The oil is disappearing from my 2001

[Circuit Dreaming]

Hello everyone, my 2001 Miata just recently had its engine rebuilt about 2,500 miles ago. When I assembled the rebuilt longblock back together I replaced all of the gaskets, the water pump, timing belt, accessory belts, ect. Everything was degreased, cleaned, and painted. The car really does run fantastic with a balanced crankshaft, 10lb flywheel, and 170-185 compression all across the board. What is concerning me is the car is burning lots of oil. I went to an automotive training course for ~6 hours on Saturday and put 220 miles on the car after driving 3 hours round trip, and driving probably 100 hard laps that day. When I got home my oil dipstick read just above the bottom mark . I checked all the fluids to be full before I left. Normally I could find what is wrong, but the car isn't putting out a puff of smoke, and my engine bay, oil pan, and subframe remain spotless still after installing the engine. I thought it could be the PVC valve, but I replaced that along with all the other wear items before I installed the engine. Any ideas where the oil could be going, or what could be the cause of it? I'm almost temped to call the builder, as they have a 12 month/12,000 miles warranty. I used 5w30 Mobil conventional so far, if that makes a difference.

Thanks for the help,

Nick

[— Phatmiata —]

I would call the builder up

[TNRooster3]

One of my miatas is also doing this, my brother-in-law is a mechanic and he says it could be a oil drain-back problem. Have you checked the oil after the car has been sitting a long time and the motor is cold? If you do check it cold and the oil is back up to normal on the dipstick it could be the drain-back holes are partly clogged up.

[— kung fu jesus —]

^that is a great lead. It happened to me with my wife's NB, though a '99. She checked the oil while refueling one day, told me it was a quart low, so I dumped in a quart without checking the dipstick. The car had already been sitting an hour. I check it after adding and it was a quart high.

Check your intake track, too. See if the exhaust side vent tube is dumping oil in there.

[Circuit Dreaming]

Thanks for the responses everyone. Wouldn't it be odd that the drain plugs is plugged since it's a new engine? I would think that kind of stuff would be cleaned when the engine was torn apart. I'll check it when I go racing again Saturday. What could clear the drain plugs? Seafoam?

[TNRooster3]

Well my Brother-in-law/ (mechanic for almost 50 years) says if you don't want to take the motor apart one old trick is to: "Pour a pint of diesel fuel into the oil filler, run the engine at fast idle for 30 minutes.
Drain the oil and put on a new oil filter, refill with a high detergent diesel oil.
After 500 miles drain the oil, replace the filter again and refill with the recommended oil."

[Rogue]

Sounds like the rings might not be seating….I'd take it to the builder like KFJ said.

[BoBo]

To the OP, there are many factors why the engine is consuming extra oil. Did you go through the break-in procedure so the rings can seat properly? Sometimes using break in oil helps the rings seat properly. Also did your engine builder use aftermarket piston rings that have less (piston ring tension) than OEM? In other words, did you request for the engine builder to build you a loose engine for performance purposes?

One last thing, did you have your valve guides replaced or at least added some liners or knurled? Was the valve seals replaced? as you probably know knurling is basically a "quick fix". A leak down test would really help you out. I know you mentioned that you replaced your PCV valve, but did you use OEM Mazda? sometimes cheap PCV valves are sold defective.

[Circuit Dreaming]

Thank you for the advice everyone! I do not know the specs of what was done during the rebuild, just that it was "a thorough longblock rebuild using quality oem replacement parts".

I changed the oil with mobile 1 synthetic last Monday with exactly 4 quarts. I drove it ~200 miles before Saturday morning where I checked the oil, where it read full multiple times. That morning I drove 1.5 hours to a race track and raced from 9am to about 12 almost non stop. After an hour lunch break I check my oil, and read full. Great! Then I do laps for another 3.5 hours. About 25 minutes after I'm done I check my oil before I drive home to find the oil level is just above the low mark! What? How could this be? I found a small leak on the valve cover gasket, but still no oil on the engine, ground, or smoke

Also on a side note I started to sme gas in the car when driving hard on the track. My gas cap isn't pressurized anymore, but I cannot find the leak. Any advice where to check?

[— kung fu jesus —]

Re: gas.

If you have an aftermarket exhaust, it is probably heating up the fuel tank. I have seen this a couple of times, under similar circumstances.

This is one solution:

http://www.thermotec.com/products/11...at-shield.html

[Circuit Dreaming]

Interesting. I don't have an aftermarket exhaust, but I do have an OEM Mazdaspeed Miata muffler. The reason I thought it could be a leak is because the gas pump won't stay on now after I started to smell the gas.

[— kung fu jesus —]

Hmmm. I would put that as top priority.