Low engine oil pressure light on at idle - JeepForum.com
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post #1 of 33 Old 02-16-2019, 04:12 PM Thread Starter
alberto68888
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Low engine oil pressure light on at idle

Hello everyone, im a owner of a WK 08 4.7 with 60k miles on the clock. it all started with a bad radiator, i did replace it with a new one and new upper, lower hose and thermostat. But while driving, the upper hose clamp fail causing a overheating issue tow it back home, put a new upper hose clamp in and drove it for a fews weeks until i realized that coolant was gone, bad head gasket due to overheat...

Took it to a shop to replace all gasket but the shop told me that it would need to resurface the heads. When everything was assambled, the low oil pressure lights on when engine reach operative temp, and a noise started coming from the timing chains ONLY when engine reach operative temp. The shop said it is a bad timing chain but i didnt believe them because before droping the truck at shop there wasnt any weird noises coming from engine. So i tow it back home again.

The thing is the light and the noise will only appears if engine is hot and revs between 500-700 rpms. If i rev above that, like 1000+ rpms the light will turn off and the timing chain noise will desappear. I thought it could be a oil viscosity issue so tried putting a 10w30 in (always run 5w20) but nothing changes.

Could be a bad oil pump? But they didnt have to reach to the oil pump for taking out the heads and resurfacing them i think. I dont want to take it to a shop because everyone is telling me to change the timing chain and tensioners but i dont think that will solve the issue.

P.D: My english is kind a poor, my apologizes.

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post #2 of 33 Old 02-16-2019, 08:11 PM
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Your English is fine!


With a pump driven off the timing change (directly or indirectly), you can get erratic operation leading to low pressure at low RPMs. Timing chains tend to act up more at low RPM than high, because the lower the RPM's, the more pressure on the poor cam.



I don't think this is the case, because the 4.7 pump is driven off the crank shaft.


If I had to guess at it, I'd say the sensor. The gear type pumps are very reliable. The only way I know of to verify the sensor is by replacement or the test below.



It might not be a bad idea to get the oil pan off and inspect the oil pickup screen. If it's like most screens I've seen, there is a bypass valve for if the screen clogs (it would then open and allow oil to flow around the screen). It's like a small round door and is spring loaded. I've seen them stuck open from dirt. I suppose one could be just stiff and not open up until there is more force and cause the low pressure problem.



Of course replacing the oil filter might not be a bad idea.



Testing:


1. Remove oil pressure sending unit and install gauge
assembly C-3292.
2. Run engine until thermostat opens.
3. Oil Pressure:
• Curb Idle—25 Kpa (4 psi) minimum
• 3000 rpm—170 - 550 KPa (25 - 80 psi)
4. If oil pressure is 0 at idle, shut off engine. Check
for a clogged oil pick-up screen or a pressure relief
valve stuck open.


Operation:


Oil from the oil pan is pumped by a gerotor type oil pump directly mounted to the crankshaft nose. Oil pressure is
controlled by a relief valve mounted inside the oil pump housing.
The camshaft exhaust valve lobes and rocker arms are lubricated through a small hole in the rocker arm; oil flows
through the lash adjuster then through the rocker arm and onto the camshaft lobe. Due to the orentation of the
rocker arm, the camshaft intake lobes are not lubed in the same manner as the exhaust lobes. The intake lobes are
lubed through internal passages in the camshaft. Oil flows through a bore in the number 3 camshaft bearing bore,
and as the camshaft turns, a hole in the camshaft aligns with the hole in the camshaft bore allowing engine oil to
enter the camshaft tube. The oil then exits through 1.6mm (0.063 in.) holes drilled into the intake lobes, lubricating
the lobes and the rocker arms.


This also seems to indicate it's not a timing chain issue:
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post #3 of 33 Old 02-18-2019, 07:04 PM Thread Starter
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I dont think it could be a bad oil pressure sensor, that wont explain the noise coming from the timing chain at idle with the engine is hot.

Mechanic said the noise is due to a bad hydraulic chain tensioner. But those tensioner works with oil pressure, so the noise and the low pressure are related.

What i find kinda weird is that all this happens after the gasket/resurfacing job. But they didnt have to mess with the oil pump in order to get the job done... They also put new oil (Pennzoil 5w20 full synthetic) and oil filter, which i provided to them. I got to take a look to the oil filter or maybe just change it anyways, aswell as droping the carter to see if the oil pickup screen is clogged. Should i replace the carter gasket while doing this?

I tried to dismount the oil engine pressure sensore but it was hard to reach. Any suggest about how to get to it?

Last edited by alberto68888; 02-18-2019 at 07:04 PM. Reason: Grammar
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post #4 of 33 Old 02-18-2019, 08:27 PM
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Hi Alberto, after posting I found a picture of the oil pickup screen, and it has a cover over most of the screen. You can't see the valve according to that picture.



I can't imagine they contaminated the oil enough to cause the problem, but I guess it's possible. Maybe drain a small amount into a clean container and see if it is clean?



Keep in mind there could be two separate problems. From what you wrote it sure seems like you have low oil pressure and that is causing the tensioner to be weak at low RPM's.

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post #5 of 33 Old 02-19-2019, 08:02 AM
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Many good suggestions already. I have the same engine.

Possible causes:
1. Low on oil - easy to check
2. Bad oil pressure switch - probably not.
3. Bad oil pump - probably not with only 60,000 miles
4. Issue with timing chain adjusters - it is possible that they were not installed correctly when replacing the heads. The result is a loss in oil pressure. Reason I mention this is that the oil pressure problem did not exist prior to removing the heads - possible.
5. Issue with valve lash adjusters - it is possible that during the head gasket replacement process they did something to the lash adjusters which may have dropped the oil pressure. Reason I mention this is that the oil pressure problem did not exist prior to resurfacing the head - possible.
6. Badly worn crank bearings due to too much coolant entering the engine from the bad head gasket - possible.

What I would do:
A. check oil level to make sure it is correct
B. attach an oil pressure gauge at the oil pressure switch to check oil pressure to see that it is within specification.

If oil pressure is confirmed bad you will most likely need to either install new timing belt adjusters, change out the heads, rebuild that engine, or replace the engine. You could pull the oil pan and clean the oil intake screen as a last resort but I would not count on that being the problem because you mentioned that the oil pressure light goes off when the engine runs at higher rpms. A screen clog does not improve with rpms.
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post #6 of 33 Old 02-19-2019, 05:59 PM Thread Starter
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Quote:
Originally Posted by BadExample View Post
Hi Alberto, after posting I found a picture of the oil pickup screen, and it has a cover over most of the screen. You can't see the valve according to that picture.



I can't imagine they contaminated the oil enough to cause the problem, but I guess it's possible. Maybe drain a small amount into a clean container and see if it is clean?



Keep in mind there could be two separate problems. From what you wrote it sure seems like you have low oil pressure and that is causing the tensioner to be weak at low RPM's.
When i did the oil swap with 10W30, the drained oil seems quiet darker than it should, it has nearly 50 miles on it. Thank you for your suggestions i will take a look to the carter as soon as i can.

Quote:
Originally Posted by RCS1300 View Post
Many good suggestions already. I have the same engine.

Possible causes:
1. Low on oil - easy to check
2. Bad oil pressure switch - probably not.
3. Bad oil pump - probably not with only 60,000 miles
4. Issue with timing chain adjusters - it is possible that they were not installed correctly when replacing the heads. The result is a loss in oil pressure. Reason I mention this is that the oil pressure problem did not exist prior to removing the heads - possible.
5. Issue with valve lash adjusters - it is possible that during the head gasket replacement process they did something to the lash adjusters which may have dropped the oil pressure. Reason I mention this is that the oil pressure problem did not exist prior to resurfacing the head - possible.
6. Badly worn crank bearings due to too much coolant entering the engine from the bad head gasket - possible.

What I would do:
A. check oil level to make sure it is correct
B. attach an oil pressure gauge at the oil pressure switch to check oil pressure to see that it is within specification.

If oil pressure is confirmed bad you will most likely need to either install new timing belt adjusters, change out the heads, rebuild that engine, or replace the engine. You could pull the oil pan and clean the oil intake screen as a last resort but I would not count on that being the problem because you mentioned that the oil pressure light goes off when the engine runs at higher rpms. A screen clog does not improve with rpms.
The engine oil level is ok, it sit in the middle of "SAFE" on the dipstick. First time i noticed the noise they took off everything to double check, i did saw the tensioner and one of them (the ones that runs with the camshaft chain) seems a little loose but the other side was ok. When they turn the crankshaft it will loose the other one and the one that was loose will tense. And with that, they said the whole timing kit must be replaced.

About the valve lash adjuster, if there is something gone bad, should not be making some noise on top of the heads? And the coolant issue was not that bad. Added almost 1 galon every 2 week, about 200 miles. There was no milky oil, only a smoking exhaust and the engine was running hotter, in between the middle mark and the next one in the temp gauge. Monitoring with a scanner i think it was around 110ºC degrees but cannot remember how much exactly.
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post #7 of 33 Old 02-19-2019, 06:45 PM
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That doesn't sound terribly overheated to me. I hope you get it sorted!

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post #8 of 33 Old 02-20-2019, 09:25 AM
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Quote:
Originally Posted by alberto68888 View Post
When i did the oil swap with 10W30, the drained oil seems quiet darker than it should, it has nearly 50 miles on it. Thank you for your suggestions i will take a look to the carter as soon as i can.



The engine oil level is ok, it sit in the middle of "SAFE" on the dipstick. First time i noticed the noise they took off everything to double check, i did saw the tensioner and one of them (the ones that runs with the camshaft chain) seems a little loose but the other side was ok. When they turn the crankshaft it will loose the other one and the one that was loose will tense. And with that, they said the whole timing kit must be replaced.

About the valve lash adjuster, if there is something gone bad, should not be making some noise on top of the heads? And the coolant issue was not that bad. Added almost 1 galon every 2 week, about 200 miles. There was no milky oil, only a smoking exhaust and the engine was running hotter, in between the middle mark and the next one in the temp gauge. Monitoring with a scanner i think it was around 110ºC degrees but cannot remember how much exactly.
I re-read your initial post. I go back to the comment that - The shop that did the re-surfacing of the heads and head gasket replacement said that you needed new timing chains. Why would they say that unless they know that they created a problem.

No way do you need new timing chains with only 60,000 miles. My bet, and it is only a guess, is that the shop knew you needed new chain adjusters when they re-assembled the engine but decided not to install them for whatever reason. If the shop is going to take the timing cover off anyway, I would put in the new timing chains. In the United States, a Mopar timing chain kit costs about $250 - last time I did mine about two years ago. Good luck with this!
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post #9 of 33 Old 02-20-2019, 12:56 PM Thread Starter
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Quote:
Originally Posted by BadExample View Post
That doesn't sound terribly overheated to me. I hope you get it sorted!
It was not that bad, the only damage i can tell is the head gasket. After replacing the hose clamp i did drove it a while until i decided to tackle the gasket issue. Thank you for your guidance.

Quote:
Originally Posted by RCS1300 View Post
I re-read your initial post. I go back to the comment that - The shop that did the re-surfacing of the heads and head gasket replacement said that you needed new timing chains. Why would they say that unless they know that they created a problem.

No way do you need new timing chains with only 60,000 miles. My bet, and it is only a guess, is that the shop knew you needed new chain adjusters when they re-assembled the engine but decided not to install them for whatever reason. If the shop is going to take the timing cover off anyway, I would put in the new timing chains. In the United States, a Mopar timing chain kit costs about $250 - last time I did mine about two years ago. Good luck with this!
Indeed, the shop said first i must replace the whole thing. When i asked why, they came up with something like "When you resurface the heads, the materials taken out will make the head thinner than it was originally so the chains will be loose". I know, when you resurface you need to clean all the surface by taken out materials and sharpen the head, but i think the difference will not be noticeable, almost negible about the chains. They wont have to chop the heads half or cut 1" out in order to do that, right?

I argue with them about that and they just said at least i will need to replace the tensioners. But i did not trust them anymore so i tow the truck back home.

The first thought i got was the low pressure cause the noise from the timing chains, that the tensioners was not working properly because of that. But could it be on the contrary, could be a bad tensioner cause the low oil pressure issue?
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post #10 of 33 Old 02-20-2019, 02:51 PM
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Quote:
Originally Posted by alberto68888 View Post
It was not that bad, the only damage i can tell is the head gasket. After replacing the hose clamp i did drove it a while until i decided to tackle the gasket issue. Thank you for your guidance.



Indeed, the shop said first i must replace the whole thing. When i asked why, they came up with something like "When you resurface the heads, the materials taken out will make the head thinner than it was originally so the chains will be loose". I know, when you resurface you need to clean all the surface by taken out materials and sharpen the head, but i think the difference will not be noticeable, almost negible about the chains. They wont have to chop the heads half or cut 1" out in order to do that, right?

I argue with them about that and they just said at least i will need to replace the tensioners. But i did not trust them anymore so i tow the truck back home.

The first thought i got was the low pressure cause the noise from the timing chains, that the tensioners was not working properly because of that. But could it be on the contrary, could be a bad tensioner cause the low oil pressure issue?
Engine head resurfacing will NOT affect the timing chain.

It does sound like they removed the timing chains to fix the head gaskets. Yes, when you take off the timing chains you should put in new timing chain tensioners - if I recall correctly, there are two of them and there is a special piece that has to be placed beneath one of them when installing. Purchase Mopar chain tensioners because removing and replacing the timing cover takes lots of time and you do not want to do it twice.

New timing chain tensioners may or may not fix your low oil pressure problem. But, when taking off the timing chains, installing new tensioners is a very good idea. The shop could have installed the old ones incorrectly and that is where you could be losing oil pressure at idle.

The video below shows you the two tensioners. At 9:30 the guys in the video show how the tensioners work with the oil.

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post #11 of 33 Old 02-20-2019, 07:20 PM
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@alberto68888 Happy to take a jab at helping. I am not familiar enough with these engines (yet) to make definitive judgments as to what might be wrong. So I tried to give you some help based on past experience, general theory and what I've read. It really does sound like the shop is not honest and maybe trying to cover their own induced faults or failure to identify problems while disassembled.


@RCS1300 cool video!

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post #12 of 33 Old 02-23-2019, 07:50 PM Thread Starter
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Engine head resurfacing will NOT affect the timing chain.

It does sound like they removed the timing chains to fix the head gaskets. Yes, when you take off the timing chains you should put in new timing chain tensioners - if I recall correctly, there are two of them and there is a special piece that has to be placed beneath one of them when installing. Purchase Mopar chain tensioners because removing and replacing the timing cover takes lots of time and you do not want to do it twice.

New timing chain tensioners may or may not fix your low oil pressure problem. But, when taking off the timing chains, installing new tensioners is a very good idea. The shop could have installed the old ones incorrectly and that is where you could be losing oil pressure at idle.

The video below shows you the two tensioners. At 9:30 the guys in the video show how the tensioners work with the oil.

https://www.youtube.com/watch?v=-zjrh1WYAgM
I believe that the timing chains must be removed in order to take off the heads, if im not wrong. Are u sure about the tensioners replacement been a must to replace after taking the chains off? If so, there should be the problem because i did not replace them after all.
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post #13 of 33 Old 02-24-2019, 10:30 AM
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Quote:
Originally Posted by alberto68888 View Post
I believe that the timing chains must be removed in order to take off the heads, if im not wrong. Are u sure about the tensioners replacement been a must to replace after taking the chains off? If so, there should be the problem because i did not replace them after all.
The timing chains do not need to be removed when removing the heads. There is a spacer that one can use to keep the top two chains in place while removing the heads. It is a special tool made for this engine for this purpose. I have one. I decided to change my chains and tensioners when I removed and replaced my heads because I was deep into the engine and I had about 80,000 miles.

One can re-use the old chain tensioners and it may work. They can be collapsed in a vice and have the pins re-inserted. I would never do that but some people might.

Based on your initial post in this thread it seemed like you did not have this oil pressure problem before the shop worked on your vehicle. If that is correct, it is likely that something that they did or did not do is causing the problem with the oil pressure.
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post #14 of 33 Old 02-24-2019, 12:49 PM Thread Starter
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Well i think they did not have that tool. They did mess with the chains for taking the head off...

Yes, the pressure issue begin after the job. My primary suspect was the oil pump but dont know if they took it off.

Im aware that they did:

- Head gasket replace.
- Resurface heads.
- Oil and filter change.
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post #15 of 33 Old 02-24-2019, 01:24 PM
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Quote:
Originally Posted by alberto68888 View Post
Well i think they did not have that tool. They did mess with the chains for taking the head off...

Yes, the pressure issue begin after the job. My primary suspect was the oil pump but dont know if they took it off.

Im aware that they did:

- Head gasket replace.
- Resurface heads.
- Oil and filter change.
Based on that information, I am fairly certain that they did not touch the oil pump.
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