noise."Mechanic: Oil Pressure · 3:06am Mar 30th, 2022
Alright kids, get your favorite drink and settle in!
This one’s short and has a video!
To set the scene, we’ve got a 2015 or so Jeep Compass with a 2.4L motor. It’s your typical early teens engine, with variable valve timing, and the customer just bought it.
A month ago or thereabouts we fixed its first problem. The crank sensor didn’t work—I’ve covered those crank sensors in other blogs. Diagnosis on this one was simple; not only was it missing the heat shield, but the wires to the crank sensor were broken. A new wiring pigtail, crank sensor (for good measure, they’re cheap), and heat shield fixed it right up.
Well, almost. It came back later with the check engine light on again.
This time around it wasn’t the crank code; instead, it would set either a P000A or P000B code, or both*. Those are slow response/no response codes for the variable cam timing. Some automakers add symptoms to the code (which I have also discussed before) but Chrysler can’t be bothered.
I’m trying to keep this one short (we’ll see how that goes), so I won’t go into great detail about variable valve timing. What you need to know is that a phaser on the end of the camshaft(s) can change the camshaft angle as desired for various reasons. Oil is fed through an oil control solenoid to the phaser to advance or retard it. Since on startup there is no oil pressure, a spring-loaded pin in the phaser holds the camshafts in a fixed position until there’s enough oil pressure to operate the variable cam timing.
Source
(in the illustration, the ‘fluted variator’ is the phaser and the ‘control unit’ is the solenoid)
The code implies that either they don’t move at all, or that they do move, but not as fast as the computer thinks they should.
Chrysler’s diagnostics, as reported by Identifix, suggest that you should clear the codes, test-drive, and see if they come back. If they do, test to make sure that the solenoids are getting power and ground from the PCM; if they are, replace the solenoids and re-test. If the solenoids didn’t fix it, the computer’s bad.
You may already be thinking they’re skipping a step (and they are), but we’ll get back to that.
The solenoids are getting power and ground when commanded, and the screens aren’t plugged with debris [they’ve got screens to keep debris out]. Per the diagnostics we replaced them, although my manager and I both thought that wouldn’t fix it, and it didn’t.
Since this vehicle is new to the customer, we don’t know its history, but it’s giving off the vibe of a vehicle that wasn’t well-maintained. Sludge and stuff can build up inside the phasers and impede their movement, and that can be flushed out (sometimes) by cycling the solenoids quickly. On Ford and GM products, that’s accomplished by tapping a wire against one of the terminals while the engine is running, whereas Chrysler actually has a procedure on the scan tool that makes the PCM do it. It works, in the sense that you can hear the solenoids operating and the engine not being happy with its cam timing going crazy at idle. It does not make the code go away.
So the next plan is to replace the phasers. Maybe they’re too gummed up to be saved, and since we have to take the timing chain off to replace them, it would be stupid to not replace it.
Already I’ve got my doubts; we’ve been burned before with cam timing on a poorly-maintained engine; there are lots of tiny, critical oil passages that might be clogged, and no way of ever knowing. Smart move is put an engine in it, but the customer has an aftermarket warranty and they won’t spring for that just based on technician experience.
Maybe if we make it toss a piston through the block, they will. . . .
Tearing into it, my worst fears are realized; the upper end is badly sludged up. What can’t I see? No way to know. The thing sits for two weeks torn apart, because the parts that Chrysler was supposed to deliver don’t arrive and we’ve got a bazillion other projects to deal with once they finally have. I’m sure that the customer is getting upset that her shiny new (to her) Jeep is sitting in the shop on life support.
She finally got it back and enjoyed it for a whole weekend and then the check engine light came back on and to my complete lack of surprise it’s a cam code again.
Mitchell ProDemand, our other main shop resource, has a slightly different method of testing for this code. They suggest testing the oil pressure up top, at the oil temperature sensor, which is in the oil passage that feeds the VVT solenoids. Low pressure there will make them inoperable, regardless of how good the wires, PCM, solenoids, and phasers are. So we try that, and it’s kind of okay in the shop.
Mitchell also mentions that there’s a filter screen in the oil passage to keep debris out of the VVT system, and it can be changed. I propose that the screen might be clogged, and even if the pressure’s good, the volume might not be.
[I should also mention as an aside, that Chrysler’s spec for oil pressure at idle is 4psi, which is stupid. I can now tell you (from testing and other things) that it has 60psi at idle, which seems far more reasonable.]
Because I thought that clogged oil passages (or screen) could cause the oil pressure at the bottom of the engine to be okay when it was very much not okay at the top, we put two oil pressure gauges on it. I’m expecting the top one to be lower than the bottom one, but not by much.
At first they were mostly the same, and everything worked, and then I drove it for a while, and things got bad.
The gauge on the right is reading oil pressure at the filter, and it’s around 50psi. The left gauge is reading pressure at the feed to the VVT (above the screen), and it should be similar to the other gauge. Instead, it’s reading about zero. The VVT isn’t working anymore, and it has set a P000A code.
We tried to flush it out with clever adapters, but that failed. A bunch of debris did come out, but it wasn’t enough to get the system working again. Our next step is replace the screen. The good news is that that’s probably a cheap part (I don’t know for sure, but I bet it’s under $20). The bad news is that you have to take off the cylinder head to replace it.
*Maybe in a longer blog post I’ll get to this, but in a nutshell certain failures block other tests. In this case, I would assume that the engine had VVT problems before the customer bought it, but since the crank sensor has malfunctioned, it will not operate (nor test) the VVT system. I don’t want to accuse the dealership who sold her the car of anything—they might have bought it at auction, shined it up, and sold it ‘as is’ with a check engine light on—but if you knew you had a car with this problem, you could break a wire or two on the crank sensor harness, have it set a different code that requires a cheap-to-replace part, and even if the customer was smart enough to have the codes scanned before agreeing to buy the car, they would not discover the more serious issue the engine has.
I also didn’t mention in the blog, but the same oil passage that provides the oil that the VVT system uses to operate also lubricates the camshafts . The Jeep can operate just fine (mostly) without functioning VVT, but it can’t operate for too long with little to no oil flow to the cam bearings.
When you flush it and stuff comes out, thats a *bad* sign.
5647163
When you flush an assembled and recently running engine and stuff comes out, that's a really, Really bad sign.
When you run a recently assemble engine and coolant water comes blasting out the oil filler header pipe, then theres something seriously wrong?
Am I crazy for trying to design a compacy multicylnder ship engine, that you can shut parts down to work on for repairs while the rest of the engine is still running, incase the robotc maintenance system cant do the job on the still moving machinery?
Given surgical robot in the lab has operated on a beating heart?
I love that word "solenoid."
Makes you want to try switching SCE to Aux and save the day after a lightning strike hits your vapor column. Or piping the modulus to standard output and grepping the largest prime. Or converting mAh to farads for fun.
Fun, fun. Today I need to keep trying to figure out what in an early 00's GMC pickup is draining the battery, and how a solenoid operated hydraulic valve reversed its function (runs the discharge chute on a feed mixer truck, for some reason now applying power turns the chute off... which means the switch gets left on overnight. And again, drained battery...)
Oh, and an easy one. Weld up a cracking 3.5 yard capacity loader bucket where a seam is pulling apart.
I'm not a mechanic, I just try to hum along off-key...
5647187
What? Doesn't every auto mechanic have a 20L bioti-nanite bath for immersion cleaning of entire engines inside and out? What is this? Not 2122 AD?
got to love Chrysler jeep / just enough extra parts. total junk.
5647163
I would argue that when flushing a system having nothing at all come out is worse
5647266 Particularly when talking medical terms.
"I don't understand. I took all the medications the doctor said for my colonoscopy, and I drank like a gallon of Gatorade. Maybe a second gallon..."
At least it's not a Chrysler 2.7L? (Fun thing, a 3.2L will actually work using the ECU off a 2.7L, plus then you don't need to deal with any of that sentry key garbage that all the used 3.2L ECUs always look for and that vehicles with a 2.7L generally don't have most of the wiring/components installed for.)
I'd say that they need to bring back the 4.0L I6, but I'm sure that there's some dumb annoying reason that they won't (or possibly even can't).
Took me too long to realise that the asterisk was in the comments.
I hate those problems that are like this - have something not work, see a broken thing, fix the broken thing (finally after the parts arrive) .. and then the widget still isn't working and you have to work on the next broken thing.
Got something similar at work - 4 different vendors, something changed in february, and we're still lodging cases and uploading logs. Should be fixed sometime (checks watch) Mayish?
images-ext-1.discordapp.net/external/84i7BzsEgXQVCgzW5jRpzyJZ-PwNl56_qqc0eJnyqQA/%3F_nc_cat%3D106%26ccb%3D1-5%26_nc_sid%3D730e14%26_nc_ohc%3D1oVPr9nBN60AX8_LgAc%26_nc_ht%3Dscontent-sea1-1.xx%26oh%3D00_AT-jRnhkGmwK5u1xeyEq43QVndfoF-S8cNUWAAwrkqjI6g%26oe%3D626AAB09/https/scontent-sea1-1.xx.fbcdn.net/v/t1.6435-9/56323785_589165311593415_7498281465885491200_n.jpg?width=513&height=683
5647163
5647187
The engine is creating its own glitter!
derpicdn.net/img/view/2021/8/15/2678884.png
5647586
Yeah powertrain glitter is nothing but expensive. And usually catastrophic.
5647163
When you know it’s in there, though, that’s kind of what you want (for the stuff to come out). Although really at this point, we were grasping at straws. Would have been better if there wasn’t any blockages in the oil passages.
5647167
Wait until I tell you about the 5.3L I’m putting a lifter in. It’s a GM crate motor with nearly 10,000 miles on it, and one of the lifters collapsed.
Admittedly, it ran longer than the Suburban’s GM crate motor, which malfunctioned moments after its first startup, and now I check all reman motors to make sure the assembler didn’t leave any extra bolts in the intake runners.
5647187
Especially if it’s glittery. Or whole chunks of metal, that’s really bad.
5647212
We had a worn-out engine that did that. It was cool enough that the engine got started so every mechanic could witness the coolant shooting out of the dipstick tube. That’s not something you see every day!
Your big problem is the crankshaft IMHO. Solve that and you’re golden. Some industrial engines (like the locomotive engine above) you can replace each cylinder head individually and they also have petcocks you can open to let the compression out (or drain the water that might gather inside after a long shutdown).
In theory, you could build a robot that could do some engine repairs with the engine running. The trick would be having it in the right place when needed.
5647224
That’s a good word. Although I have to say that based on the diagram of the VVT system I posted, I like ‘fluted variator’ better than ‘phaser.’
. . . I don’t know what any of that is.
5647228
For the first, there is a way you can check fuses for draw without pulling anything off the vehicle. I’d have to go digging, but VW actually has pages and pages of charts for that, including calculation tables for how many amps that fuse in particular is passing. Or if you’ve got a thermal imager, you can leave it overnight (hopefully on a cold night) with a fully-charged battery or even a battery charger on trickle, and then see what’s warm in the morning.
No idea on the solenoid, unless it’s something that can overcenter and run backwards if it does.
We had a Saturn Vue in today that looked nice on top, and then underneath the frame’s got holes in it. One of the suspension mounts is starting to pull off the body, and there’s really no fix for that.
5647244
I wish we did.
We can get “universal engine solvent” and soak everything in that when the head’s off. It’s kind of dangerous and a fire hazard, but gasoline dissolves most engine deposits, and if we fill the thing to the top, in theory that’ll dissolve all the engine deposits. It’s the only option besides tearing down the whole engine. [The flush attempt that failed was mostly gasoline with some boosters added in for extra efficacy.]
5647247
Funnily enough, most of the cars we get with timing problems are GM . . . I’ve never had to replace VVT components on a Chrysler product before. This thing’s biggest problem is lack of maintenance, and since the customer bought it used, she couldn’t have known what the inside of the engine looked like.
5647266
Depending on what we’re after, yeah, that would be worse. Flushing heater cores, you want to see the chunks, ‘cause that means they’re not in the heater core any more and maybe it’ll work now.
5647300
And what happens next is going to be an event. Probably in technicolor, if Gatorade was involved. Also you might be banned from ever visiting that doctor again, and spoken of in whispers for decades to come.
5647425
That was an engine that existed, and I’m not sorry that it’s gone now.
Yeah, the ECU thing is an advantage of parts interchangeability. We found out (by accident) that if you put a GM 4.3 computer in a 5.7 van, it’ll work and the thing will run on six cylinders (since as far as the ECU knows, it’s only got six). I legit did not expect that van to start before the ECU was programmed, but it did.
What’s funny is when the little things are what do you in. Chrysler used multiple patterns on their cam sensors, and if you put the wrong year engine (or wrong reluctors in) it might not start at all, ‘cause it’s seeing a pattern the computer can’t make any sense of.
I think they couldn’t hit emissions with it. Although I’ll give them credit, they kept that engine going longer than anyone else kept an inline 6 gas motor, and it was very dependable. In fact, I skimmed through an article on Facebook about the 3 most reliable engines. All three were inline 6es: the Ford 300 (4.9L), the AMC/Jeep 4.0, and the Chrysler slant six. I would have also included GM’s stovebolt six on that list; I have a 78 Chevy with that engine and can tell you from experience that it will keep on running with no oil in the crankcase, four quarts of oil and ten quarts of gas in the crankcase, on only three cylinders, overheated beyond what the temp gauge can read, and while on fire.
5647457
Sometimes I put them there. Sometimes I forget and don’t.
I can’t remember if I was clear in the blog, but based on experience I was sure that it was an oil pressure problem and that the phasers wouldn’t fix it, but it was covered by an aftermarket warranty and they weren’t going to spring for an engine, so. . . .
Good times! We’ve got a disaster of a Ford that’s going to be that long before it runs, if it ever runs again.
5647483
Pretty much, yeah.
Been a while since I’ve seen something with a hole in the block. Maybe we’ll get another one, those are always fun. Easy to diagnose, too.
5647586
I’ve never gotten a good picture of that (but I’ve tried) . . . sparkly oil is always fun to see.
5647600
What I find impressive is the number of badly-maintained cars I’ve done oil changes on that have glittery oil (or transmission fluid) that amazingly keep running. Heck, one of the guys I used to work with had a Cavalier station wagon with around half a million miles on it and one completely dead cylinder that had been dead for over a hundred thousand miles. He kept driving it because it got great gas mileage and just wouldn’t quit.
5647621
yeah. Cavaliers were great for that. We had a '93 that lasted until 2015. All except the hood which had the practically trademarked rust spot that eventually required the hood to be replaced.
I remember my mom calling me when it broke 1,000,000km and it still lasted another year or 2 before repairs started getting too expensive.
5647603 I've long since learned to never trust a factory worker to do my job.
5647607
SCE to AUX was a backup computer function on one of the Apollo missions during launch. A lightning strick tripped the launch computers power bus, which controlled the stability of the vehicle by gimbaling the main engines, but there was enough time buffer in the system to switch over to the axilary power supply, computer, which ran at 5 volts instead of the main system 30 volts?
Grep is a Linux terminal command for proseeing text, tehres lots of jokes for it because for some reason Linus couldnt bring himsel to add even a 1970s 8 bit GUI to the system. Maybe he hated TRON?
mAh to Farad is what you get when charging up electric cars, specifically Ultra and Hyper capacitors? 1 Amp for one hour is one Amphour, and an Amp is 1 Coloumb of charge fr one second, and a Farad stores One Coloumb of Charge. Electric vehicles can have DVD case size hypercaps of over One Thousand Farad. Which is 1000 Amp seconds, a third of an Amphour, or roughly 350 mAh? which is roughly equal to the very lowest capacity single AAA battery from the dollar store?
5647621
I can remember a few cases where we got tractors in with slow loaders and a transmission full of glitter from a busted hydraulic pump.
That and a few customers trying to economize a bit on oil changes then wonder why their turbos blow. It turns out that while the engine doesn't seem to mind going 800 hour past a 300 hour oil change the turbo does mind quite a bit.
5647635
Most of my cars have failed due to rust rather than mechanical issues. Granted, it was usually a mechanical issue that was the final nail in the coffin, but it was obvious the rust was so severe there was no point in doing any further repairs.
Odds are that’s what’s going to be the end of my current minivan. It’s already going around the bottoms of the doors and the hatch; it’s probably only got a couple years before it’s really sketchy. I could spend a couple thousand on bodywork, but what’s the point?
5647668
I suppose, but where do you draw the line? I mean, surely you get some of your parts already assembled, rather than building everything yourself from scratch. I coulda checked the Suburban engine before I installed it to make sure nobody had dropped anything in the intake (and I do, now). Never had a reman where somebody screwed that up before, though.
5647685
Got it, thanks!
5647704
A lot of cars and trucks have really nasty power steering systems; they’re rarely every cleaned/flushed during the vehicle’s life, and the fluid usually isn’t changed unless it leaks out. Most of them are designed to deal with that, at least in my experience.
We’ve been finding lately that it’s not the lower end of the engine that fails due to lack of oil changes, but other, more sensitive components higher up on the engine. We haven’t seen all that many turbo failures on cars yet, but they’re coming.
5648391 Not exactly a factory worker, but I've had a machine shop miss a spot with the silicone that goes between the head and the camshaft bearing cap plate thingy.
5648394
We are kinda lucky in the tractor world in that the power steering either runs off the main hydraulic system or has it's own pump that draws from the transmission so the fluid normally gets changed fairly frequently. It can still get pretty nasty but they are built to handle it.
They have to be reliable as unlike in cars most tractors have no direct connection between the steering wheel and the front axle.
The turbo failures weren't common but they are pretty much the most delicate thing on those engines.
5648390
I mean... Are you able to do bodywork? If not it's an excuse for more certifications and training.
re the picture with the No. 3 main engine:
...I bet there was an exciting day in that engine room.
...A debris screen that can only be cleared by taking off the cylinder head does not sound to me like the best design, I'll admit. Presumably they had some reason for it?
Thanks for another interesting blog post!
5647483
Reminds me of Chumbucket, from the 2015 Mad Max game.
"Eight is the magic number! You and me, we're gonna land a Big Chief! A bona fide bad boy, 429 cubic inches, 460 horses holy rollin'! Nobody could touch you on the blacktop, day or night! You'd be evergreen, eternal, road-trippin' with the Gods!"
Praise to the Angel, Combustion!
5648407
Finding a good machine shop is hard. Our cylinder head for this thing is at a machine shop now to be hot-tanked. It’s been there over a week, and apparently they haven’t gotten around to putting it in the tank yet. . . .
5648421
I think Mercedes considered a ‘steer by wire’ system for a road car, but as far as I know, that’s not legal in the US. More and more cars are going to electric power steering, which at least leaves customers not having to deal with power steering leaks. Early designs had a manual rack with a drive motor under the dash; more modern designs have it all integrated in one rack and pinion unit, typically with the computer controller built in as well.
Honestly, for as delicate turbos are, it’s surprising that they don’t fail more often. Especially with as well as the average customer takes care of their car or truck.
5648429
In theory? Yeah. But I really don’t want to, and especially not when it’s structural. The cars I daily drive are cheap cars (many of them literally bought on the way to the junkyard), so I don’t have the incentive to spend a lot of hours or money on fixing rust problems.
5648489
From what I remember of the report, it was. On the plus side, the crew did everything right, so it wasn’t a disaster; they isolated the engine room and put out the fire, then used the two engines in the other engine room to sail back to port.
Yeah, they could have had a better design for that. Ideally, if you keep up on maintenance, the screen never gets plugged, and usually when it does get that bad, you’ve got other engine problems on the horizon.
It would be smart if they put ones in that were easily replaceable. Most of the GM and Ford designs I know of either put the screen where it can be easily changed, or they’re part of the cam solenoid.
You’re welcome! Stay tuned for more, I’m gonna post one about that Town and Country with a massive network failure soon.
5650397 lmao you think that's bad? All the machine shops in a 100 mile radius are telling us August is the earliest they can do anything (and that was back in March). And our go-to machinist went on vacation and broke his fucking shoulder, while he had our Nissan Titan v8 block and heads. With a modicum of luck, apparently the block and crank are perfectly in spec (with 250k miles lol), so we're gonna get those back in the next couple days and start putting it together.
Incidentally, he still has my Ford 460 heads for six fucking months now. I mean, I know he knows it's sort of a side project, not a customer's car, but Jesus wept, six months? This is just the state of the industry right now, that's all. We've already had to tell two customers there's nothing we can do. Shame.
5650402
That's good.
Thanks for the information.
"You’re welcome! Stay tuned for more, I’m gonna post one about that Town and Country with a massive network failure soon."
:)
In other more-difficult-than-it-should-be repair news, I'm currently enjoying a mug of hard-won tea. Earlier, my well-used electric kettle failed. A quick check with a multimeter indicated that the failure was fortunately in the base rather than in the kettle proper. Down in the basement, I discovered that the base was, indeed, very simple inside, and the repair of what had failed was pretty simple and easy for the tools we had.
Eventually, I discovered that.
Eventually.
You know what took up most of the time I spent on the repair?
Cutting a big hole through the plastic casing.
Because someone decided that making the three screws holding the cover on something simple like philips head just wouldn't do, oh no; they're some sort of triangular thing that, even with all the drivers and bits we have in the workshop, I didn't find anything to fit. So, to work I go, trying to carefully cut it open. And, of course, the one time I chance drilling a bit of the plastic in a particularly difficult area out, it turns out that right on the other side of that one spot was basically the only place one of the wires (and not even the one that had the original fault on it) touched the case. So then I had to try and fix that, too.
Well, I got it working. One of the wires, which, again, would have been completely fine if they'd used simple screws, has electrical tape substituting for some of its insulation, and there's a gaping hole in the underside of the casing which I'm hoping to cover up next week. Urgh. Good thing it wasn't in the kettle, no way I'd have gotten that safely enough put back together after opening it up, given it uses the same screws.
But. I have tea. Take that, manual, and your claim of no user-serviceable parts!
(But. Seriously, why. Why. Was this supposed to be idiot-proofing? Can't let the average consumer be able to take the casing off, or they might plug the thing in and then lick the exposed contacts? Well, if they're liable to do something like that, they could just stick their screwdrivers in the power outlet and lick them directly, you know! But I suppose that wouldn't have left the kettle manufacturer liable. Sigh. It's a good kettle. Served me well for many years. Hopefully going to last many more.
But still, annoying.)
...Erm. Aaaand sorry about the rant.
...Appropriate place for it, though, hopefully? :D
Anyway, yes. Right to repair? Good thing.
(Ahh. But, I have tea. :))