Lebowski Posted June 24, 2018 Share Posted June 24, 2018 ...after I drove it around for an hour in 85 degree heat. I had it up to 80 at one point for about a mile then backed off to 60 so could that have had something to do with it? The car doesn't have an oil pressure gauge so can I rent something from Advance Auto Parts to see what my oil pressure is? It's only half a quart low and there are no leaks on the garage floor. Any suggestions would be appreciated. Thanks... Link to comment Share on other sites More sharing options...
TerryB Posted June 24, 2018 Share Posted June 24, 2018 Pressure sensor in the block acting up? 1 Link to comment Share on other sites More sharing options...
Lebowski Posted June 25, 2018 Author Share Posted June 25, 2018 21 minutes ago, TerryB said: Pressure sensor in the block acting up? I'm not much of a mechanic so I don't know. Where is it and how can I tell if it's acting up? Thanks... Link to comment Share on other sites More sharing options...
Bloo Posted June 25, 2018 Share Posted June 25, 2018 The switch could be anywhere an oil galley appears on the outside of the engine. Is this a small block Chevy? If so, look back right next to the distributor. if it isn't there, look up on top of the oil filter. When you find it, turn the key on (not running), and see that the light is on. Pull the wire off of the sensor. light should go out. If the light stays on, look at the wiring. Put the wire back on and start the car. If the light wont go out, you either have a bad switch or no oil pressure. Don't run it anymore until you figure it out. You could try another switch, or better yet, get a cheap mechanical oil pressure gauge, of the underdash type, to use as a diagnostic tool. I keep one in my toolbox. Was the light on just at idle? If so, it might just need one step thicker oil for the hot weather. I wouldn't assume that though, find out what the pressure really is and then make a decision. The oil pressure switch takes a special socket. Sometimes a deep 6-point socket works fine, sometimes not. The socket is about 9 bucks at oreilly if you need it. Put sealer on the threads of the new switch, something like Indian Head, Permatex #2, or teflon thread sealer paste (pipe dope), whichever you have laying around. I wouldn't use tape and risk it snaking its way into the oil galley. The oil pressure switch looks something like this: Link to comment Share on other sites More sharing options...
Lebowski Posted June 25, 2018 Author Share Posted June 25, 2018 6 minutes ago, Bloo said: The switch could be anywhere an oil galley appears on the outside of the engine. Is this a small block Chevy? If so, look back right next to the distributor. if it isn't there, look up on top of the oil filter. When you find it, turn the key on (not running), and see that the light is on. Pull the wire off of the sensor. light should go out. If the light stays on, look at the wiring. Put the wire back on and start the car. If the light wont go out, you either have a bad switch or no oil pressure. Don't run it anymore until you figure it out. You could try another switch, or better yet, get a cheap mechanical oil pressure gauge, of the underdash type, to use as a diagnostic tool. I keep one in my toolbox. Was the light on just at idle? If so, it might just need one step thicker oil for the hot weather. I wouldn't assume that though, find out what the pressure really is and then make a decision. The oil pressure switch takes a special socket. Sometimes a deep 6-point socket works fine, sometimes not. The socket is about 9 bucks at oreilly if you need it. Put sealer on the threads of the new switch, something like Indian Head, Permatex #2, or teflon thread sealer paste (pipe dope), whichever you have laying around. I wouldn't use tape and risk it snaking its way into the oil galley. The oil pressure switch looks something like this: Thanks for all the info. It's a big block 396 which was professionally rebuilt about 1000 miles ago. The light doesn't go out when I rev it up. Is the sending unit on the passenger side just above the oil dipstick? I turned on the key and unplugged the wire from it and the idiot light was still on. Also, (maybe I should have mentioned this earlier) when I tried to start it after letting it sit in the garage for 3 hours after my drive, it was hard to start and when it finally did the idiot light flickered for a few seconds but after I revved it up a few times it stayed on without flickering so I don't think it's a wiring problem. Can I buy an oil pressure gauge and screw it into the sending unit hole without attaching any wires to anything or is it more complicated than that? Link to comment Share on other sites More sharing options...
Bloo Posted June 25, 2018 Share Posted June 25, 2018 1 minute ago, Lebowski said: Can I buy an oil pressure gauge and screw it into the sending unit hole without attaching any wires to anything Yes, but it sounds like you don't need to. 10 minutes ago, Lebowski said: Is the sending unit on the passenger side just above the oil dipstick? Probably. I think there are a bunch of plugs along the oil galley right above the oil pan, any of which could be used for the oil switch. This would be the same side of the engine as the oil filter. That's the passenger side isn't it? The plug up by the distributor (like a smallblock) might be there too. If you found something that looks like what I posted, you found it. The style of wire terminal could be different, and it might not have a long neck like the pic, but otherwise should look about the same. A water temp sensor, on the other hand, would probably have way bigger threads. 17 minutes ago, Lebowski said: I turned on the key and unplugged the wire from it and the idiot light was still on. If it was really the oil switch you found, this is a wiring problem. The sensor grounds the wire to turn the light on. Follow the wire and look for the spot where the insulation got rubbed through. Link to comment Share on other sites More sharing options...
Matt Harwood Posted June 25, 2018 Share Posted June 25, 2018 I would bet it's the sending unit. I think they are designed to activate below 8 or 10 PSI. If your car really had 8 or 10 pounds of oil pressure, you'd hear it ticking in the lifters and rockers. So I think the engine is OK. Change the sending unit as Bloo describes and see what happens. I've had this happen on several cars before and yes, a hot day can kill a sending unit that's marginal. But I don't think your engine is hurt or you're running it without oil pressure. You can also buy a mechanical oil pressure gauge that matches your new temperature gauge and thread that into the sending unit's hole and have a more accurate reading. They make flexible tubing or braided stainless lines that make it easy to hook up an oil pressure gauge. I've used copper tubing before as well, but in a vibration-prone car like a Chevelle, you might get some work hardening and the line could crack. Use the braided stainless line from Summit that already has the ends installed. No worries, this is a minor thing. Your engine isn't hurt. Let us know what you find! Link to comment Share on other sites More sharing options...
tom_in_nh Posted June 25, 2018 Share Posted June 25, 2018 If it was my car, I would err on the side of caution. Do not continue to operate the engine until you get an exact pressure reading. What if you do in fact have a problem with your engine's circulatory system? Can't you hear the hundred dollar bills flying away? Most especially on a big block... Do let us know how this turns out. Best of luck. Tom 1 Link to comment Share on other sites More sharing options...
Lebowski Posted June 25, 2018 Author Share Posted June 25, 2018 I forgot to mention that the sending unit that I unplugged the wire from had two prongs on it and the one pictured above appears to only have one prong. Should that make any difference? There was no ticking from the lifters. If 10 psi is low how many psi is normal? My next door neighbor is coming over in the morning to try to help me figure this out. Thanks again... Link to comment Share on other sites More sharing options...
padgett Posted June 25, 2018 Share Posted June 25, 2018 (edited) I remember Herb Adams telling me that 400s did not need any pressure at idle, just some flow is enough. That said an idiot light should be out by 1200 rpm hot (unless you have 5-15 Mobil 1). GM shop manuals say when in doubt, use a mechanical gauge. One possibility I have seen is a stuck oil pressure relief valve - simple fix but expensive if not done. Should have 40-60 psi at speed. The old time saying was 10psi per 1,000 rpm. Edited June 25, 2018 by padgett (see edit history) Link to comment Share on other sites More sharing options...
Willie Wurke Posted June 25, 2018 Share Posted June 25, 2018 The first thing to do is READ THE OWNERS MANUAL!!! I have a 1993 Chev with the 350 fuel injected with Auto trans. My manual states that on a warm day , after a sudden stop,the light might blink on. THIS IS NORMAL ( and mine does it ) Link to comment Share on other sites More sharing options...
Bloo Posted June 25, 2018 Share Posted June 25, 2018 (edited) What year is the car? There are 2 wire oil switches, but not so common. Two wires sounds like maybe hot/cold lights? Do you have that setup? It looks like the oil filter is on the drivers side, not the passenger side. I think thats it at the back, and you can see the row of plugs in the oil galley coming forward. It is probably along there, or up by the distributor like a smallblock... I think. Edited June 25, 2018 by Bloo (see edit history) Link to comment Share on other sites More sharing options...
DAVES89 Posted June 25, 2018 Share Posted June 25, 2018 With 1000 miles on the rebuild I would take it back to the builder with your concerns. Then if you want a gauge ask him to install it for you. This will give both you and the builder peace of mind. 2 Link to comment Share on other sites More sharing options...
Lebowski Posted June 25, 2018 Author Share Posted June 25, 2018 8 minutes ago, DAVES89 said: With 1000 miles on the rebuild I would take it back to the builder with your concerns. Then if you want a gauge ask him to install it for you. This will give both you and the builder peace of mind. I bought the car in November 300 miles away in northern Indiana after the frame-off resto had just been completed so it's not possible for me to do that.... Link to comment Share on other sites More sharing options...
Lebowski Posted June 25, 2018 Author Share Posted June 25, 2018 My neighbor came over and I told him the oil was about 3/4 of a quart low so I added a quart and the idiot light went out. It would stay off when I revved it up and flicker momentarily when the engine speed decreased to idle and then it would go out and stay out while it was idling. He thinks the wrong dipstick may be in there and it may have been 2 quarts low. Should I add another quart to see if the light stops flickering after I rev it up? What is the correct length of the dipstick for a 396? Is there a part number on it somewhere? Also, he found the sending unit which is on the driver's side above the oil filter like someone here said it was. When the wire is removed the idiot light went out so the wire is attached properly. I would still like to find out what the oil pressure is. When I remove the sending unit will oil come out of the hole? Link to comment Share on other sites More sharing options...
DAVES89 Posted June 25, 2018 Share Posted June 25, 2018 I believe the oil light should come on when you are a quart low. The oil sending unit is above the oil pan so you might get a bit of seepage but no it won't drain out. Now is the time to take the car into your local garage and have an oil pressure gauge installed if that is what you want. Then you will have both a light and a gauge. If you are not sure on the dip stick length either order one on line or get one from a dealer or local parts house. Link to comment Share on other sites More sharing options...
TerryB Posted June 25, 2018 Share Posted June 25, 2018 A direct reading gauge is the way to go. The dipstick question is unusual but not out of the realm of possibility. You could do an oil change to be sure of the amount of oil in the engine. Don’t overfill, it’s not good for the engine. With a known amount of oil in the engine you can tell if the dipstick is correct. Oil change is relatively cheap and quick to do. Don’t forget to do the filter too just in case something weird is going on with it. 1 Link to comment Share on other sites More sharing options...
Zimm63 Posted June 25, 2018 Share Posted June 25, 2018 (edited) PUT A GAUGE ON IT!! I killed an LT1 350 about 40 years ago when I didn't believe the light. New engine, not properly primed. Dumb and expensive mistake. Bearings were shot, crank scored, etc. Edited June 25, 2018 by Zimm63 (see edit history) 2 Link to comment Share on other sites More sharing options...
oily rag Posted June 25, 2018 Share Posted June 25, 2018 I ran into a problem with a late 40s no oil filter Chevy 6 cylinder were dipstick tube was to short. The proper amount of oil would read as an over fill. Link to comment Share on other sites More sharing options...
capngrog Posted June 25, 2018 Share Posted June 25, 2018 (edited) 1 hour ago, DAVES89 said: I believe the oil light should come on when you are a quart low. The oil sending unit is above the oil pan so you might get a bit of seepage but no it won't drain out. Now is the time to take the car into your local garage and have an oil pressure gauge installed if that is what you want. Then you will have both a light and a gauge. If you are not sure on the dip stick length either order one on line or get one from a dealer or local parts house. All of the automotive oil pressure detection systems I've dealt with detected oil pressure only and not quantity. It would be great to have a system to detect both oil pressure and quantity, but I have no experience with those systems in automobiles. You are right about the oil sending unit. In the course of converting my SS396 Chevelle to 4 speed, I had to remove the oil pressure sensing line and fittings where they screwed into the block (these were replaced in that original position after the clutch linkage "Z bar" was installed). Only a little oil seepage occurred. I have both the oil pressure "idiot light" and an analog oil pressure gauge installed in my Chevelle. The "idiot light" can catch the driver's attention immediately upon loss of oil pressure, but the analog gauge can detect actual pressure variations. I measured the dipstick on my 396, and it is 21 inches long from the tip to the bottom of the "cap" that seats at the top of the dipstick tube. The oil "ADD" mark is 1-1/8 inches above the tip of the dipstick, and the oil "FULL" mark is 1 inch above that (2-1/8 inches above the tip of the dipstick). The GM 1968 "Chevrolet, Chevelle, Camaro, Chevy II and Corvette Chassis Service Manual", page 0-9 lists the oil capacity for 396 and 427 C.I. passenger car engines to be 4 quarts, plus one quart for the oil filter (5 qt. total). Only the 427 Corvette engine is listed as 5 quarts plus 1 quart for the filter (6 qt. total). I hope this helps Cheers Grog Edited June 25, 2018 by capngrog correct a typo (see edit history) Link to comment Share on other sites More sharing options...
JACK M Posted June 25, 2018 Share Posted June 25, 2018 55 minutes ago, capngrog said: measured the dipstick on my 396, and it is 21 inches long from the tip to the bottom of the "cap" that seats at the top of the dipstick tube. The oil "ADD" mark is 1-1/8 inches above the tip of the dipstick, and the oil "FULL" mark is 1 inch above that (2-1/8 inches above the tip of the dipstick). The length of the tube comes into play here as well as the length of the stick. A simple oil change will get you an accurate amount of oil in the engine. I suspect that there are many variations on the lengths of aftermarket sticks and tubes. 2 Link to comment Share on other sites More sharing options...
JACK M Posted June 25, 2018 Share Posted June 25, 2018 Here is another thought. These screw in electrical senders, I don't think it is recommended to use sealer on them as they need to make ground to turn the light on. I have never had this happen but I think I may have read the directions once. Link to comment Share on other sites More sharing options...
ols car dog Posted June 25, 2018 Share Posted June 25, 2018 (edited) Did you check with the engine builder? They might have used a light weight "break in oil" change the oil and filter Use a magnet when you drain the oil to see if you have shavings . cut the oil filter open and inspect it also.. Put a GAUGE in the system or you will never know for sure!!? Ken Edited June 27, 2018 by ols car dog (see edit history) Link to comment Share on other sites More sharing options...
Lebowski Posted June 25, 2018 Author Share Posted June 25, 2018 3 hours ago, capngrog said: I measured the dipstick on my 396, and it is 21 inches long from the tip to the bottom of the "cap" that seats at the top of the dipstick tube. The oil "ADD" mark is 1-1/8 inches above the tip of the dipstick, and the oil "FULL" mark is 1 inch above that (2-1/8 inches above the tip of the dipstick). My dipstick is similar to yours except the full line is 3/4" above the add line and yours is an inch above it. I have the 1970 version of the service manual that you have. I'll change the oil and filter and see what happens. Thanks.... Link to comment Share on other sites More sharing options...
Spinneyhill Posted June 25, 2018 Share Posted June 25, 2018 As well as looking for shavings, look at the oil you drain. If it has a silver sheen, it has metal in it. Get it tested and the results will tell you what the metal is and from that you should be able to tell roughly where it came from. Then you decide what to do about it, if anything. Link to comment Share on other sites More sharing options...
capngrog Posted June 25, 2018 Share Posted June 25, 2018 1 hour ago, Lebowski said: My dipstick is similar to yours except the full line is 3/4" above the add line and yours is an inch above it. I have the 1970 version of the service manual that you have. I'll change the oil and filter and see what happens. Thanks.... By changing your oil and adding the specified amount of new oil, you'll be able to calibrate your dipstick and mark it yourself. I'm assuming that the oil quantities for the 1970 396 are the same for the 1968. You mentioned in your Post #3 above that you're "not much of a mechanic" so I hope you'll not be offended if I add this bit of "oil-changing" advice. Many folks (me included) recommend pouring a 1/2 quart of new oil into the new filter before screwing it back onto the engine block. In reality, this is probably not really necessary, but it does help restore oil pressure more quickly (maybe one second +/-). In addition, after adding the recommended amount of new oil, start and run the engine long enough to circulate the new oil throughout the engine (1 minute or so) then shut the engine down. Wait a couple of minutes for all of the circulated oil to drain back into the oil pan, and then check the oil level. That should be your true oil level. Cheers, Grog 1 Link to comment Share on other sites More sharing options...
Lebowski Posted June 26, 2018 Author Share Posted June 26, 2018 I changed the oil and filter this morning and didn't see any tiny bits of metal or anything else in the oil and the oil idiot light didn't come on. The oil level is about 1/8" above full on the dipstick. I'm not going to take it on any long drives in this heat (95 this weekend) so hopefully the idiot light will stay off. Thanks again for the comments and advice.... Link to comment Share on other sites More sharing options...
JACK M Posted June 26, 2018 Share Posted June 26, 2018 Take a file and make a mark on your dip stick at the true full mark. It will help you to remember. Or maybe figure out a way to cut an eighth off of the tube. Link to comment Share on other sites More sharing options...
padgett Posted June 26, 2018 Share Posted June 26, 2018 ""detected oil pressure only and not quantity" First car I had with an oil level detection was my '78 Sunbird V8. Today at least three of my cars (including both Reattas) have at least an oil level switch. One measures the level in inches. Being infested with Jags in my yout ("40 psi at 3,000 rpm...") have always been overly sensitive to oiling. Link to comment Share on other sites More sharing options...
Willie Wurke Posted June 27, 2018 Share Posted June 27, 2018 (edited) On 6/25/2018 at 10:58 AM, capngrog said: All of the automotive oil pressure detection systems I've dealt with detected oil pressure only and not quantity. It would be great to have a system to detect both oil pressure and quantity, but I have no experience with those systems in automobiles. You are right about the oil sending unit. In the course of converting my SS396 Chevelle to 4 speed, I had to remove the oil pressure sensing line and fittings where they screwed into the block (these were replaced in that original position after the clutch linkage "Z bar" was installed). Only a little oil seepage occurred. I have both the oil pressure "idiot light" and an analog oil pressure gauge installed in my Chevelle. The "idiot light" can catch the driver's attention immediately upon loss of oil pressure, but the analog gauge can detect actual pressure variations. I measured the dipstick on my 396, and it is 21 inches long from the tip to the bottom of the "cap" that seats at the top of the dipstick tube. The oil "ADD" mark is 1-1/8 inches above the tip of the dipstick, and the oil "FULL" mark is 1 inch above that (2-1/8 inches above the tip of the dipstick). The GM 1968 "Chevrolet, Chevelle, Camaro, Chevy II and Corvette Chassis Service Manual", page 0-9 lists the oil capacity for 396 and 427 C.I. passenger car engines to be 4 quarts, plus one quart for the oil filter (5 qt. total). Only the 427 Corvette engine is listed as 5 quarts plus 1 quart for the filter (6 qt. total). I hope this helps Cheers Grog Your idea if an oil level gauge in dash is old hat!! My 1953 Rolls-Royce Silver Dawn has a pressure gauge plus a push button below the gas gauge that when pressed will show engine oil level. I can check my oil while driving. If it shows "above minimum" all is well. Now you have reason to get a RR!! I don't think there is anything that has never been tried on an automobile!!! Edited June 27, 2018 by Willie Wurke to correct spelling errors (see edit history) Link to comment Share on other sites More sharing options...
fraso Posted June 28, 2018 Share Posted June 28, 2018 I have had oil pressure switches go bad on me. I have both the switch and pressure sender (for an aftermarket gauge) teed into the oil switch's port so I know how much pressure I really have. This keeps the oil pressure warning lamp functional so I know immediately if I loose pressure. The warning lamp should not light if you disconnect the switch. That indicates a short in the circuit. If your engine doesn't have worn bearings, a 30-grade oil should be adequate for your needs. Going to an oil with excessive viscosity means that more oil is relieved back to the sump and less reaches the bearings. See Engine Wear. 1 Link to comment Share on other sites More sharing options...
cheezestaak2000 Posted June 28, 2018 Share Posted June 28, 2018 might be a bit of a stretch, but, had a v10 doge and took it in for a recall for intake manifold gaskets. the dealer must have been in a hurry, and let a lot of the old gasket material stay wherever it fell. a couple days later, it all ended up in the oil pump pick up screen. this wiped out all the bearings in the engine. dealer's reply was sorry about you luck, and would do nothing to repair it. long story short, only used engine i could find for it was from a viper, so my truck got a little bit quicker after that debacle. 1 Link to comment Share on other sites More sharing options...
JustDave Posted June 28, 2018 Share Posted June 28, 2018 be real careful,the oil pump pickup falls off of chevy oil pumps,if the light goes out then that's not the problem,did you run it low on oil,if so you may have an air bubble in the line,if not then start checking the sender for the oil pressure (oil prassurs switch+ I believe on a big block chevy its either just above the oil filter or beside the distributor,either way good luck, dave 1 Link to comment Share on other sites More sharing options...
Lebowski Posted June 28, 2018 Author Share Posted June 28, 2018 I drove it around for half an hour today in 90 degree heat. After a few minutes the oil idiot light came on so I headed home. When I got here it was running fine with the fresh oil (Quaker State 10w40) that I put in on Tuesday so I'm pretty sure the problem is with the sending unit so I ordered a new one which will be here next week. Thanks for the input.... Link to comment Share on other sites More sharing options...
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