Oil from Blow Off Valve - Any Ideas?
 

Hi Guys,

I had my 02 FMII Miata on the track a couple weeks ago and ran into something interesting/disturbing.

The turbo would creep up to 15 psi in 4th and 5th gear where the blow off value would give a pop and then the turbo would go back to the 10psi it is set to. I do not like the turbo creep, but that is not the disturbing part. The blow off value seems to be spraying a squirt of oil when it opens. When I finished the track sessions, there would be a fine layer of oil on the inner liner of the hood that is just above the blow off value.

2 Questions:

1. Does anyone have any recommendations of how to prevent the turbo creep. It does not do it in the lower gears. It only happens when I'm going all out on the track in 4th and 5th gears.

2. I imagine that the oil mist is bad news about something, but I don't know what. Does anyone have any ideas?

Thank you,

Greg

Wow...sounds like bad things.

Boost creep issues are usually wastegate related, not BOV.

You'd have to elaborate on the oil stream/mist issue...I'm not understanding. What made you notice it...any pics?

I noticed the oil mist in between track sessions when I would raise the hood to let the car cool off. There was oil on the inner liner of the hood, but no where else. It wasn't even enough to be dripping down. The first time, I just cleaned it up and had no idea where it was coming from. Oil level was not down. After the next track session, it was there again. The only issue I was having on the track was the blow off value opening in 4th and 5th gears. The oil mist was directly directly above the Blow off value and the blow off value opening was oily. I concluded that was where it is coming from.

Unfortunately, I do not have any pictures..

Greg

Oh ok...now it makes sense.

You're getting oil in your intake tract...a bad sign for the turbo.

I still have no idea how your BOV is opening when you're at full boost. If properly plumbed up it should only open when it sees vacuum.

There are really two things that will cause the BOV to expell oil.

1) If you have the breather line from the VC plummed into th eintake tract. On all cars with this, you'll get some oil into the intake which is normal. Over a long time, you may build up enough to get it all the way through the intercooler and enough to start coming out of the BOV. If you have any blow-by or a bad PCV valve, the situation will be exacerbated. You can do a quick check for blow-by by pulling the dipstick while the car is running. and if you see a noticable amount of vapor being blown out of the dipstick.

2) Oil seals in turbo are letting go and allowing oil to seep into the compressor housing.

Either way, I'd suggest pulling the entire intake apart and cleaning it up and seeing how much oil is in the intake tract. Another good preventative measure is to hook up the PCV and breather to a catch can to help reduce the amount of oil vapor in the intake.

Thank you very much for your advice. My mechanic is taking a peak at the car tomorrow and I will print this out for him to follow. Unfortunately, it is way above my ability.

i'm betting its breather line related. mine was making a mess until i vented it to atmosphere. now the pipes are clean and dry :)

Can you tell me a bit about how to vent it to atmosphere?

Thank you,

Greg

You have a standalone right? Just take the hose off. Some people put a little filter on the BOV. Plug up the hole in the intake.

what are you using for boost control? depending on that you are under higher load in 4th and 5th so it tends to boost higher in those gears depending on how good your bcs is.

Send me your turbo, my guys will port the turbine housing for you. Or, if you are using an electronic boost control solenoid - take it off and go with actuator control only. Boost creep with solenoids is very common, even on a ported turbo.
Stephanie

If you have steel intercooler tubes, having some oil in the tubing is a good thing. Seeping thru turbo hose is not a good thing.

OP - if you have not done a compression test and/or leak down test lately, now might be a good time. :)
Stephanie

It is a manual boost controller. I do not know what brand. It was originally an electronic boost controller, which did not work well at all. This one worked fine for two previous track days. Is there one you recommend?

Please excuse my ignorance, but what do you mean by actuator control only?

Thank you.

She means that you should just run wastegate boost and not the controller.

I have a similar problem with excessive oil getting in my intake and ending up on the top of my hood and near the outlet of the blow off valve. I also get a blue smoke cloud at cold starts. The gt25r turbo was just dropped off with ATP today. At this point it's worth the $50 fee if I'm wrong and the turbo is in good shape. A lot of what I did to convince myself it's probably the turbo was already mentioned:

- compression test (my engine looks good)
- put filter on valve cover breather port so oil can't get into the compressor housing from there and check PCV (my filter and surrounding area is dry and PCV is good)
- add restrictor. this helped the blue smoke problem initially, but the smoke just came back 3 weeks later.
- check drain line for smooth transitions and no blockage.

Most of the oil was at the compressor outlet and was soaking the coupler enough where oil was running down the outside of the hotside pipes and dripping onto the ground. Anything near the compressor outlet and blow off valve was getting covered in oil.

sounds like you need new rings AND valve seals.

I must be missing how oil is getting from the engine to the compressor. The valve cover isn't connected to the intake elbow. It's vented to atmosphere and the filter is dry.

If the oil seals inside the turbo are compromised, it will leak oil into the compressor and will get blown into the intake piping, same with the exhaust, oil will get into the hot exhaust turbine and burn up. But if you're getting smoke on start up (turbo is too cold to burn oil for the first few minutes), I'd suspect valve seals allowing oil to build up after the car has been running and that oil burns on start up resulting in smoke.