Oil Pressure Light + Hot Weather = Neurosis?
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Thread: Oil Pressure Light + Hot Weather = Neurosis?

  1. #1
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    Default Oil Pressure Light + Hot Weather = Neurosis?

    I'm observing a potential oil pressure scenario with my 1969 DS21 which has me concerned enough to reach out to the group for some thoughts.

    There might be coincidental symptoms here so I'm just trying to weed through the "noise" to get a sense of how i should approach ensuring the health of my motor. Not having an actual gauge to see what the pressure is helps to increase the mystery...only a warning light to help guide the way!

    Main Concern:
    I've noticed that my oil pressure indicator has begun to illuminate when my engine is at full operating temperature and revving at lower RPMs. The warning light persists until i exceed 2000+ RPMs while the engine is running hot...so i only see the OIL light illuminated while running around town in stop and go traffic (when the engine is running on the hot-side during the summer months here in LA)

    Caveats/NOTES:
    • I'm using 20W-50 syntec (classic formulation with Zinc) I changed the oil about 800 miles ago so it's relatively fresh. It's topped off at the "full" level. i had a paranoid thought revolving around the "arrows" somehow becoming mis-aligned on the oil filter after i installed it? Exceedingly unlikely i suppose but the mind wanders in these scenarios...
    • The engine tends to run hot according to the temp gauge but the engine has never overheated (and so i've always questioned my TEMP gauge accuracy) The hotter the engine the more RPMs required to get the warning light to turn off due to viscosity decreasing with temp.
    • I've noticed a similar scenario in my other classics (my old 1968 Porsche has a pressure gauge which always shows a drop to near 0 PSI in pressure while at idle with a hot engine)
    • The DS engine was rebuilt 3 years ago...probably has about 10k miles on it. I did not notice this light last summer during the hot operating period but that could be a result of the gauge being disconnected. I've recently gone through dash fixing some of the wiring issues i inherited from the previous owner....so for all i know this was happening last summer as well.
    • the engine does not sound or run as if it's oil starved when it's idling and while the OIL light is on...not hearing valves tapping or anything else that would indicate it's not happy....other than it runs hotter according to the aforementioned temp gauge.


    GOAL:
    Either learn to ignore the OIL light because it's one of those things everyone deals with (although i doubt that as i'm not able to find any other threads on this subject) or come up with a reasonable process of elimination to determine what is wrong. If the OIL PRESSURE is dangerously low and could damage the motor i certainly don't want to be putting it at risk.

    I've not driven the car on a "cool" day in a couple months so i'm not sure if this scenario goes away when the engine operates in the middle of the temp range?

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    Any thoughts i'm all ears/eyes!

    Thanks
    Pynhead
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    Hi Pynhead,
    The senario sound ok with the oil getting thinner when hot and the pressure low when idleing. However up to 2000RPM to put out the light is not good. But the sensor may be faulty ?
    The sensible thing to do, for me, is simple, put some real data into the equation and fit a gauge. Pull the sensor switch and put a T fitting under it and a line into a gauge so you can see what is happening. Mu-uch cheaper than a rebuild !!
    Jaahn
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    Try a 20W60 oil? Are there negatives to this idea for hot weather running?

    Cheers

    Alec

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    If the engine was indeed rebuilt properly then there should be not problem. As suggested put a gauge on it and find out what the actual pressure is when hot at engine idle. If the gauge reads low, then get a hold of the shop that did the work. A correctly rebuilt D engine at 10,000 miles is basically just getting well seated. If the gauge shows a low pressure problem the most likely cause is excessive gap(s) between the crank journals and their respective bearings.

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    I'm not sure i've seen 20W-60 on my local auto-parts store?!

    Makes complete sense to check the actual pressure and I'll check back with an update. Thanks for the quick response Armidillo, Citroenfan and Jaahn!
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    Quote Originally Posted by Armidillo View Post
    Try a 20W60 oil? Are there negatives to this idea for hot weather running?

    Cheers

    Alec
    Hi Alex,
    IMHO no normal engine should have to use 20w-60 oil. I have had stuffed engines in the past and never went that high. Not sure why they sell it actually.

    Really all those old engines were designed for 30 weight oil. That was the standard for normal use, modified by the climate if you lived in 'severe' temperatures. Never lived there so have little knowledge We seem to have retained 30 as the top weight for all new petrol engines anyway and for diesels it is 40.

    Regarding the oil light flickering on at idle. That was considered normal on most older cars as they wore a bit, when hot and idleing but it should go out when the revs rise a bit. Noting the oil then was not multi grade as now. A multigrade oil should help with restricting the viscosity reduction when hot. That's why we have it
    Jaahn
    Last edited by jaahn; 23rd September 2015 at 01:35 PM.

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    Thanks for your insight Jaahn. It might be worth noting the engine burns almost no oil...maybe a quart every oil change (3000 miles for me) so the fact that it's flickering as a "new" engine with multi-vis is concerning. Still going to get an actual gauge on the pressure and see what's up with it.
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    Quote Originally Posted by pynhead View Post
    Thanks for your insight Jaahn. It might be worth noting the engine burns almost no oil...maybe a quart every oil change (3000 miles for me) so the fact that it's flickering as a "new" engine with multi-vis is concerning. Still going to get an actual gauge on the pressure and see what's up with it.
    Oil consumption and low pressure when hot are not related. Oil usage comes, typically, from bad valve stem seals, worn rings or a combination of those problems. Low oil pressure, when the engine is hot, is going to be either a pump problem, excessive gap between sleeve bearings and the journals or a combination of both. In any case it should not be happening with a 'totally' rebuilt engine with about 10K on it. And a worn pump will normally exhibit a lower than normal pressure when the engine is cold.
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    It could be the oil pressure switch. I had one go on a Citroen BX that must have got a small crack in its diaphragm. Was OK to start with but as oil pressure leaked to behind the diaphragm, it would start to switch at higher and higher oil pressure until it was on all the time. So drives of 15 minutes or less were OK - longer and lots of meep morp noises. Then it would reset with the engine turned off. I suppose if there were a small leak from the back of the diaphragm to outside then you might get a more consistent back-pressure after some running so it would rise form triggering at say 10 psi to 30 psi which might give you the symptoms you are experiencing.

    Just a thought.

    Ken
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    change the oil pressure switch!!! I bet it's leaking if you check
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    I had one of those worry lights flickering once due to some crud that lodged up its spout. I fitted a gauge, back in 1974, to diagnose - this demonstrated that there was no problem. It still sits on 58-60 psi hot above about 2000 rpm and an absolute minimum of 25 psi when very hot and idling at 800 rpm. Renault R8 but same principle. Cleaned the sensor tube and it has been perfect ever since too.

    Cheers
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    Quote Originally Posted by pynhead View Post
    Thanks for your insight Jaahn. It might be worth noting the engine burns almost no oil...maybe a quart every oil change (3000 miles for me) so the fact that it's flickering as a "new" engine with multi-vis is concerning. Still going to get an actual gauge on the pressure and see what's up with it.
    Was it a new oil pump also???

    I know one of my engines gives crap idle pressure and I'm kicking myself for not replacing the oil pump whilst the engine was on the stand.

    Jo

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    Now go make me a sandwich Hotrodelectric's Avatar
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    Ignore the oil pressure switch at your peril. It's a well-known fault and once it fails, it fails catastrophically. If it's leaking do not delay- replace it. It's located on the engine just above the fuel pump on the driver side (sorry Australia- our driver side) of the engine. Hein can do the replacement if you can't.

    This has nothing to do with variable oil pressure as Steve throughly notes, but this is such a common failure point that any D owner should be watching for it anyway, regardless of how many miles are on the rebuild.
    The measure of your character isn't what you do when people are watching- it's what you do when they aren't watching.

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    Jo,

    Unfortunately i don't have the parts list on the engine rebuild. The previous owner (who was fastidious in some regards and completely negligent in others) had it rebuilt by Peter Koine in the Bay Area. I always assumed that any part that would be an obvious "while you are at it..." was dealt with during the rebuild but it could be the original oil pump.

    I've been coordinating with Wally to schedule a front brake disc replacement surgery...but given this conversation I'm thinking I should probably decommission the car until it's ready to go under the knife and give it a complete going-over.

    I appreciate the feedback gents
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    Quote Originally Posted by pynhead View Post
    Jo,

    Unfortunately i don't have the parts list on the engine rebuild. The previous owner (who was fastidious in some regards and completely negligent in others) had it rebuilt by Peter Koine in the Bay Area. I always assumed that any part that would be an obvious "while you are at it..." was dealt with during the rebuild but it could be the original oil pump.

    I've been coordinating with Wally to schedule a front brake disc replacement surgery...but given this conversation I'm thinking I should probably decommission the car until it's ready to go under the knife and give it a complete going-over.

    I appreciate the feedback gents
    If Peter did the rebuild then you can be certain that it was done correctly. But as Bill and others have said - check the oil pressure switch with a gauge. Even if new, have seen them fail right out of the box. Not too often, but enough times that I carry a couple of spares with me in my D's.

    Steve

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    Perfect Steve...I ordered the switch today.
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    who told you hey were going to cut it with a knife?

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    Quote Originally Posted by Citroenfan View Post
    If Peter did the rebuild then you can be certain that it was done correctly. But as Bill and others have said - check the oil pressure switch with a gauge. Even if new, have seen them fail right out of the box. Not too often, but enough times that I carry a couple of spares with me in my D's.

    Steve
    +1 on that. Peter is highly regarded. Possible it is the original pump, just so long as it met spacs. Dumb question time: when was the last oil change done? Those arrows on the filter cartridge and the sump are supposed to be lined up perfectly. If not, you might experience some trouble with oil delivery.

    Steve, remember that list we were working through to remember who all is left out here to work on this stuff? Yah- he's one of them.
    The measure of your character isn't what you do when people are watching- it's what you do when they aren't watching.

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    I replaced the oil switch and the oil pressure light is behaving in the same manner. So much for the path of least resistance fix.

    Moving to the next step in the process of elimination while keeping my fingers crossed the issue is not something more invasive.

    As the oil/engine heats up (and the oil becomes less viscous) the warning light comes on at idle. I suppose it could also be a byproduct of some metal expansion within the engine as well (more concerning)

    Much to my surprise...the oil i'm currently using turns out to be 5W-50 (instead of 20W-50 as i originally thought) so i'm going to do quick change back to 20W-50 and confirm the arrows are aligned, replace the filter cartridge and see if the light warning continues.

    Beyond that...i guess I'll just take one step at a time and not worry about the next step until i need to take the next step.
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    Quote Originally Posted by pynhead View Post
    I replaced the oil switch and the oil pressure light is behaving in the same manner. So much for the path of least resistance fix.

    Moving to the next step in the process of elimination while keeping my fingers crossed the issue is not something more invasive.

    As the oil/engine heats up (and the oil becomes less viscous) the warning light comes on at idle. I suppose it could also be a byproduct of some metal expansion within the engine as well (more concerning)

    Much to my surprise...the oil i'm currently using turns out to be 5W-50 (instead of 20W-50 as i originally thought) so i'm going to do quick change back to 20W-50 and confirm the arrows are aligned, replace the filter cartridge and see if the light warning continues.

    Beyond that...i guess I'll just take one step at a time and not worry about the next step until i need to take the next step.
    Yah, 5W50 is a bit thin for an older French car. They love 20W50. I forget- are you running a synthetic? Synthetics will run a little freer-flowing than standard dino oil. And don't run any of the cheap no-names you normally find at AutoZone or PepBoys. Castrol/Quaker State/Pennzoil, or from any of the major oil companies like Shell or Mobil.

    When you do change your oil, make 100% certain the arrows on the sump and the filter cartridge are aligned. If not, there will be a disaster on your hands.

    No guys, we don't see Total or Agip over here and Fina is extremely rare in SoCal.
    The measure of your character isn't what you do when people are watching- it's what you do when they aren't watching.

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    Wow...situation seems to be resolved.

    I replaced the oil and filter (both with only 800 miles of use) and the oil pressure appears to be 100% normal.

    It's 95 fahrenheit in LA today and i drove it for an hour with engine temps bumping up against the danger zone without any warning light activity at idle.

    Now i guess i need to do some deductive reasoning to figure out what it could have been?

    The 5W-50 (Castrol Synthetic) was still reasonably fresh so i find it hard to believe it's already broken down to the point that it loses all viscosity? It looked clean and reasonably clear.

    The filter looked pretty dirty but i'm sure that would be the case regardless of how long it's used....it just looks used and there's nothing abnormal in the filter media that would indicate anything unusual.

    The arrows were perfectly aligned when i removed the plate so i returned them to the same location upon replacing the filter.

    It's hard to draw any other conclusion other than the 5W-50 is just too thin for the DS motor (or at least my motor) while operating under higher temperatures. I replaced the oil with conventional 20w-50 and i'm guessing i'll be sticking with that from this point forward.

    I'm pleased the problem seems to have been solved at this stage...the next stage would have been much more involved.

    Thanks for the tips!
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    Now go make me a sandwich Hotrodelectric's Avatar
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    I doubt the Castrol broke down enough to cause your problem. Castrol is a quality product, and synthetics are excellent at wear resistance. I really think it was simply too thin an oil for the use. Fortunately, you experienced no genuine failure.

    By the way, if you can make it, bring that beast by Best of France and Italy car show- Nov 2, I think. Woodley Park in Van Nuys.
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    Glad to hear the oil change fixed it. I expect quite a few of us out in cyberland expected that - 5W is pretty light for a warm city. I don't think anyone in Oz would use anything lighter than 20W-50. In the old days it was, for example, Castrol XL, which was 20W-30-40.

    Think of it as an engine flush perhaps....

    Love the avatar - Big Sur?
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    Now go make me a sandwich Hotrodelectric's Avatar
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    Quote Originally Posted by JohnW View Post
    Glad to hear the oil change fixed it. I expect quite a few of us out in cyberland expected that - 5W is pretty light for a warm city. I don't think anyone in Oz would use anything lighter than 20W-50. In the old days it was, for example, Castrol XL, which was 20W-30-40.

    Think of it as an engine flush perhaps....

    Love the avatar - Big Sur?
    A lot of the newer cars spec something absurdly thin, like 5W15 or even 5W10. It's all in the name of attaining lower resistance, with better fuel economy at the end, overall reliability be damned.
    The measure of your character isn't what you do when people are watching- it's what you do when they aren't watching.

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    I'll definitely be at the show Hotrodelectric...missed you there last year! I never really thought a 5W-50 would perform substantially different from 20W-50 but there you have it. I guess oil viscosity is not a myth afterall

    Thanks everyone....

    and yes JohnW that shot was in Big Sur! Here's a larger version of it.

    Oil Pressure Light + Hot Weather = Neurosis?-dsc_0230.jpg
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