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-   Engine Performance (https://www.miataturbo.net/engine-performance-56/)
-   -   oil pressure on startup (https://www.miataturbo.net/engine-performance-56/oil-pressure-startup-93618/)

aidandj 06-21-2017 06:04 PM

hmmm. if the oil drainback valve is pre filter then the drainback valve wouldn't do anything for it.

AlwaysBroken 06-21-2017 06:42 PM

Huh? What do you mean? I thought the drainback valve was inside the filter? The stock filter inlet line goes directly to the inlet of my filter. After the filter it goes on to the thermostat/cooler/engine.

Engine filter orifice]----->[oil filter]---->[thermostat]------->[oil cooler]
Engine filter orifice]<---------------------[thermostat]<-------[oil cooler]

tetraruby 06-22-2017 12:44 AM

From my experience with oil filters, not all have equally well functioning internal check valves. Might want to take a shot at a different brand oil filter. A lot easier to try before dropping the frame. I've never noticed with my Miata, but have with some other vehicles / motors I've owned in the past that were sensitive to the how well the check valve / anti drain back valve worked. Maybe the amount of extra path you've added to the circuit is just enough to be noticeable? Might want to remove the oil cooler while you're at changing the filter out and see how things change?

AlwaysBroken 06-26-2017 01:09 AM

I did it this weekend. Supported the engine/trans with a crane, dropped the subframe, dropped the oil pan, installed a pickup gasket and then put it all back together again with AWR motor mounts.

Lessons learned:
  1. Subframe is much easier to drop than to reinstall afterwards. Holy shit. The subframe itself is probably pretty light but with brakes/suspension and steering attached it's heavy and unwieldy. With the legs of the crane under the car, it's cramped.
  2. Engine hoist plus one jack are all the tools you need to maneuver the subframe. Finding the right technique was a huge pain in the ass tho.
  3. Procedure I discovered for for subframe:
    1. Using the jack and some elbow grease, Install rearmost subframe bolts loosely because that's the easiest part to get to
    2. Jack up the center front of the subframe until you can align the motor mount studs
    3. Thread on the nuts to the motor mounts. Don't tighten all the way, just thread them on all the way
    4. Remove the bolts at the back of the subframe so it can move freely around the motor
    5. Release the subframe jack
    6. Jack up the subframe again slowly, align the front subframe studs with the holes in the subframe
    7. Jack it up all the way
    8. Put on the nuts to the front subframe bolts on both sides
    9. Put on the other bolts, tighten down the motor mounts, reinstall all the brake lines and suspension bits.
When I finish putting everything else back together I'll update about whether this fixes the startup pressure thing.

AlwaysBroken 06-30-2017 10:15 PM

PROTIP: the dipstick tube has a little tab on it with a threaded bit.... it has the strength of a cheap wire hanger and will bend if you look at it funny.

I just spend two fucking hours days trying to figure out what I had done to my oil pan to make the dipstick tube not seat right.... and there was nothing wrong with it. The tab that attaches it to the motor up top was bent a 1/4 of an inch. I bent it back and everything went together perfectly. FUUUUUUUUUUUUUUUU.

Also, I broke off the plastic tip of my dipstick again. Why the fuck isn't there an aftermarket metal version of the dipstick?

Bronson M 06-30-2017 10:25 PM


Originally Posted by AlwaysBroken (Post 1425164)

Also, I broke off the plastic tip of my dipstick again. Why the fuck isn't there an aftermarket metal version of the dipstick?

There it's actually, I've seen a few metal replacement handles behind pedaled on Facebook sale pages

albumleaf 07-01-2017 12:42 PM

Dipstick aside, any difference?

AlwaysBroken 07-01-2017 03:25 PM


Originally Posted by albumleaf (Post 1425231)
Dipstick aside, any difference?

Yes, m2cupcar was entirely correct. I left off the gasket, the seal wasn't perfect, it sucked air for the first 2 seconds whenever I started up.

So far, the first time I started after doing the gasket, it took like 2 seconds to pressurize everything (my filter is downhill from the thermostat/filter). I shut down, waited and started again... 50 psi oil pressure within half a second.

So in conclusion, that gasket is important, don't leave it out when you assemble your car. All glory and all cats to m2cupcar.


Originally Posted by m2cupcar (Post 1422197)
I have a very similar oiling setup (stock pump) and see full cold oil pressure (after sitting for a week) in about a second after the engine starts running (counting one one thousand two one thousand three one thousand). Did the builder install a gasket between the pickup flange and pump? I originally did not and had severely lagging oil pressure on cold start. Installed the gasket and it was fixed.


AlwaysBroken 07-03-2017 09:52 PM

Driven the car a few more times after letting it sit for over a day and on the initial startup, it still takes a couple of seconds to build full pressure (but it's like 1-2 seconds after sitting instead of 2-3 seconds every time). Subsequent startups under an hour apart seem to get instant pressure.

So I think the gasket is important but it looks like the extra post-filter volume of my oil cooler/thermo/lines is overwhelming the ability of the drainback valve in the filter over time. Or the oil pressure is escaping some other way. I'm going to continue switching filters at each oil change and see if I find one that gives the results I desire.


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