Hi RX8Club, I got my 8 about a month ago. It is a stock 09 GT with 46k miles. This is my second 8 so I decided to take care of the common problems one at the time. The first thing I did was coil, plug, wires. Unfortunately, I found some oil inside the intake tube and the box, there was a quarter-sized oil mark on the intake filter. I changed the filter, cleaned the box and tube. After I put everything back, I found there are lots of oil residuals outside of the upper extension manifold (not sure if this is the right name?) and the area around oil cap. Does this mean there is an oil leak somewhere or it is the aftermath of an excessive amount of oil inside the throttle body?




Oil build-up on the lower part of the upper manifold



There is no sign of power loss and rough idle, I do have some hissing noise from 3k-4k around the place where upper extension manifold is. Any idea of what might be the cause? Thanks

 

Oil on the upper intake manifold usually means that somebody spilled oil during an oil change.

Oil in the airbox and accordion tube is probably from overfilling.

 

Thanks for the input, I am aware of the overfilling issue for the 8. I guess there is a chance that the Mazda dealer spilled oil during the previous oil change, but I just can't imagine how could someone spill this much oil w/o cleaning it. It made me think something went wrong during the last oil change, and the oil spilled all over the engine bay, they cleaned it a little bit and put the engine cover on the car hope that the owner did not find out.

 

Oil as pictured definitely looks like spillage from oil filling. For a car that requires frequent oil adding they could not have put the filler any further back in the engine bay. Even with a funnel it is a stretch. There is a slight possibility it is a bad seal on the filler cap.

 

Great insight! I checked the records from the previous owner, the dealer used S1 oil filter on last oil change. I just ordered few S2 filters and will do oil changes myself from now on.

 

I've been wondering the same thing. I have that oil residue in those 2 same exact places. and i get like a light metallic scraping/hissing sound from 5k to 6k which again can not find a solution for. My theory is that there is a leak somewhere that I can't visibly dripping very slowly on to the exhaust manifold and cooking off that oil and it then settles on the plastic, but that isn't plausible since the residue is only apparent in those 2 places

 

I thought the hissing is caused by the excessive amount of oil inside the manifold. But I have not experienced any CELs and the car drives fine so I assume it is caused by overfill. The hissing sound on my car is like the sound of wind noise, it is gone (or covered by engine noise) after 4k.

 

The SSV, VDI and VFAD are all vacuum actuated. Since the VDI valve should be closed until 7250 RPM, you should probably look at the vacuum lines for the SSV (opens at 3750) and VFAD (opens at 5500). The APV opens at 6000 but isn't vacuum operated. (All of these RPM values assume you are under load.)

The fact that it goes away after 6k RPM could just be the fact that the engine noise drowns it out.

An audible vacuum leak should be obvious when looking at fuel trims. If you don't have an Bluetooth OBD-II adapter and smartphone app, get one and log MAF rate, AFR/Lambda and long term fuel trims as to wind it out to redline.

Or, you could just be hearing things.

I can't think of a way that oil in the UIM or LIM would cause any noise audible from inside the cabin. For the most part, it will just sit there in the intake, (very) slowly being pulled into the engine. Some may leak forward onto the filter.

 

Is the induction noise from the intake particularly loud during 3k-4k rpm?

 

Not unless you have an aftermarket intake or the VFAD is stuck open.

 

I made a video after work. The hissing sound happens from 3k-5k. One thing I noticed was the sound will "come back" when I let off the throttle, in the exact same rpm range. Is this the sound of VFAD?

https://www.youtube.com/watch?v=t28K...ature=youtu.be

 

I figured the sound is not obvious in open area so I did a recording in the garage. I might be paranoid about sound but the sound of the engine change to a hissing noise after 3000 rpm. One thing I need to mention is I just installed MeganRacing motor mounts, I do not know if solid engine mounts would give more noisy engine or not. Any inputs would be greatly appreciated!

 

I don't know if the VFAD will open if the engine isn't under. I'm pretty certain I read somewhere that the SSV, VDI and APV won't open simply by rev'ing it while stationary.

I don't have the best ear for induction noises so I'll let others chime in.