Thread: Quart of oil in 3 weeks

Hey all, first time poster here; long history speech but please, bear with me:

I bought my GT (1998 3.8L Series II N/A) 13 months ago, and two weeks later got rod-knock on a road trip. Had about 150k miles on it.

I had the engine rebuilt by a machine shop, and put in by a really good backyard mechanic my family has had nothing but great experiences with. We didn't have enough oil when he was putting it in (about half a quart short), so he recommended I top it off. I accidentally put half a quart or so too much in, and drove it for about 5-10 miles like that. I started leaking oil within the next few days, took it back to the machine shop and they said I saturated the rear engine seal by having too much oil and that was why it was leaking. I found if I parked facing downhill, it wouldn't leak. It's been a few months since I noticed any drips.

I am about 5.5k miles and 11 months on the rebuild, and now I'm burning oil like a MOFO. I changed my oil 3 weeks ago and I'm down over a quart. I checked the PCV Valve, which was clicking around fine, but it was covered with oil; I replaced it anyway just in case. I'm assuming I have oil in my intake plenum as well, but haven't taken it out to check.

My question to you guys is, what other possible factors could cause this much oil consumption? The engine doesn't seem to have any other vacuum lines associated with the PCV system; could it be blocked somewhere else and still sucking up oil through the valve? Or is it more likely something serious, like a bad intake manifold/head gasket seal or something?

Sorry for the TLDR; it's a long story.

P.S. The machine shop ****ed up the rebuild and didn't torque down a rocker arm bolt, causing the engine to misfire and the bolt to back off a half inch over a 2 block drive. I don't trust these guys.

valve seals?

Supposedly they were replaced as part of the rebuild. I'll check the invoice and make sure.

well is the motor burning the oil or leaking it?

Definitely burning it; I first noticed the smoke a month and a half ago. Took off from a left-turn light and there was a huge cloud of bluish-white smoke behind me.

The smoking is intermittent. It's also accompanied with the engine temperature increasing to a fully open thermostat, at which point the fan kicks in and keeps it at about 210. During this it smokes lightly during idle and dumps smoke during acceleration.

I just passed smog 4 weeks ago, and I'm fairly certain it wouldn't have passed if it was smoking at the time.

hmm.. valve seals normally show up as puff when starting it up.

Replace your pcv valve and see what that does for you. I've heard an improperly working pcv valve can cause oil loss

Originally Posted by OH4CompG

Replace your pcv valve and see what that does for you. I've heard an improperly working pcv valve can cause oil loss

I've already done that (since it was so cheap). I was exploring the region and realized that I forgot to swap the old lower o-ring for the PCV Valve. I didn't even check to see if the old PCV Valve had one.

This problem was why I changed the PCV Valve in the first place, so it was definitely occurring before I forgot the o-ring. Assuming it was bad and/or missing in the first place, we might have the problem! I'm going to go change the upper and lower rings as soon as I get off work, in addition to cleaning the MAP sensor since they're both in the same housing on this engine and it's probably covered in oil.

I did have an EGR Valve Vacuum Insufficient OBD-II code show up several times, even before the engine failed in the first place. Also my fuel economy is crap (10-15mpg city atm).

that might be the problem.

I ran it easy for the first 1k miles and changed the oil after I hit that mark.

So, I did some more looking around. Turns out that a mechanic who worked on the car before I bought it broke the MAP off, and super-glued it back together. That would explain the horrible gas mileage, horsepower, and EGR Insufficient Vacuum error code.

I also replaced the missing o-ring last night, and topped the oil back off. We'll see how she runs over the next week