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Car Forum / Nissan / Nissan Cars / March 2006How to Replace/Repair/Block Oil Filter Bypass Valve on Engine???
Hi, Just changed the oil on my girlfriend's 96 Nissan Sentra 1.6 Liter. I changed to 20W-50, from 10W-30, in hopes of increasing the oil pressure a bit. The oil light has been coming on at idle, when hot. I have posted here before about it. As I was lying on my back under the car, with the oil filter off, I happenned to notice what looked like a steel spring inside a hole, just lying there, looking useless. This hole was one of three holes all of which get covered up when you screw the oil filter back on. I believe it is the hole for the oil filter bypass valve. I was able to pull the spring out of the hole, and push it back in ! I was also able to thrust a small screwdriver shaft down the center of the spring about 5 inches until the shaft struck the curve(?) of the tunnel. There was no cover over this hole, no lid, no valve, no nothing, just an open hole with a spring floating around in it. The edges of the hole are slightly raised, and rough, as though something had been there but was sheared off. Interestingly, the oil pressure light started coming on right after an oil change I did about a month ago. Maybe I broke it off somehow. I don't remember anything out of the ordinary except that the old filter was really hard to get off, and I had to get a new wrench to get it off. I checked the bottiom of the used oil jug, but didn't find any thing looking like a lid to the hole. I had a mechanic test the actual mehanical oil pressure, and it was at zero when hot and idling, and only went up to about 15 psi when he reved the engine to about 1500 or 2000 rpm. When I removed the old filter today, it was completely full, so oil is obviously getting into it (and through it, I hope) even with the bypass being open, and the pressure low. The oil filter goes on empty, and is full at oil change time. But maybe it is full just because oil drains down INTO it from above, when the engine is shut off ! Where has the broken off lid gone? Into the engine ? Maybe I threw it out during an oil change? How do I repair this? How can I check to see if it has been sucked up into the engine? If not repairable, how can I block off the bypass hole? I hope that this wide open bypass is the cause of my low oil pressure, and that fixing it, or just blocking it off will bring the pressure back up. Thanks > Where has the broken off lid gone? Into the engine ? Maybe I threw it > out during an oil change? > > How do I repair this? > > How can I check to see if it has been sucked up into the engine? Take the engine apart. > If not repairable, how can I block off the bypass hole? DON'T do that! > I hope that this wide open bypass is the cause of my low oil pressure, > and that fixing it, or just blocking it off will bring the pressure > back up. This sounds like the filter bypass, not the oil pressure relief valve. Sounds like maybe the former has gotten stuck in the pump pressure relief valve inside the oil pump and has it stuck wide open which would cause the problem you have. This valve is in the oil pump itself on most engines. I'd take/tow it to someone who knows what they are doing or else tell her to start saving money for a new engine.. If you keep driving it you're going to RUIN the engine if you haven't already.  SignatureSteve http://www.atlantaracing.com The oil pressure should be around 11 psi at idle, and at around 60-70 psi at 3000 rpm. By now you should know that the news is not good. Working the engine with low oil pressure means disaster!! The oil pump has a pressure regulator valve that protects against excesive pressure in the system. It consists of a spring that pushes a piston against a hole in the pump housing. If this is your problem, rest assured you did not cause it. I do not think this is your problem. The spring that you found in the oil filter area seems to be the pressure relief valve. This valve is intended to protect against filter damage due to excesive pressure in the filter. This seems to be the cause of your problem. Not sure for your engine, but in other nissan engines, the spring pushes a ball bearing against a valve seat through which, you can see and push the ball bearing against the spring. In those other engines, you can pry the seat out of its place and replace the spring,the ball bearing and the seat. Again, no way for you to have caused this problem. From experience with some older nissan engines, the ball goes through the worn out valve seat. Some oil filters have a by-pass valve, that works under the principle that dirty oil is better than no oil, and this valve is functional when the oil filter is clogged. This valve gets replaced every time you replace the oil filter. Problems with this valve would not affect the pressure too much. Parts from this valve should have no way of getting into the engine. I hope this info helps. Good luck, and please let us know what happens > Hi, > Just changed the oil on my girlfriend's 96 Nissan Sentra 1.6 Liter. [quoted text clipped - 47 lines] > > Thanks > The spring that you found in the oil filter area seems to be the > pressure relief valve. This valve is intended to protect against filter > damage due to excesive pressure in the filter. This seems to be the > cause of your problem. There are 2 valves, one is the filter bypass which is in the filter seat area and the other is the pressure relief valve which is near the pump inside the pan. A defective oil filter bypass valve will NOT cause low oil pressure. SignatureSteve http://www.atlantaracing.com > > The spring that you found in the oil filter area seems to be the > > pressure relief valve. This valve is intended to protect against filter [quoted text clipped - 9 lines] > > Steve AS and STeve T, Update : I bought the replacement valve from Nissan. $5.00. Went to install it, and the old one won't come out. Got a quote from Nissan dealer of $75 to replace it !! They say they have to drill the old one out, then press-fit the new one in. They say these valves almost never "break" like mine did. But one of the mechs there said he replaced one on a Pathfinder ... once. When I asked if having the valve wide open would affect the oil pressure , the service guy said "I have no idea ! " and he said the mechs there would not know either, since this is such a rare situation ! Just for a test, I placed a wide, flatheaded screw into the bypass hole, with the head covering the hole so it couldn't get sucked in, replaced filter, and went for a ride. The oil light still came on, in fact it came on sooner than without the screw. The screw shaft was blocking about half of the area of the bypass opening, so I at least slowed down the rate of flow thru the bypass, and hopefully sent some of the oil thru the filter. I removed the screw later, since the oil pressure light was still coming on, even sooner. I'm going to check out adding some STP type additive next. Also checking out the newspaper ads for used cars, since the gf is not doing it. This is pretty frustrating. The Nissan dealers seem pretty clueless, unless they're just playing dumb. Maybe just trading it in, or selling it as a "needs work" car is the thing to do. It has 177,000 miles, but I was hoping for more. Sorry to hear about the difficulty in replacing the valve. From a Nissan service manual, "pry the old valve using a suitable tool" The catalog does not mention a suitable tool, in the tool page for that catalog section. Is the damaged seat hole centered? If yes you can drill with a bit size just smaller than the outer diameter, the seat will loosen up once there is only a thin wall left. Is the hole vertical, sideways? You can always use a drill angle attachment (~25 from Sears or ~20 (smaller) from ebay) if space is limited. What about trying with a rod with a diameter that just fits the hole in the seat precisely? The really serious problem is bringing the oil pressure up: Damaged oil pump, regulator valve, or engine worn out. Good luck >>>The spring that you found in the oil filter area seems to be the >>>pressure relief valve. This valve is intended to protect against filter [quoted text clipped - 41 lines] > Maybe just trading it in, or selling it as a "needs work" car is the > thing to do. It has 177,000 miles, but I was hoping for more. << The really serious problem is bringing the oil pressure up: Damaged oil pump, regulator valve, or engine worn out. >> AS, Thanks for all the information and suggestions. Do you think that the filter bypass valve, in the block, in the filter area, being wide open is lowering the oil pressure? The purpose of the relief valve is to allow oil to bypass the filter if some idiot hasn't changed the filter in a REALLY long time and the filter is all clogged up. In the short term, this allows the engine to live because the bearings, etc., still get oil. In the long run, engine wear is greatly increased because there's effectively no oil filter and the oil gets really dirty and never gets cleaned. If the relief valve is failed open (or missing), if anything, there will be slightly higher oil pressure at the bearings, etc., because there's no slight pressure drop at the good oil filter. But for all practical purposes, there's no change, at least in the short run. In the longer run, the oil isn't going through the filter, so it gets dirty quickly, things wear, and the oil pressure goes down. And worst case, if the relief valve self destructed and scattered itself through the engine, the oil was abraseive about 10 seconds after the valve died. Now, if the relief valve fails closed, and the filter gets clogged, oil pressure at the bearings, etc., will go down because there's no flow. But that's not your situation because the relief valve is gone. > << The really serious problem is bringing the oil pressure up: > Damaged oil [quoted text clipped - 5 lines] > the filter bypass valve, in the block, in the filter area, being wide > open is lowering the oil pressure? >>>If the relief valve is failed open (or missing), if anything, there will be slightly higher oil pressure at the bearings, etc., because there's no slight pressure drop at the good oil filter. But for all practical purposes, there's no change, at least in the short run. In the longer run, the oil isn't going through the filter, so it gets dirty quickly, things wear, and the oil pressure goes down.<<<<< This seems like a likely scenario to me. But I would hope at least some of the oil made it through the filter during a typical drive. Then it would be operating, indeed, as a "bypass filter", like they have for diesel truck engines. But, I would guess this Nissan car is supposed to have 100 percent filtration during a most of a normal 20 minute drive. It's academic now, of course, since the engine is apparently quite worn due to age and/or lack of oil filtration. If I were to spend the $75 to put in the new valve, I would then have clean, filtered oil, but flowing at an even lower (slightly) oil pressure....... |
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