1993 F150 4x4 XLT 5.8L 136k miles, original owner, all stock, motor has never been touched.

I am experiencing what appears to be reduced oil pressure, as displayed on the idiot gauge in the instrument cluster.

As long as I've had the truck the gauge needle aligned with one of the legs of the M in the word NORMAL printed on the gauge face. I've recently noticed that the needle is now centered on the O. I've had vision problems for years, and only recently had full sight restored in one eye, so I don't know how long this has been going on.

I've noticed a clicking or tapping sound, apparently coming from the front passenger side area of the engine compartment which, after reading here, I'm hoping is related to the cam phaser, but it may be valve related. I'll be looking into that issue next.

The truck uses no oil, and generally runs great.

I purchased a gunk out product, hoping to clean out the oil passages to improve the pressure, but after reading here I returned it, fearing that the release of more sludge may clog what may be a partially clogged oil pickup tube.

I have always used Fram filters...DOH!...and after reading here, today I changed the oil and filter to Motorcraft. I plan on watching the gauge to see if it helps. I saw no metal in the changed oil, and I saved the filter to cut open to see what might be trapped inside. I don't know if I have the courage to raise the motor and drop the pan, and don't want to pay for it.

As always, any suggestions would be greatly appreciated.

 

A 351 doesn't have cam phasers.

 

What has been your oil changing habits been over the last 21 years??

Do you change the oil when it's hot or cold?

My first guess is that the oil pump screen is probably getting clogged up with sludge..

Or, it could just be the oil pump itself, but that's not as likely IMO..

What weight oil are you running?

If you've been running Fram filters for the past 21 years, you probably have some wear due to dry starts, and that could be the loss of pressure too because of the increased clearances on the bearings and such??

Or, it could be the oil pressure sender itself?

I think your best bet is finding out what's in the pan, as that's the most likely thing that's causing your low pressure..

Good luck!

Mitch

 

Uhh oh, that doesn't sound good. Must be the valves. I'm planning a big fishing/diving trip to Canada in 30 days, and was hoping it would make it.

MitchF150: I'm embarassed to describe my maintenance habits here. She largely sits, but being the F150 that she is, she just keeps running. I change the oil about every 7-10k, but that ends up being about every 1-2 years. (Now hanging head in utter shame and humiliation)

I would say I generally change the oil when it's warm, cuz I'm a wus.

I have typically used some form of 10w30 oil. Some inconsistent recognizable brand name available from Costco. I never placed much stock in the various oil claims...and figured all the brands were probably acceptable. Opps.

As long as I can remember I've been running Fram filters, since it was a popular name I recognized and never found anything visible in the pan. I suspect I may now...grrrr.

I am an Aeronautical/Astronautical Engineer and Inventor by trade...but I don't feel like a rocket scientist posting this.

Sounds like I'd better try to locate a shop for at least a valve job and pan removal.

Thanks guys.

 

Don't feel too bad.. For a rig that does not get driven daily, that's to be expected... My wifes car is mostly driven locally and sees the hwy about once a week, but I just changed the oil in it last weekend after over a year, but it only had 5000 miles on it since the last change..

No sign of sludge in it's oil, as I drive it around for about 10 minutes before I change it, so yes, it's a bit hot, but that's what gloves are for..

My best guess is you have sludge on the pump screen.. Dropping the pan and cleaning it up will most likely solve your problem..

10w30 sounds like the right oil for that era of engine, and oil brand preference is mostly a personal choice and as long as the oil meets the specs for your engine, you are generally going to be fine.. Just for conversation sake, I use Castrol "Edge" oil in the wifes car and my old 97 F150 that had over 255,000 miles on it before I traded it for the 13..

I'm gonna check out the Motorcraft semi syn oil for the 13, as that's what's in it now from the dealer and it's under that warranty thing for the next 3 years...

Good luck!

Mitch

 

The lack of cam phasers now has me focusing on the rattling noise.

I looked on ebay, and listened to a dropped valve, and my noise is not yet that bad.

Would a dropped valve generate any type of OBD code?

I see that relatively minor valve issues, such as problems with the springs and lifter componenets might be repaired without a head job.

Does this sound like a reasonable plan: test the compression to see if the valves are seating properly. If not, pull the valve covers and survey for any problems.

When using a compression tester, do I actually start the motor, or try to crank it manually by hand?

If the noise is not related to the valves, is the timing chain the most likely cause?

Thanks.

 

To do a compression test, remove the spark plugs, pull the coil wire and fuel pump fuse. Have an assistant hold the throttle wide open and crank the engine with the key.

 

What does holding the throttle wide open do? Seems redundant if the fuel pump fuse is pulled.

Also, is it necessary to pull all of the plugs if I only want to check one or two cylinders?

Thanks.

 

To do it right, a compression test is run with wide open throttle for no air restriction. You need to check all 8 to check for consistency, again to do it RIGHT.

 

Before you do a bunch of work, have some one or you can do it, put a mechanical oil pressure gauge on it. The reading of the "gauge" on the dash is meaningless. It either reads pressure or it doesn't, kinda like an idiot light that's either on or off. It does not directly read oil pressure. As these units get old they will drop in the expessed values they show. In regards to the rattle, is this something new or did you just now notice it? These engines from this era were put together extremely loose and they make clattering noises. My 91 Bronco sounded like a thrashing machine when I got it and it still rattles and clatters 135,000 miles later. You can quiet one down with heavier oil but it's not really hurting anything. I would suggest that you change the oil using a high detergent oil like Rotella or any of the dual rated oils and change every 2000 miles. I'd give it that regimen for the next 4 oil changes. The idea is to clean up whatever has accumulated over the years and let the oil filter catch the junk as the detergents do their job. If you don't have many below 32F startups, you can use the Rotella 15w-40 in that engine. It has large enough drain ports to handle the slightly heavier oils. I've had 15w-50 in mine with zero issues except fuel mileage. You will, however, need to drive the unit more for the detergents to work.

 

GLC:
I agree that doing it right is worth the effort, and my questions on something as simple as a compression check may be interpreted as sloth, but I ask becasue I want to make sure I am doing it correctly. In case you couldn't tell, I don't have much maintenance experience My take on the compression test is that, in this instance, my goal is just to see that I have some reasonable compression value, to eliminate the possiblity that the noise is a failed valve. I saw a YouTube video on how to do the test, and it mentioned to remove all of the plugs, so I was asking if this is actually part of a standard check, and why all of the plugs should come out.

Labnerd:
Rojer on the oil gauge. I'm already shopping for an aftermarket unit to install. After seeing several warnings of unleashing sludge with efforts to clean, I changed the oil to motorcraft 5w20, and stocked enough with filters for 3 more changes in close succession. I'll get a guage installed, watch the oil when I change it, and if the pressure is in fact low, I plan to pull the pan and clean the pump screen. Prior to the pan pull I'll try to clean the gunk with a detergent cleaner of some sort. I saved my old oil filter to cut it apart and see what it has caught.

If I dissapear for a bit, its because I'm out getting dirty.

Thanks to all for your invaluable help.

 

I've looked in the fuse guide and the chilton's manual, and find no fuel pump fuse.

I've got the plugs out, but don't want to crank it for the compression tests without some guidane on the fuel pump fuse.

The good news is all 8 plugs look great, so at this point I think the valves are working. I decided to just replace the plugs and plug-wires, rather than wait for a response to the question as to wether or not I had to pull all of them.

The question now is how to disable the fuel pump for the compression test.

EDIT: I found in the chilton's book that the fuel system power is fed by a fuseable link near the starter...I'm still looking for that. I was thinking I might disable the fuel by triggering the inertia switch. This kept the truck from running before, until a helpful member here accurately diagnosed the problem for me.

EDIT: NEVERMIND: I pulled the fuel relay

Thanks.

 

Compression test results:
CYL COMP
1 140
2 135
3 140
4 130

5 130
6 140
7 145
8 145

Engine mileage is 136k. This test was done dry.

After I did the test, I learned that I should have warmed up the motor first...doh!

I don't have a buddy to help, so the reported values may be 5psi below actual due to minor leakage as I stumbled around to the front of the truck after cranking.

These results seem to indicate that my valves are working ok.

I also learned that I have another whole fuse/relay box in the engine compartment that I didn't even know about...woo hoo.

I'll try to load a sound clip of the engine running. With that, perhaps a more experienced ear can tell me if the rattling noise I hear is the timing chain, or if I'm lucky it's not a problem at all. I'm not sure when the chain is supposed to be replaced, but mine never has been.

Thanks.

 

Those are good compression numbers.

Have you pulled the valve covers to see how much sludge you really have?

 

You went the wrong direction on the oil. The 5w-20 is going have that old engine really sounding like a thrashing machine- it's too thin for it especially with the miles on the clock. I wouldn't run it long like that. The issue is the oil running out of the now worn lower bearings. These bearings also provide the oil spray to the bottom of the pistons for lubrication. If the bearings are worn, and they are, there will be little to no oil make it to the rings. Wear will be great. You need to go up on viscosity, not down. I would strongly suggest the dual rated, high detergent oils like Rotella, Delo 400, DelVac in a 15w-40. The thicker oil means less runs out of the worn bearings and more gets to the ring packs.
If you are judging the noise from the engine with the 5w-20 oil, it's probably attempting to disassemble itself from the thin oil. I wouldn't run long like that if at all.