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#1
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Oil runs low every month, but no leak?
Hi everyone,
Recently (past 3 months), I noticed my oil pressure gauge would drop way down. So, I would replace with 2 quarts (and some leak stop stuff) and pressure returns. Then about a month later it happened again and I would repeat fix. Today I just did it again. I have looked in engine bay for oil leak, and under car...nothing. Is this textbook valve seal issue? I know that everytime I do an oil and filter change, about mile 30 on the freeway I start to see smoke...then about a day later it just stops (no smoke/pressure fine/runs great).
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Current: 1971 Mercedes Benz 250 (Euro Spec) 1972 Mercedes Benz 250 (US Spec) Past: 1972 Mercedes Benz 280 |
#2
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Pressure and oil level are unrelated (unless you're so low on oil you're running low on pressure in which case you'd already have done major engine damage). Are you confirming low oil levels on the dipstick? Otherwise, it sounds like your oil pump is on the way out and/or its screen is clogged.
You can burn enough oil to go low but not see smoke with dirty or worn rings, they just aren't worn enough to show excessive smoke.
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Current: 2021 Charger Scat Pack Widebody "Sinabee" 2018 Durango R/T Previous: 1972 280SE 4.5 2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi" 1999 Chrysler 300M - RIP @ 221k |
#3
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Interesting...I saw the oil pressure go crazy a few days ago (at steady speed, it dropped down below 1, then back up to 3). Did this a couple times then stabilized.
Kind of seems like a clogged/malfunctioning pump?
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Current: 1971 Mercedes Benz 250 (Euro Spec) 1972 Mercedes Benz 250 (US Spec) Past: 1972 Mercedes Benz 280 |
#4
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Oil Pressure Gauge (Mercedes)
As "Optimistic" as the MB O.P. gauges are...
[I'll always believe they are Only a "RePresentation" of what Oil Pressure "Might Be"...] If "At Speed" (AKA anything over 1500 RPM) the OP drops,I'm turning the Key to Off ,even if I'm in the Midst of the Left hand lane of an Interstate !!!
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'84 300SD sold 124.128 |
#5
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Yep...its parked now till I figure this out.
You know I guess my question re-phrased is: what does an oil gauge really tell you? I mean when you have alternator issues, light flashes. When gas runs out, light flashes (and gauge gives you heads up). Break fluid low, light flashes. On other cars I have, when oil is low light flashes. So, why not just have a low oil light. What info does a constantly changing oil gauge tell you (my gear shifted from 1st to second gear?...redundant but ok). What value does this hold?
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Current: 1971 Mercedes Benz 250 (Euro Spec) 1972 Mercedes Benz 250 (US Spec) Past: 1972 Mercedes Benz 280 |
#6
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An immediate drop in oil pressure will cause severe engine damage. The oil light in most cars isn't an oil level light but an oil pressure light (newer cars have both, or will actually tell you on a fancy display either "Oil level low" or "Oil pressure low").
The dipstick is the way you tell the oil level. This should be done at every fill-up on any car we'd be discussing in these vintage forums, and more often (such as before every trip) if a leak or burning of oil is suspected. On the bright side, these engines hold a large volume of oil, so checking once per fill up even if you burn a fair amount should still suffice. There is only one point to having an oil pressure gauge. It's so you can monitor the health of the engine, just like temperature - except more vital. Most modern cars don't have an oil pressure gauge (and only use a light) because people don't understand why it fluctuates, or what it really means. Similar to the heart in the human body, your oil pump distributes vital lubricant to your engine. A heart attack - or, in the case of a car, an oil pump failure - can result in significant damage. If you're cruising and your engine is doing, say, 3000 RPMs, and all of a sudden that lifeblood stops pumping, your pistons are still moving up and down at, say, 9 meters per second (redline being closer to about 15 m/s). So the oil film that was on the piston/rings/cylinder will quickly be washed aside, leaving metal on metal contact. So if your engine loses lubrication for 5 seconds, that means your piston went up and down 250 times. Think about the damage an unlubricated piston can do during installation in an engine, and multiply that by 250. Then add the heat of combustion and friction from the rapid movement - you get the idea. The oil pressure gauge is there to tell you to shut the engine off the second you see a big fat "0" on it for any period of time. There are other possibilities that can cause a bad reading, such as a leak or blockage in the line that feeds the gauge, but if you're suspect of the gauge, a secondary one must be used to verify if you're going to continue driving!
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Current: 2021 Charger Scat Pack Widebody "Sinabee" 2018 Durango R/T Previous: 1972 280SE 4.5 2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi" 1999 Chrysler 300M - RIP @ 221k |
#7
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Crap...so engine is a no crank no start...think my engine just died
New starter, new alternator, new coils, new battery...oil pressure drop, 2 days later car won't crank.
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Current: 1971 Mercedes Benz 250 (Euro Spec) 1972 Mercedes Benz 250 (US Spec) Past: 1972 Mercedes Benz 280 |
#8
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Not to beat up on the owner of a Dead Horse...
Well,not Much.
Formerly,On "Determined to Kill a (Modern) Four Stroke Engine": "Recently (past 3 months), I noticed my oil pressure gauge would drop way down. So, I would replace with 2 quarts (and some leak stop stuff) and pressure returns." " (and some leak stop stuff)"... " (and some leak stop stuff)"... " (and some leak stop stuff)"... ________________________________________________________________ I'll risk a Prognostication,in this Case. If (Whenever) a Forensic tear-down of the engine is accomplished,It shall be found that a large portion of the Oil Passages are Clogged By... Wait For It... "Some Stop Leak Stuff" OF: " (and some leak stop stuff)" ______________________________________________________________________ For future reference: Never,Never,Never,EVER put Anything,Other than, the Properly specified Motor Oil (ONLY)in the Sump. ______________________________________________________________________________________ ______________________________________________________________________________________ In Re your reply # 7 above: "No Crank,No Start" Are you saying when you turn the Key to the "Start" Position there is no action ? [I.E. "No Crank"] AKA Absolutely No Noise At All From the Starter? No CLicks,No Buzzes,nothing? For example,If I were to Weld the Crankshaft into the Main Bearing supports and the Crankcase, and then engaged the Starter,there would Be Some sort of "Strain" noise from the Starter system. "No Crank" is almost always a Electrically related Difficulty. ___________________________________________________________________________________ I do believe you've got more than One difficulty.
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'84 300SD sold 124.128 Last edited by compress ignite; 02-06-2015 at 03:24 AM. |
#9
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Well, pretty bummed. Just closed on a house last Friday and renovations, closing costs, etc.. Funds are low (wife's gonna be pissed; I can see it now, "sweet heart, can we hold off on wood floors and paint so I can get an engine...it's the stuff of nightmares).
Holding out hope that it may be coils (gonna test this this weekend; spark test; Check it with Ohm meter). But ya, I turn key and sound like it stuck on something (thunk noise). I'm gonna try to turn engine by hand (pull plugs, etc). If it's not coils, and it is engine: do I have to take whole thing out, or is it just Pistons?
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Current: 1971 Mercedes Benz 250 (Euro Spec) 1972 Mercedes Benz 250 (US Spec) Past: 1972 Mercedes Benz 280 |
#10
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To get to the engine internals, you'll need to pull it out. The subframe will prevent the oil pan from coming out.
It's possible the engine seized because of an oil pump seizure. Trying to be positive for you. It's not the most likely thing, but it is possible. There are other possible causes as well. That all being said, it does not sound promising, and I'm sorry to hear this happened. The timing is never good to lose an engine. I can tell you it is not coils. Coils will prevent an engine from starting but would have no effect on cranking. If an engine will not crank, the starter and the battery and the items that connect them (Battery cables, starter solenoid, etc) are the only potential causes aside from a seized engine. It's easier to get to than the crank bolt: Try to turn the power steering pump shaft by the nut. You can use a wrench with a cheater bar on it. Try turning backwards if forwards will not go. If you can go backwards a bit, and then it stops, it would possibly indicate a seized cam, or valve/piston interference, as opposed to piston seizure.
__________________
Current: 2021 Charger Scat Pack Widebody "Sinabee" 2018 Durango R/T Previous: 1972 280SE 4.5 2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi" 1999 Chrysler 300M - RIP @ 221k |
#11
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Remove the spark plugs to make it easier to use the P.S. method.
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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.” ― Brian P. Cleary, You Oughta Know By Now |
#12
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Something to listen for...
If, when you turn the key to start, you hear a loud 'thunk' that is the starter trying to engage. The starter is doing its' job but the engine cannot turn. If you hear nothing then you might have a starter problem. You might hear some relays click but the starter hits with a rather solid sound. Do remove the plugs if possible and try to turn the engine over by hand. Your troubles might not be as bad as you think. |
#13
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Thanks for the words of encouragement, I hope it's simpler than I fear.
Does anyone remember size of bolt to manually turn engine? Should I take engine cover off and look for damage?
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Current: 1971 Mercedes Benz 250 (Euro Spec) 1972 Mercedes Benz 250 (US Spec) Past: 1972 Mercedes Benz 280 |
#14
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Easy,Peasey
You don't have to remove the "Valve Cover" (Engine Cover) to "Gently" test
for "Interference" (Lockup). Do Pull the Spark Plugs. The Diesels all use 27mm Hex Head Crank Bolts (Someone will chime in [Soon] with the size of the Petrol version) Turn the engine in It's Proper Rotation Direction ONLY! No COUNTER ROTATION Gently attempt to turn the Crank by hand...
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'84 300SD sold 124.128 |
#15
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The only time I ever had to turn a gasoline engine by hand it was on a M-100. That took a 50 mm socket.
What type of engine are we talking about here. It seems I missed that part. |
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