Oil, Fluids, and Gauges, Oh My

[Digitalwave]

This summer I set up a new chassis for HPDE use, and have been working out some bugs over the last month or so. Yesterday I did my first track day with it, and now have some more bugs to work out.

Car: 318iS slick top with an M20 swap and E30 M3 5-lug
Motor: M20B25 with a solid refresh (gaskets, wear items, all internals stock)
Mods: Intake, Injectors, Full Exhaust
Fluids: Castrol GTX 20w50 engine, Redline MTL in tranny
Gauges: Innovate MTX-D oil temperature and oil pressure, coolant temperature, MTX-L wide band
Locations: Water temp is tapped to the top of the thermostat housing next to the stock water temp senders. I am not running an oil cooler so I deleted the oil filter elbow and it is mounted directly to the block. In between the filter is an aluminum Mishimoto sandwich plate. The oil temperature thermistor is mounted directly to the sandwich plate, and the oil pressure sender is remotely mounted off the sandwich plate via a braided line to the frame rail to isolate it from vibration.

Shortly after getting the swap up and running I noticed I'm leaking a little fluid from the tranny bellhousing. I checked and I had overfilled the tranny, so I figured that solved the issue. That wasn't it, and it has gotten worse, but I'll get to that again. The gauges seemed to be functioning and reading properly after I got them all wired up. Coolant temp is about 185-198 max when idling with my SPAL puller fan. Oil pressure was about 75psi at start up idle, then would be around 30psi idle when warm and around 60-80psi while driving around and going WOT. All seemed pretty normal (if not a little bit high compared to others idling at ~15-20psi).

On the bizarre side, oil temp was always really high. It would get up to 220-230* F just driving around the street for 15 minutes, not even getting on it. According to this thread, Ranger was having the same issues with ridiculously high indicated temperatures when using an aluminum sandwich plate.

Fast forward to the track day. 5 laps in and my oil temperature is maxed out on the gauge at 280*, while coolant temps stayed at 190-195*. I think I need to relocate the thermistor to either the oil pan (popular on SpecE30s) or use an adapter (because my thermistor is 1/8 NPT) and thread it in where the dummy light switch is on the side of the block, like nando did. There is no way my oil temps are that high on a stock M20. I think that my thermistor and/or sandwich plate is getting heat soaked, especially being right next to the headers.

Now on to oil pressure. My baffled oil pan did admirably and my lowest oil pressure during our long left handed sweeper was about 20psi. It was solid 60-70psi everywhere else on the track. HOWEVER, by the end of the track day I had noticed my oil pressure had gone up a good 15psi all the way across the board. My previous 30psi idle was now 45-50psi. Cruising and WOT is now 80-100psi. Water temps went up slightly to 205*, but I had a passenger then and it was the hottest session of the day.

On top of all that, my leak from the bellhousing got a lot worse. Since the tranny oil is brand new (pink) Redline MTL, and the oil dripping out is very dirty, I think it might actually be engine oil from the rear main seal, especially because I did go through about 1/2qt of oil during the track day. In my last session my clutch started slipping some, probably because it got some oil on it from the leak.

So, after that backstory, here are my mysteries:

1. Why is my oil temp indicating so high? Should I try the stock oil switch location on the block next?
2. Why did my oil pressure magically increase during/after the track day? Is 20w50 too thick for track use? Did I blow my HG, and the cooling system is pressurizing the oil system further? (there is no oil in the coolant, but it could be vice versa)
3. Could the high oil pressure be contributing to the bellhousing leak?
4. Could the bellhouse leak have gotten on the clutch surface causing the slip? I came off the track when it got noticeable. I should be able to clean up the clutch and flywheel and reinstall them without replacing and resurfacing, right? It's a ClutchMasters FX400 on a lightened stock flywheel.

[peterman]

I am not running an oil cooler so I deleted the oil filter elbow and it is mounted directly to the block. In between the filter is an aluminum Mishimoto sandwich plate. The oil temperature thermistor is mounted directly to the sandwich plate, and the oil pressure sender is remotely mounted off the sandwich plate via a braided line to the frame rail to isolate it from vibration.

There is a reason BMW put an oil cooler on the M20s.

The AL sandwich plate will conduct a lot of heat to that brass temp sensor. A lot of people will tell you that the most accurate oil temps can be read at the surface of the oil in the pan as that is where it would be measurably the hottest outside of the bearing surfaces they are cooling/lubing.
That being said, I run my temp sensor in the banjo bolt in the oil filter/oil Tstat housing and see 200-210°F on the freeway and about 220-230°F on track

Is the engine oil burnt? If its getting black and dirty that quickly you do in fact have high oil temps and something is quite wrong.

[digger]

There is a relief valve in the block that kicks in at about 70psi or there abouts so if you are getting 100psi numbers either that isn’t working or the gauge/sensor is faulty. xxW-50 is not too thick for the track if youre seeing 200f +.

[Digitalwave]

There is a reason BMW put an oil cooler on the M20s.

The AL sandwich plate will conduct a lot of heat to that brass temp sensor. A lot of people will tell you that the most accurate oil temps can be read at the surface of the oil in the pan as that is where it would be measurably the hottest outside of the bearing surfaces they are cooling/lubing.
That being said, I run my temp sensor in the banjo bolt in the oil filter/oil Tstat housing and see 200-210°F on the freeway and about 220-230°F on track

Is the engine oil burnt? If its getting black and dirty that quickly you do in fact have high oil temps and something is quite wrong.

Regarding the oil cooler, I am torn on the issue. Most of my research shows that just about no E30 race cars run an oil cooler. That includes the endurance racers running running 6-12 hour races. One plus side is the added oil capacity, but if the oil thermostat is not even opening, is that really a benefit? It seems pretty agreed upon that the stock oil cooler is only good for about a 5* difference, which wouldn't change much in my situation. Even a good aftermarket cooler may only be good for 10-15*.

That thread I linked to on the Spec E30 forums, the guy was running 4 different oil temp sensors on his motor simulatenously, and found the aluminum sandwich plate was reading 90* hotter than a sensor in the oil pan on the same car. So I am either seriously heat soaking the thermistor, or my motor is living on borrowed time ;D I don't necessarily think the location near the filter is bad (lots of people use the banjo bolt), but it might be the aluminum sandwich plate itself that is the real issue.

I do think regardless of the sensor being an issue or not that I may have cooked this dino oil. It's hard to tell when wiping some of the dripped oil from the bellhousing off the ground.

There is a relief valve in the block that kicks in at about 70psi or there abouts so if you are getting 100psi numbers either that isn’t working or the gauge/sensor is faulty. xxW-50 is not too thick for the track if youre seeing 200f +.

It's definitely a strange issue. I verified on my GoPro videos that the car was idling at 30psi and on the track was getting up to a max of 75-80psi (near redline, with the oil up to temp) in the first two sessions. By the third session is was over 90psi under the same conditions.

It's hard to find info on those symptoms because my searches are all coming up with results related to the OPPOSITE condition, of the oil pressure being too low during or after a track day. Oil pressure relief valve problems seem to usually cause low pressure, not high. In fact a lot of SpecE30 guys are plugging their reliefs to keep pressures up.

[digger]

id say gauge is wrong, independently verify pressure with different tester if you can.

if your oil really was 280F there is no way youre pressures would be that high.

if youre giving it some stick then the sump temp gauge is fine as the oil gets circulated reasonably quickly when youre doing rpm so does not cool off as much sitting in the pan.

i would expect the oil temp to be higher than coolant on the track

[nando]

Yeah definitely having it in an aluminum sandwich block is probably not good.

I have my temp sensor in the oil pressure switch location. I don't think I even needed an adapter - it was the same thread as the original switch. My pressure sender has it's own pressure switch signal, and the original switch leaked anyway, so swapping it out was a no-brainer.

I had it on the pan for a while too. I'm conflicted there. I feel like I get a more reliable reading in the pressure switch location - remember that the pan also functions to cool the oil. It would consistently read lower in the pan than what seemed realistic. I mean, after driving for an hour, it might break 200 degrees (but usually not).

Maybe it works on a car that is only driven on the track, the oil in the pan might increase in temp faster. But the block seems like a better place, because that oil is in service actually lubricating your engine, and that is the oil that I'd like to know the temperature of.

[TobyB]

just about no E30 race cars run an oil cooler

Most of the Pro3 cars run the stock one.

t

[Digitalwave]

I am going to try the temperature thermistor in the stock switch location in the block next. I already ordered an M12x1.5 to 1/8 NPT adapter for that. I don't want to drill my oil pan if I don't have to.

My pressure switch is remote mounted off the sandwich plate and a 1' braided line, so I'm going to retain the sandwich plate for that.

The only real mystery at this point is why my oil pressure went up by the end of the track day. Only thing I can really think of is my oil has a major issue or the bypass on my filter isn't working. Something of that nature. It seems like everyone that is having issues with oil relief valve are getting low pressures, not high.

If I can get accurate temp readings and I need the oil cooler, I still have the system I can reinstall. But if it's only good for 5* or so (and James Crivellone said his never opens during races), then I may not add it back.

[peterman]

If you did not bleed the remote line, you could have an air bubble in it causing bad pressure readings. It will obviously gain pressure as temps rise... but it should never be over the relief valve pressure. I put my pressure sender at the stock idiot light location

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[Digitalwave]

I did not think of that. What's the proper way to bleed that line? Run the motor with the line lower than the motor so the air rises?

Does the oil filter and sandwich plate even stay filled with oil when the motor is off? Wouldn't air get back in the line?

On the same note: is there an ideal direction for mounting the oil pressure sender? Right now I have mine mounted vertically, with the wiring on the top, and the line/inlet on the bottom pointed downwards.

[TobyB]

an air bubble in it causing bad pressure readings.

Nope, air won't affect pressure readings.
An air bubble MIGHT cause slow response, but pressure is pressure-
the oil will eventually compress the air to whatever pressure the oil is at.
Otherwise, you have what's commonly known as 'a leak'.

t

[peterman]

I would crack the line open just a bit witht the engine on, just like you are bleeding the coolant. Once thers oil in the line it shouldnt drain. Simialr to putting your finger on a straw after you dunk it in a glass of water. I don't think there is an ideal direction. My brother has a gauge in his nova that has an oil lone straight into the cabin.
How long does it take for the pressure to build/idiot light to go off when you start the car? If its immediate, then you are holding pressure well. Check what the resisetance profile of the sender is. If the wire is pinched or there is a loose connection then you could have a false reading. I would check all wiring first.


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[george graves]

Nope, air won't affect pressure readings.
An air bubble MIGHT cause slow response, but pressure is pressure-
the oil will eventually compress the air to whatever pressure the oil is at.
Otherwise, you have what's commonly known as 'a leak'.

t

Toby is right.

[Digitalwave]

I have not touched the car yet. However, it has dawned on me that there might be an issue with my Innovate MTX-D oil pressure and oil temperature dual function gauge. When I turn the gauge , it's reading 11-12psi of oil pressure when the motor is off, and that should not be the case. I had an issue with the MTX-L wideband gauge as well that was already warrantied. Maybe it's time to switch to AEM or Defi.

On a side note: anyone know if I will be able to clean off and re-use my ceramic Clutchmaster FX400 clutch after it got oil on it? I know you can't reuse an organic clutch that got oil on it, but I am hoping ceramic is another case.

[Digitalwave]

Just to update this thread: I changed my oil last weekend and it looked like a glitter bomb. It seems that the added oil pressure was from all the shavings in the oil. I am also guessing that the oil temps were actually incredibly high because the oil was clearly cooked. I guess the rod bearing(s) or whatever is shot inside was probably heating up the oil bad.

Back to the drawing board!