Hi Guys, I'm the newbie as I just bought my 99 F150 4.6 4x4 about 5 days ago. Coincidently, this problem JUST started 2 days ago. I will not buy any lottery tickets this week. But Mark, this is some great advice. I know for FACT that the oil was changed every 3k for the last 100k or so and this light/dummy gauge has NEVER came on. Now it has. So, with that said, do you feel that the carbon build up could be an issue? I want to test if the pick up screen is clogged, and I was thinking blowing pressurized air into the oil filter intake? Not sure if it would work or not, or if there is a better way. I never heard the engine tick yet, (even letting it run for 15 sec or so with the light on) and I tend to power brake it slightly at red lights and that tends to get rid of the lamp.. I already did the pressure switch and the actual gauges are on order from Summit racing. Should I attempt to douche the engine with the light oil and flush mix first? I'm not really familiar with the truck so I can't really say if it is losing any power or not, but it seems like I have to put my foot in it to get it down the freeway @ 70mph. Your advice would be much greatly apprieciated. If I have to dump a 460 in it I will, my wife may not like it but thats ok, lol. Thanks in advance for the advice!

Sorry, forgot to mention the truck has about 140k on it

My truck does the same thing every now and then but with the fuel gauge

The oils today have additives that eliminate much of the sludge that would accumulate in engines back 40 years ago. Back then, I knew guys that would fill their crank case full of fuel oil and run the engine for about a half an hour and then drain it and refill it with regular oil. They seem to get a lot of crud out of their engine but I am sure it also did some damage and I would not recommend it today. A really good mechanic that I used to work for told me to remove sludge you should do an oil change and put in good high quality oil. Then drive around and change the oil after one week. This sure sounds a lot safer than using fuel oil but I don't know if anyone has ever tested this by tearing down an engine to see how well it works. You could also add a engine flush products to your oil that are made by folks like BG at the link below.

http://www.bgprod.com/products/products.html

If I had the problem of sludge, it think I would try the one week oil change and add a engine flush product. Then I would try another one week oil change as see if it resulted in even more gunk being drained after driving around for a week. It would be inexpensive and low risk to experiment with this approach and a lot easier than tearing apart the engine

If this is a sludge/carbon issue, I may try to go a little aggressive at first and try the flush first. I don't want to do anymore damage to it by continuing to drive it. I'm still slightly power braking it (about 1k rpm) and that seems to be doing the trick on the light, I just don't know what kind of pressure I'm getting driving it down the freeway, I am being gentle with it though. I'm going to look into a flush tonight so thanx for the link, any other advice from anyone would be helpful too. I don't really want to slam a block in a truck that I've only owned a week.. Lucky me! Lol

A motor oil TV commercial many years ago showed how good motor oil cleaned by having a mechanic with very dirty hands pour fresh motor oil on his hands and rub them around to clean them. His hands were as clean as if he used a hand cleaner. I tried it myself and it works but I wouldn't do it today because the chemicals cause cancer.

Good thought, thank you!

What engine do you have? How many miles on it?

If you just have standard gunk from not changing oil often enough, then that may work. If you have clean oil and no sign of coolant on the dip stick, then it maybe worse than you think. The 4.2 '97-'03 V6 has a problem with the intake manifold leaking coolant into the oil. It mixes and turns the oil onto the worst sludge I have seen! It can't be flushed out, it has to be brushed out with solvent.

Unfortunately the 2WD F150 of those years has the cross member right under the pan, so you have to raise the motor, pull the pan and pick-up tube. This gunk was so bad I couldn't get it out of the screen, even with brake cleaner. Replace the whole tube!

As for fixing the manifold leak, you have to pull it and replace the gaskets! Now here is where the problem started. The gaskets are 1/8" plastic with a small rubber washer fixed to the plastic. Best I can figure is the rubber washer that seals the intake ports and coolant holes are too thin to seal tight. With the thick, hard plastic gasket, you can't torque it any more. I added a layer of silicone on both sides and it seals! It's a bitch to mess with, but removing the upper and lower manifolds is not that hard.

To remove the pan, remove the drive shaft and rear tranny mount. Unbolt the motor from the mounts and raise the engine about 6-12". Without the manifolds on it will clear the firewall just enough to snake the pan off and replace the pick-up tube.

Don't waste your time on different oils or coolant, it still coagulates and clogs the screen.

I know this sounds terrible, but it is what it is! I had to do mine twice! Replacing the gaskets alone, will NOT fix the problem. The second time mine did that, I pulled the motor and rebuilt it. It was very clear that this is the problem during the rebuild!!!

Mine had 160k miles when it clogged the first time! If you have seen the original post I put in, there are pix of the tear-down and the infamous gunk from hell!

Not that I know of!
 

Unless you have a 4x4, there is nothing that I know of! Wish someone would find a solvent that would clean the gunk and not damage rubber parts etc.

Good luck!