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Discussion Starter #1 (Edited)
Hi there.

I combed the threads looking for help but it seems every other "oil pressure" issue was caused by either a bad sending unit or a bad gauge: unfortunately, this is not my case. Pressure actually drops.

I own a 94, 4.6 Tbird, I bought it at 150k miles and has had no major issues, other than small routine maintenance tasks.

Car ocassionally had this oil pressure issue when it was an automatic, but I just finished the 5 speed swap a few days ago and now it's a lot worse, can't drive it untill I fix this.

I know for sure it's neither the sending unit or the gauge because the lifters start tapping some seconds after the gauge drops and the "check gauges" light comes on.

What baffles me the most is that every time it happens there's no way to link it to a particular condition or operation status. It started happening a few months ago, when I revved the engine a couple times above 3800 or so, in neutral, ever since that time, the problem shows up randomly.

First thing I did was changing the oil and filter (thinking filter was probably too dirty and restricting flow). No luck, issue continued so I disassembled the front cover and visually inspected the pump: No signs of wear whatsoever, steel surfaces still had the original machining patterns, the thing looked spotless. I checked the bypass valve and it seemed fine too. That time I also made sure the retun bores from the heads to the oil pan were trouble-free (thinkig the heads could be keeping most of the oil on top, and not draining it fast enough as I initially thought this was a high-rpm related problem, which I later ruled out).

As I said above, the fact that this is a completely random malfunction confuses me a lot. Last night it started while I was doing the first driving tests around my neighborhood with the 5 speed. I parked the car as soon as I heard the valve lifters, waited a few minutes, started the car again and drove some blocks back home, the problem came back a couple more times along the way back, but it seemed like giving it a little more throttle increased the pressure so the "check gauges" light went off, but as soon as I lifted my foot off the pedal, the pressure dropped again... later on the way back, pressure stayed good without giving it gas, so I was hoping problem was over, maybe some air in the system, aliens, I dont know!! :smile2::crying:

I got home and left the car idling, a couple minutes later, the lifters started tapping again, turned it off and waited. Started it and pressure was restored good for some 5 minutes and then it dropped, lifters making noise again. I tapped the throttle slightly, trying to link the problem to a specific range of RPM's with no luck, this time, giving it light throtle made no difference, or very little, the lifter-tapping was not bad, but I could still hear it.

Car is a bit above 200k miles now... Oil is new. I put 15-W40 last night and used a new Bosch filter (which I'd say is good quality)

What's your guess?

The only diagnostic I can venture now is:

The pump bypass valve is getting stuck in the open position (erratically) because oil pressure is building up too much (oil passages and galleries too obstructed). When I bought the car, it had 150k miles AND it had a slight oil leak (that I didn't know at the time it was located in the oil filter base gasket) ... I was stupid enough :frown2: to put high-mileage, thick oil in the engine AND an anti oil leak additive on top of that... I guess this combo plus some neglect from the previous owner caused oil crud in the engine.

I will hook up a real oil pressure gauge and find out if I'm on the right track tonight.

Any ideas?

Thanks!
 

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Most likely your lifter tick and gauge issues are semi-independent problems, semi being the root cause may be the same: You’re running way too thick of oil, and the stopleak probably made it much worse. The lash adjusters get noisy with thick oil because the tolerances are tight in them, same with bearings, you can actually increase wear in an engine film from running heavy weights since it’s too thick to form a film in tight clearances, and the leak additive likely gummed them up and seized a few as well, possibly even your sending unit.

The sending unit is an on/off switch, not a real pressure sender. 6-7PSI and above will point the needle on the gauge straight up constantly with the engine running and any fluctuation you see is more indicative of wiring connections and charging system integrity than it is oil pressure, unless it’s dangerously low. Generally speaking, even an engine with severe wear with no oil pressure at idle will still build pressure at 3800rpm where you see it drop, so that wouldn’t worry me.

I’d dump the oil for 5w30 and run a half-full quart of seafoam or ATF through it for a few miles to try cleaning it out and change it again. I’d get a real sending unit for the gauge and jump the resistor for it behind the cluster(it fixes the needle position) and worse comes to worse change out all of the lash adjusters if they’re still noisy.
 

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Discussion Starter #3 (Edited)
Most likely your lifter tick and gauge issues are semi-independent problems, semi being the root cause may be the same: You’re running way too thick of oil, and the stopleak probably made it much worse.
You think 15w40 is still too heavy with an engine this old? ... If so, these things are ethernal!!!


The lash adjusters get noisy with thick oil because the tolerances are tight in them
The noise I hear when the engine is idling is definitely more characteristic of valve clatter than timing chains being a little loose... I think it's only the lifters making the noise.

I’d dump the oil for 5w30 and run a half-full quart of seafoam or ATF through it for a few miles to try cleaning it out and change it again. I’d get a real sending unit for the gauge and jump the resistor for it behind the cluster(it fixes the needle position) and worse comes to worse change out all of the lash adjusters if they’re still noisy.
Wouldn't you worry about the Seafoam freeing up carbon deposits too much? ... I mean, wouldn't that be somehow the same as switching from regular to synthetic oil? ... I've read horror stories about guys whose engines didn't smoke but started doing it after the switch to synthetic because the carbon build up was actually sealing stuff like valve guides. (And another thing is I haven't seen Seafoam in Mexico, even in stores such as AutoZone and Napa, which carry lots of imported stuff)

I found this on youtube: The issue sounds and looks exactly like mine, same erratic behavior of the gauge, minus the constant clatter sound, which is on and off, hope it's nothing like he describes on the comments.

 

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Definitely need to hook up a real gauge. In case you didn't know, the "gauge" you see is just an idiot light made to look like a gauge. If you have more than 7psi of oil pressure, the gauge goes to somewhere in the middle. If you have less than 7, it goes to zero. Also, 15W40 oil is way too thick! 5W30 is more appropriate, but since your issue seems to present once it is warmed up, and not cold, I don't think that is your issue, but once you get the issue resolved, switch back to a lighter weight oil. The Bosch filter is a good quality piece, so I doubt that is your problem. At this point, I would probably be looking to maybe a clogged screen on the oil pickup tube. Unfortunately, to drop the pan and see that, either the engine has to come out or the front subframe has to come down.
 

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You think 15w40 is still too heavy with an engine this old? ... If so, these things are ethernal!!!
Age and mileage makes no difference in oil weight, that’s something you can do as a last resort bandaid if you wipe out the main and rod bearings so the thicker oil film takes up the extra clearances from the worn bearings, but on an otherwise healthy engine you should stick with the factory recommended weight.


The noise I hear when the engine is idling is definitely more characteristic of valve clatter than timing chains being a little loose... I think it's only the lifters making the noise.
Lash adjusters = lifters. They don’t “lift” pushrods, but they serve the same purpose.

Wouldn't you worry about the Seafoam freeing up carbon deposits too much? ... I mean, wouldn't that be somehow the same as switching from regular to synthetic oil? ... I've read horror stories about guys whose engines didn't smoke but started doing it after the switch to synthetic because the carbon build up was actually sealing stuff like valve guides. (And another thing is I haven't seen Seafoam in Mexico, even in stores such as AutoZone and Napa, which carry lots of imported stuff)
No. If it’s going to burn oil it’s going to burn oil, the problem like with oil weight is the double edged sword, carbon deposits gum up critical parts, like lash adjusters and piston rings. I prefer using ATF for this purpose myself, you’re not filling the crankcase with the stuff, just a half-full quart and just for a couple miles.
 

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Discussion Starter #6 (Edited)
Definitely need to hook up a real gauge. In case you didn't know, the "gauge" you see is just an idiot light made to look like a gauge. If you have more than 7psi of oil pressure, the gauge goes to somewhere in the middle. If you have less than 7, it goes to zero. Also, 15W40 oil is way too thick! 5W30 is more appropriate, but since your issue seems to present once it is warmed up, and not cold, I don't think that is your issue, but once you get the issue resolved, switch back to a lighter weight oil. The Bosch filter is a good quality piece, so I doubt that is your problem. At this point, I would probably be looking to maybe a clogged screen on the oil pickup tube. Unfortunately, to drop the pan and see that, either the engine has to come out or the front subframe has to come down.
I was afraid things were heading this way... I was aware of the gauge being just a on/off thing made to look like a gauge... I'm going to bypass the resistor in the cluster and get the right sender... Although that'll be just later for me to see the actual oil pressure but I'm pretty positive now it's not a gauge or sender issue because of the lifter clatter which happens a few seconds after the gauge reads zero...

Back when I took the front cover off to check the oil pump, I used a funnel and ran about a full gallon of gasoline down the pick up tube (trough the upper end that's bolted to the pump) ... ... I was kind of expecting the fuel to not flow freely -if the screen was actually clogged- or to free up whatever was stuck down there but the tube guzzled tha gas freely. I collected the gasoline through the drain and did this twice... I also poured gas directly into the pan and found no debris or chunks of whatever... the plastic tensioners were not broken either so I wouldn't worry about plastic clogging the screen... After running the gasoline through the tube, I used compressed air to blow anything loose down the pick up screen... nothing came out the other end.

I'm out of ideas other than blaming the pick up tube (cracked and sucking air in), clogged screen, or shot oil pump.

Worst case scenario: maybe the the oil passages and galleries are all gummed up and clogged, so pressure builds up and the bypass valve opens and gives me zero pressure, but ... as I explain this, I find myself disbelieving it as this would create a cycle: Valve opens, pressure drops then valve closes so pressure increases again.... and so on... (unless there's a possibility that the bypass valve is worn or faulty and gets temporarily stuck in the open position... )
 

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Discussion Starter #7
Age and mileage makes no difference in oil weight, that’s something you can do as a last resort bandaid if you wipe out the main and rod bearings so the thicker oil film takes up the extra clearances from the worn bearings, but on an otherwise healthy engine you should stick with the factory recommended weight.




Lash adjusters = lifters. They don’t “lift” pushrods, but they serve the same purpose.



No. If it’s going to burn oil it’s going to burn oil, the problem like with oil weight is the double edged sword, carbon deposits gum up critical parts, like lash adjusters and piston rings. I prefer using ATF for this purpose myself, you’re not filling the crankcase with the stuff, just a half-full quart and just for a couple miles.

Sorry, I thought the "lash adjusters" were the plastic tensioners or the hidraulic "whatevers" that keep the chains tight.

I'll try the Seafoam tonight (hope I can find it) as a first resource, and report back...
 

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Does the noise come from only one side?

I seem to remember someone having a cam cap come loose; that'll drop oil pressure.
 

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Discussion Starter #9 (Edited)
Does the noise come from only one side?

I seem to remember someone having a cam cap come loose; that'll drop oil pressure.
I'll get an engine stethoscope and find out tonight, I may find something like you mention...

Last night I ran the engine with a 5-minute engine flush... I know I'm taking big chances here: Either it gets better or it'll get way worse!... :crying:

Last night, the oil pressure was fine for the first minutes of the ride around the block while the engine flush did its job... but once the engine reached normal operating temperature, pressure dropped again just like it did three days ago and the valve clattering started. Initial pressure loss was solved by revving engine slightly, but after a minute or so the clatter came back and, in the end, no revving would fix it anymore. Turned the car off, waited 2 or 3 minutes, started it again, pressure came back and filled the lash adjusters and engine quieted down for another couple minutes but then started the same dance again. I turned it off and forgot about it. Wen to to bed... Too frustrating cause besides that, despite having made sure the flywheel seemed like a 0 balance one, I guess it wasn't cause the engine is developing a vibration... :xpcry:

Guess my car won't be ready any soon now... :frown2:

I'm not giving up on this... I'm just a bit tired and frustrated as I have devoted some 10 sundays to this conversion and I was already savoring the success of bolting an M5R2 to this 4.6... and now this! ... My guess with the vibration is that the flywheel only "looked" like a 0 balance unit (no crevice on the iron that gave it away as an imbalanced unit) ... but it wasn't or maybe the clutch assembly is imbalanced (it wasn't a new one) ... guess I'll have to find out about that too.
 

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A flywheel imbalance isn’t going to gradually develop a vibration, if it was smooth before something else is going wrong, did you use threadlocker on the clutch pressure plate and flywheel bolts?

Are you certain the the clatter is coming from the valvetrain? This sounds more and more like the symptoms of spun rod bearings to me.
 

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Discussion Starter #11 (Edited)
A flywheel imbalance isn’t going to gradually develop a vibration, if it was smooth before something else is going wrong, did you use threadlocker on the clutch pressure plate and flywheel bolts?

Are you certain the the clatter is coming from the valvetrain? This sounds more and more like the symptoms of spun rod bearings to me.
I didn't notice it on the first day during the test drive... I noticed it around 2800 rpms when I was back home, revving the car slightly with the 5 speed in neutral as I was trying to determine if the pressure loss was linked with the rpms.

Last night, still in neutral, the vibration was noticeable in a little wider range of rpms, not very strong, but certainly something I was able to pick up instantly ... ... a spun bearing would definitely explain pressure loss, the noise and the vibration too... but wouldn't it produce a CONSTANT noise (I don't know)... rather than an "on and off" noise like the one I have. Once the clatter won't stop for a minute, I'll switch it off, wait some minutes, start it again and once pressure shows ok on the gauge, the valve train starts to quiet down... (or am I looking at both pump failure AND spun bearing... I guess I'll start laughing it off, rather than crying at this point)

Yes, I used thread lock, the red one.
 

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Instead of installing a resistor, just get an inexpensive electric oil pressure gauge and sending unit (I have an Equuis unit in mine) that will feed the low oil pressure light as well as it's own gauge. install the gauge somewhere visible and see what the actual oil pressure is. see if it's dropping.

Second, don't put thick oil in a 4.6 modular. These are 300,000 mile engines and don't need oil so thick. I have a 180,000 mile unit going in my car that you can still see the cross hatching on the bores, and the OEM crank bearings look brand new, and spec out properly.

Thick oil in an "old" motor is something that our grandparents did because they didn't want to fix the actual issue. Same with the bars leak crap. Too late now, but file it under things you learned. You can't "fix" anything with something out of a can, only mask the issue.

Also, revving an engine with no load is bad juju as well.

Oil flushes aren't needed. Drain 1/2 quart, replace with plain old atf, run till warm (after installing your oil pressure gauge so you can see what actual pressure is) and drain, refill with 5w30 of your choice.

See what your actual pressure is, locate the noise. A rod knock is pretty obvious. I found out the hard way when I spun some main bearings due to rapid loss of oil pressure from a rubbed line on my remote mount filter.
 

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Rod bearing noise tends to be noisiest at operating temperature and is somewhat more pronounced at varying RPM ranges. Lash adjuster noise tends to be worse with a cold engine and goes away with running. If you hear noise listening from under the car it's bottom end.
 

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Discussion Starter #14
Duly noted... will report later on.

Only time I get to do something to this car is when I'm back from work, early nights and Sundays.
 

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Discussion Starter #15 (Edited)
Started the car again just half an hour ago, pressure was steady around the neighborhood for more than 20 minutes... No strange noises, no weird stuff except for the slight vibration (which I am now sure is not a spun bearing but something I did to the flywheel to accommodate my Frankenstein super hacked up together set up... (I can't confess it here, if you must freakin' know, let me know and you might convince me enough to embarrass myself in front of everybody... I just had to make this thing work... well... kind of... :grin2: lol)

Now, back to the pressure issue gentlemen: I spoke to a mechanic friend of mine about these issues and he said he was absolutely sure (his words) that the metal screen in the pick up tube's lower end was obstructed with carbon deposit little chunks (remember I told you about the crud I found on the front cover and the heads?... he said he's sure the stuff has come off from engine surfaces and has ended up in the bottom of the pan) and that when I go above a certain amount of RPM's, the suction is such, that it "lifts" stuff from the bottom of the pan an clogs whatever pores are still free. He said that would explain why pressure comes back after I turn the engine off, let it sit a couple minutes and restart.

Well... After driving the car for some 20 minutes with no oil pressure drop or noises, I parked it and took the engine to a little below 3000 rpms for some seconds and then it happened again: pressure dropped to none in the blink of an eye and valves started their clattering business within 15-20 seconds.

My friend's explanation would be consistent with this behavior, the only thing that doesn't make any sense (to me) is that when I took the front cover off to check the pump and poured a full gallon of gas BOTH through the oil pick up tube and in the oil pan TWICE, I found NOTHING in the recovered gasoline that came out of the drain hole that made me believe that there were chunks of oil crud floating around in the pan...

His advice was to drop the pan and clean the heck out of everything under there.

What do you think?

If you agree, what's easier? Dropping the suspension or lifting the engine to take the pan out?

Thanks guys.
 

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If you have access to a lift, dropping the subframe is definitely easier. It is still doable on the ground, but it is much more of a pain. Also, if you have a vibration due to some imbalance in the flywheel, that will need to be addressed before it tears the motor apart, and so if you have to access the flywheel anyway, pulling the engine is probably easier and quicker than dropping the subframe and pulling the trans.
 

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Discussion Starter #17
If you have access to a lift, dropping the subframe is definitely easier. It is still doable on the ground, but it is much more of a pain. Also, if you have a vibration due to some imbalance in the flywheel, that will need to be addressed before it tears the motor apart, and so if you have to access the flywheel anyway, pulling the engine is probably easier and quicker than dropping the subframe and pulling the trans.
Yep... I will duly address the vibration first by changing the whole clutch and flywheel assembly, it's not that bad, but it isn't something I can just overlook, it'd be very stupid... engine was absolutely vibration-free before conversion ... :crying:
 

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Discussion Starter #18 (Edited)
Well, It took me four months to gather the time, energy and determination to tackle the task of removing the subframe to gain access to the oil pan. The pick up tube screen was clogged and the pan was filthy as you wouldn't believe, but it's clean now and no more oil pressure issues... :znanner::headbang:

There are some pictures of the nasty stuff I found in the pan, you'll enjoy'em for sure.

There's a very good tip on using four long bolts to get the subframe "hanging" from them (rather that letting the monster go all the way down and fighting it to bolt it back on while balancing it and adjusting it on the jack all along. There's a WAY EASIER way to do it.

Somewhere in these forums I read that tip from another member (or probably Sccoa's, I don't remember, sorry) It's definitely the most valuable 4 dollars you'll ever spend on these four long bolts.

Read about it here if removing the pan is coming up on your "to do" list:


Whole Thread
https://forums.tccoa.com/44-suspension/188927-subframe-removal-remove-oil-pan.html

Specific post on subframe removal
https://forums.tccoa.com/2046283-post14.html

Cheers everyone.
 
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