Dirty Oil

[slamdagin]

I've got a new GP2180 and am trying to diagnose multiple problems during the 10 hour break in period with the engine oil. The metal seems to be decreasing and I've change the oil six times now to try to mitigate the impact of grit being pumped through the engine. Steve Bennet say this is normal and is why he recommends frequent oil changes. Oil pressure is now lower than I'd expected (below the 10 psi per 1000 rpm). The metal in the oil was ferrous material from ? and brass from the secondary ignition gear.

But here is my problem; the oil is a dark brown color and cloudy. Yesterday I flew for 1.5 hrs on fresh oil and changed it. It was dark brown. The local A&P said caused by carbon finding its way into the oil either because the cylinders were not scored correctly and I have problems with the rings or gas is leaking passed exhaust valve guides. He is recommending we tear the motor down and have a look. Any ideas for a less intrusive fix before I go to full open heart surgery?

Other than that, the motor runs great!

 

[soneraii]

My vote is for the tear down. Sorry. But it should not be that dark that quick and after 1.5 hrs. on an engine with 10 hrs TT, really should not be that cloudy either. I would expect after an hour and a half to have to look hard to see where the oil level is on the dipstick because it would still be almost clear in color and no cloudiness.

Sounds to me like you are grinding ferrous metals... who knows, maybe bearing surfaces, crank...

I would have to know everything was okay to continue to fly it.

Kevin

 

[slamdagin]

Will post what I discover when it's apart. Thanks

 

[Manu1]

Did you have your oil check? $25 from a company in fort wayne indiana (don't remember the name).
Emmanuel

 

[soneraii]

Manu's suggestion is a very good idea.

The process is called Spectographic Oil Analysis. It is done all over the country for the aviation industry and just about everybody else that operates heavy equipment etc..

You can do it by mail. Find a company and usually they will send you a small bottle that only holds maybe four or so tablespoons, you put a sample of your oil in it, send it back and they will analyze it and give you a report.

The report will show the types of metal showing up in the oil and how much of each type. If they are familiar with your type engine they will go as far as to suggest where the metal is coming from.

At this point probably worth your time, trouble and money.

Kevin

 

[Manu1]

This is the company i use.
http://www.blackstone-labs.com/

Emmanuel

 

[cliffrosa]

What has Steve from GPAS said? Does he know that your gonna tear it apart?

 

[slamdagin]

Thanks for the Blackstone Lab link, I sent away for a sample kit. I've taken two samples before as baselines but never knew where to send them.

I wont hear from Steve until today and he'll probably recommend less but he isn't flying in behind the engine. I stripped off all the accessories yesterday to make pulling the engine easy. Here are the "whats" I noted that will help lead to the "why":

1. poor man's compression test (hand propping) showed one cylinder with good pressure, two with medium, one low. Mechanic will do a compression test today (albeit on a cold engine) and report on leaks.

2. oil leaks from front seal and secondary ignition - due to overpressure in the case

3. Poor vent tube. I had a 90 degree to airflow tube originally and will change that to a larger end tube that ensures suction.

Then there is the question of where did my oil pressure go. If my problem turn out to be a ring seating issue and all that FE got pumped through the bearings, how much where did that abrasion do in 10 hours? We'll see what the master (Steve) says.

Greg

 

[oahupilot]

Take that engine oil analysis with a grain of salt, back when I fixed helicopters for a living we where required to do regular oil analysis on the turbines and transmissions. In all my multiple years of having it done it never detected a problem I could not see with my own eyes before sending the sample off to the lab.

As for black labs a friend of mine used their service on his subura wrx engine build which produced 400 hp. He did a baseline and then did samples at regular oil changes, all and all he did not learn anything from the oil samples.

 

[slamdagin]

Steve offered vented valve covers to help with the oil leaks in the front and distributor seals but admitted that this wont address the real problem of why after 1.5 hours the oil is dark brown. I also had a compression test done and was surprised by the results: 74/70/74/74. The engine was cold so a warm engine would have improved these numbers but I was expecting to find a leak, but we did not. So the next step is to open it up and look. I've got a mechanic in the area with a lot of experience with VW aircraft engines to assits/lead the effort.

 

[cliffrosa]

Did you get a chance to tear it open?

 

[slamdagin]

Yes, we tore the engine apart two weeks ago and I'm waiting for the mechanic to polish the crank so we can order bearings to begin the reassembly process. There was no big smoking gun as to why the oil gets so dirty looking with so little time on the oil but we did learn the following.

The bearings were pretty ugly looking as a result of all the metal chips being pumped through the engine and that is most likely why i saw a decrease in oil pressure as the engine broke in. Bearings need to be replaced. Crank looks good.

The piston rings were about 80% scored and the cylinders looked good. There were light scratches on the sides of the pistons but they are still good.

The secondary ignition gears still had metal shards on the gears ends from the manufacturing process that I needed to clean up with a Dremel tool because they will eventually break free into the oil. That problem exits on other gears as well like the brass gear that powers secondary ignition.

We are going to plug the oil galleys and add a remote oil filter. The first Empi kit I ordered was so far off square that the oil filter when tightened still left a gap with daylight between the gasket and mounting surface! GPASC replaced for free...but that was all. Bearings, new oil cooler will be on my dime.

If you are mechanically inclined, I'd recommend you build your engine up yourself following the instructions and with the help of an experienced VW mechanic.

Pix

 

[JuergenA]

Hi Greg,
check the oil pump housing inlet and outlet similar it is documented in the GPAS engine assembly on side 21
I had a problem some years ago with a wrong oil pump (not from GPAS!) where the oil input hole was too deep inside the case and so, the pump pumps oil AND air to the oil gallery. Air inside the oil is a very bad mixture!
with best regards
Juergen

 

[Gaston]

Hi Guys

I don't believe internal engine wear has an impact on oil colour and cloudiness ...
I've seen lot of metal deposit in different types of engine with normal oil color,I
had a cam / lifter combo worn out in about 60 or 70 hours with nothing to note relative to oil color.

I would think it has much more to do with very bad carburation and carbon washing into the oil...

a 10 hours breaking period is way too long for me and will only add chances of poor piston ring setting, and better chances to get carbon in the oil...

Hope this helps
this is only my personal opinion

Gaston

 

[slamdagin]

An update to my engine problems... The engine is back together with remote oil and flying well. Had to overcome oil leak issues (several). The aftermarket pump cover wasn't flat and pressure was still too low. After removing the thin gasket and wet sanding the aluminum cover flat, I was able to get an oil cover/pump gear clearance of about 0.0015. Oil pressure is still not as much as I'd like when the engine is hot. I may change to 20W50 at some point.

I changed the oil at 5 hours and it looked great. I also changed the crankcase vent system during the down time to improve airflow. I think the reason I had dirty oil before was because the crankcase vent was small and was providing a negative pressure and not venting the case.

Thanks for the help!
Pix