oil flowing by the hole. Heat transfer and just flow will heat up the oil in the adapter.

pcormier66 03-03-2016 10:14 PM
I'm no expert. That's why I started the thread. But numbers don't lie. Unless of course the sensor in that spot was defective. Which is entirely possible with my luck considering the number of issues I've had in general.

greeenteeee 03-04-2016 01:46 PM
Originally Posted by pcormier66 (Post 1313087)
I'm no expert. That's why I started the thread. But numbers don't lie. Unless of course the sensor in that spot was defective. Which is entirely possible with my luck considering the number of issues I've had in general.
Just to add a data point, I just got the oil temp sender and gauge from my old NA installed. Using a sandwich, with OT sender AT the adaptor itself. Oil gets up to temp pretty quickly (compared to my old 1.6L)-- the Oil warmer is working. I reach about 200 degrees in recent 70* ambients, and it only reaches up to 215 or so while idling or in heavy traffic.

aidandj 03-04-2016 01:47 PM
Oil temp wont change much when idling. You need high RPM to get oil temp to go up.

greeenteeee 03-04-2016 02:05 PM
Originally Posted by aidandj (Post 1313277)
Oil temp wont change much when idling. You need high RPM to get oil temp to go up.
It does change in this case, and it does in fact climb to ~215 from idling vs ~200 in street use in 70* ambient. It always drops once the car gets going.

And yes, I don't expect it to reach very high temps in street use My old 1.6L only reaches 260* easily in a 20 minute session on track on a 90* ambient day but never got past 200* in Cali ambient temps.

aidandj 03-04-2016 02:06 PM
Thats why I said it wont change much...15* is not a lot.

Leafy 03-04-2016 08:38 PM
If you dont trust your sensor why not test the fucking thing directly? Unscrew that fucker from the engine and drop it in some boiling water if the gauge reads around 212°F then the gauge is right or at least close enough for the temp range you'll be using it in.

*Edit I missed a bunch of posts.


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