Oil Consumption

Leaking oil pressure sender? You are lucky if this the cause. Very inexpensive to replace. As well as the valve cover gasket. Could also be valves leaking oil in the combustin chamber. Do you see oil spots on the ground where you park for several hours? If not oil is probably burned in the combustion chambers , in which case your tail pipe should have black deposits.

Miatas *always* have black tailpipes, unless they're never driven at full throttle.

Brian, have someone else drive your car while you follow. If you see or smell oil smoke, it's bad news.

Well you can eliminate #s 1 and 2 and any type of leak right away. If it was leaking a quart every 500 miles you would have a gigantic mess and wouldn't be writing here to ask where the oil's going.

Pretty safe bet that it's burning. The only question is why it started. If all you had done was the timing belt replacement, I can't think of anything he could have done that would cause this.

John ('94 Miata)

jsgmcclary at cox dot net

The guy changed timing belt at 60200. Also replaced power steering & alternator belt; spark plugs; fuel filter; anti freeze; and transmission oil. Jiffy Lube changed the oil @60588, and that was when white smoke came billowing out of tailpipe. Mazda then did pressure check on cooling system and found no leaks in head gaskets. At that time they said on the notes that Oil drain plug was leaking oil. Then, @71K I went into Mazda (for what reason I have no idea) and they found leaking head gaskets. Also there was some type of leak around the drive belts and/or timing belt (I think it was the crank angle sensor O ring and / or the seals around the three belts replaced). Mazda replaced 2 head gaskets, crank angle sensor O ring, coolant hose @ engine block, steel separator tube, timing belt, AC / Power steering belt, Alternator belt, and seals around drive belts.

So is mine. :)

That is how I got to be a quite capable mechanic after a life of shoving that sort of thing off to my younger brother. I bought an MGB and was sick and tired of being stranded every time. So I bought a Haynes manual and a multimeter and started searching. Turned out that the shop had shorted the voltage stabilizer to earth. (The casing was earth, both terminals were +). It did not stop me from being stranded, but it did get less clockwork, and was nonelectrical from then on.

Leon

Thanks to all you guys for the help.

The head gasket should NOT need to be removed or changed when changing the timing belt (which runs from a pulley on the crank shaft at the bottom of the engine to pulleys on the two camshafts at the top of the engine). It is normally hidden behind a cover on the front of the engine. However, the valve cover does need to be removed and does have a gasket that may not have been replaced or installed correctly. Also, depending on how the timing belt was removed, the front main seal could have been damaged (sometimes replaced at the same time as the timing belt).

Even if you have someone else do the work, it is a good idea to learn and know about your car. At the very least, this gives you the ability to know that the mechanic is doing appropriate work. Even more important, knowing about your car can save you big $$ and time in an emergency. For example, a couple of months ago my Miata overheated for the first time. It was a hot friday afternoon so the chance of getting a mechanic was pretty slim. After pulling over and letting it cool, I was able to observe that the problem was that the cooling fans were not running even when the engine was hot. I was also able to confirm that coolant was not leaking from any where (no green liquid on the ground). Pulling out my Haynes manual, I found that the cooling fans are controlled by a sensor located at the front of the engine (on the intake fitting on top of the water pump). When I checked to see that the connection was good, I noticed that the sensor itself was broken (e.g., literally two pieces). So, the solution was easy, fill the overfill with cold water, drive to the nearest dealer (the car did not overheat as long as I kept air moving over the radiator), and buy a new sensor. Of course, I did not change the sensor until the next morning when everything was cool (when the engine is hot the coolant is under high pressure and can spray out and cause burns). Problem solved.

I'm not sure I agree. I have had leaks from the rear main seal that didn't leave much of a trace on the garage floor or anywhere else you'd notice unless you were under the car or looking with a light. I've also had leaks that only occurred when the oil was under high pressure (e.g., cold starting). However, absolutely correct that one should be able to find most leaks by looking if you know where to look. One approach that can help is to have the engine steam cleaned and then look for new appearance of oil (e.g., running down the side of the block from the valve cover gasket, running along the bottom of the tranmission from the rear main seal, along the oil pan from the oil pan gasket or the oil plug gasket).

Gus (91 BRG)

I had a similar problem on my 96. Turned out to be the valve cover gasket leaking near the back of the engine where the cam sensor is mounted. At least I think it is the cam sensor. When looking at the engine it is on the rear right and is round in shape. The valve cover is curved to accommodate it. The oil was running down the back of the block which makes it hard to see and it buns off from engine and tyranny heat. Bell housing was covered with oil as well.

Fix is to replace the valve cover gasket and take care in sealing this area well. Shop manual calls for extra sealant in that area.

One possibility. Could the engine have overheated while in the shop. If the mechanic drained the coolant and changed the hoses as you said, he may have had an air pocket in the water jacket, or didnt fill it completely. That could cause a leaky head gasket, and oil consumption by leakage into a cylinder, or into the water jacket. Just a thought.

Maybe it is the Valve cover gasket. That would probably be the simplest thing to try at this point. However, I do not see any oil on the Bell Housing. Is it typical for a Valve cover gasket to deteriorate over time? I saw in the Haynes manual that when my mechanic replaced the timing belt he had to remove the valve cover. Maybe he did not get the seal properly done when he put it back. I looked all around the Valve cover gasket and saw no noticable signs of oil leaks (just typical oil stains). With a quart leaking every 500-1000 miles, would there be noticeable oil all over the place? Or could it be being burned off?... You said from engine and tyranny heat; Well engine oil withstands very high temps inside the engine, how would it burn off outside the engine? What is tyranny heat? Brian

accommodate

I think we are in agreement since we both agree you should be able to see the evidence from an oil leak. However, some people may not know where to look.

Gus (91 BRG)

From the workshop manual, it appears that you can do it from below the car, though you need to lift the engine slightly with a hoist.

Unfortunately, my scanner is complaining about its RAM.

Leon

mac wrote

As Leon mentioned, the shop manual *says* you can get the pan off with the engine lifted slightly. Joey at PBC preferred to pull the engine when he replaced my oil pump.

-- Ken Lyons '97 Brilliant Black/'90 Classic Red Inside the Beltway [Remove the first two digits to reply]

Brian,

Is this loss of oil constant or was it a one time event? Have you driven an additional 500 miles (or multiple 500 mile segments) since you reported this and have added a quart of oil every time?

No smoke; no leak; no oil in water or water in oil. Doesn't add up; we are missing something.

Ken