Oil temperature gauge problems

[bluebus86]

I found the sump read via the dip stick hole in my 1600 Dp motor reads the same temperature as the reading from the stock oil pressure sendor location.
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[cbath]

Ahh, I see. well I have two oil sump sending units which wont fit that thread. I do have a lathe and am pretty good at cutting threads. Have you ever heard of anyone making a 14mm-18mm threaded insert adapter so they could use the drain plug sender in the relief valve spot.

I suppose it is worth a shot, whats the worst that could happen, if I scrap one of my spare senders, no big deal.

[cbath]

any tricks for removing the relief valve plug? that sucker is in there tight and its just one of those crappy flat head slots.

[cbath]

Anyone out there think this adapter I made to make my oil sump sender fit the oil relief valve opening will work. The tolerances were pretty tight so I am just a little worried about snapping it off if I over tighten the bolt.

[cbath]

I was also thinking of maybe soldering the two pieces together since I have room on the topside to do so. I don't know enough about how the senders are made to know if this could damage the sender though.

[cbath]

Just wanted to follow up on this thread and let you know how things worked out.

The adapter I made to install the oil pump sender in the oil relief valve location works perfectly, there are no leaks and I was able to maintain the the same depth of thread so the spring tension on the relief valve spring should be exactly the same.

As for how it works? It is reading much better now. It is reading about 25 degrees higher under the same driving conditions as when it was in the sump, which I believe to be a much more accurate reading.

Makes me wonder why they continue to sell the oil sump senders when it really does seem to be a poor location for the sensor.

anyway, thanks for all the help, problem solved.

[Wayne S. Johnson]

[cbath]

Wayne, are you saying that placing the sender in the pressure relief valve location reads higher simply because it is actually threaded into the case, which is warmer in general due to its proximity to the cylinders.

That is apposed to the oil sump cover plate which tends to be a much cooler spot on the engine because it is both farthest from the cylinders and is also made of less heat conductive steel?

Anyone who does machine work knows oil make for a terrible coolant,but I I guess even if true, non of these factors really matters so long as the temperature being conveyed through the sender provides some sort of accurate corollary to the actual oil temperature, even if it is a little off due to other factors. The question is which one is more accurate.

I actually have both of my senders installed at the moment, the new one in the pressure relief valve, and the old one in the oil sump plug (mostly because I don't have a replacement plug at the moment) I can actually just switch the wire on the fly to measure the difference between the two, so when I get some time, I can do a thermometer down the dipstick, as well as take a read off of both locations to see what looks best. I will have to check that out very soon.

[Wayne S. Johnson]

[DrKeck]

I wanted to revive this thread to ask some questions in order to better understand what these people are talking about. I was thinking about installing both an oil temp and pressure gauge in a couple month after i finish more important things on my daily driver. I had a question about why people recommend the oil relief value location over the sump location for temp?

- Is it simple because this is the most accurate location? Could you just put one on the sump and use the the oil dip stick to see how far off you gauge is and just note the correction? What i mean is say, your sump is 40 degrees off from the dip stick temp, so just note this when you see it change, just add 40 degrees to the gauge? Or is the sump temp just completely inaccurate all together and you really would have no idea what the temp is because of its location and the fact that it will vary with the ambient air as mentioned in this post?

-seconds is, if i install a VDO oil pressure sender (SO i can see the pressure and still use my dumb light) in place of the oil pressure switch, will it give me an accurate reading for pressure or is this also false data, i was confused about that subject in this post as well?

- lastly, While i know there will always be variations in accuracy in the Temp gauges, if you did have the gauges installed and ACTUALLY monitored it daily. If you noticed a large change in either temp or pressure it would clue you into what was going on, wouldn't it? even if they are not the exact temp or pressure they should still be at a constant for those gauges dependent on driving conditions and the constant would make it easy to see changes?

what i mean is, say you gauges read 30 PSI and a temp of 170F, and you verified that the temp of your engine is within limited according to your manual through the dipstick method. couldn't you used the gauges this way and if you see the pressure rise to 50 PSI on a random day when it shouldn't change that much for the condition, then you know there is a problem with your pressure of conversely, if you noticed you temp rise to 240 F one day then you know its over heating the oil? while the values of the gauges wouldn't be accurate the change itself would mean a problem? of am i way off base with what I'm talking about?

Sorry for the long post but i have been reading a bunch of posts about this topic lately an I'm just trying iron down what I'm thinking so i revived this post to ask my questions?
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[cbath]

After testing both locations on my car, I felt like the relief valve location was more accurate, although nothing is perfect.

The sender in the sump was problematic for a couple reasons. Not only did it read low, but the sensor was long enough that it actually rammed up into the oil screen rivet, so much so that I had to shim the sensor out with washers and bend the screen, which was not very desirable.

As far as your question on accuracy, I think close is the best you will ever do, so yes, figuring out what is normal for your car and looking for changes is the smartest approach in my book.

My oil pressure sender is T'd off of my dumby light like a lot of folks do, and it seems to work very well while keeping the dumby light intact.

Good luck.

[DrKeck]

[Eric&Barb]

Pretty sure cbath means T fitting for both senders.

For us, have tested temp sender machined in same T-fitting, so can run all three senders in one. Verified with a dipstick temp sender to read same temp.

Dual oil pressure gauge sender that has idiot light sender built in seem to have lots of reports of slow to light up if pressure drops off too much.
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[DrKeck]

thanks for the information, i never would never have thought about that type of splitting. i will keep it in mind when i order the parts for my pressure gauge. thanks for all the input on this discussion.
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1966 Beetle
1600cc 50bhp
Daily Driver

[Eric&Barb]

No problem. Next engine will probably go with a sender in the oil filter pump and see how that does.

Have used this vintage 70s type that has the plug on the left side.

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[cbath]

Yes, what Eric&Barb posted is my set up.