First time poster here...

I just purchased a 1986 F-150 2WD 302, with 85,000 original miles. During my drive home from picking it up, I noticed a strange noise coming from what sounded like the right bank of the engine. Keep in mind that I believe the orginal owner used this as a farm truck, which means it probably never spent any time on the interstate.

When I first start up the truck, it runs great -- no missing, no rough idle, etc. During the test drive around town, the engine ran great. But, after driving about 10 minutes on the expressway, the engine started ticking. It sounds similar to an exhaust manifold leak in one cylinder at cruise, but during idle it sounds like a diesel engine idle (auto ignition).

After I first heard the noise, I pulled off the highway to inspect. As I was coasting, the oil pressure dropped to the lowest point in the "normal" range. I turned off the engine and pulled the dipstick. The oil level was fine, but the dipstick seemed really hot. Thsi may not really indicate anything, since the dipstick tube runs very close to the left bak exhaust manifold.

The whole time driving, the coolant temp was near perfect (according to the factory gage). The odd thing is that the ticking noise would go away sometimes, like after turning the engine off for a few minutes. Even while cruising around 50 mph, the noise would come and go.

To me, it seems like this issue is being caused by heat buildup in the cylinder head, since it isn't a constant sound level. (Mechanical problems like main/rod bearings should have a pounding/thunking noise that stays at a consistent loudness after the oil heats up.) A Mustang friend of mine thinks that it could be heat buildup from the exhaust system (old clogged cats).

Any thoughts?

 

it could be the exhaust manifold(s) are cracked and are only leaking when they get real good and warm.

First thing i would do is: ditch the factory gauges and get some mechanical ones. The factory gauges aren't very accurate IMHO (better than nothing though).

 

Sorry, this statement "Mechanical problems like main/rod bearings should have a pounding/thunking noise that stays at a consistent loudness after the oil heats up.) " is not true... and there is a tech bulletin out for these engines which says there is a possiblity that the first four main bearings were sent out of the factory with too much clearance... ( but not the number five )... and that the noise is at certain types of load/rpms.... but I think your ticking might be a hydraulic valve lifter going bad..... notice I have the same truck...LOL

 

The good news is it can be corrected with the engine in the truck... my front and rear seals and those in the trans are leaking.. bad news is our engine has a single rear crank gasket which requires the trans to be dropped to replace... I am going to do/check everything at once.. and on old cars I automatically put a new oil pump in when I have the pan off... and I get great longivity out of my engines... also.. on old engines I change to straight 40 wt oil...this will also help on increases bearing clearances..

 

I understand about the main bearing tech issue. Is there some place where I can find more information (like a dealership TSB/Notice) about this particular problem?

The ticking noise that I had on my engine seemed like a preignition problem since the engine sounded like it was dieseling at idle. I'll continue with the addition of fuel injector cleaner in the next two tanks of gas in the hopes of cleaning out any deposits in the intake/combustion chamber. (Recall I mentioned that this truck has 85,000 original miles, probably subject to farm-only use -- meaning light loads and low speeds.)

 

An update on the problem and a question to get some feedback:

The update -- What I have found over the past couple of months is that I had an oil pressure problem. I first installed a mechanical oil pressure gauge to conform the problem. With 20W-50 oil, the gauge would read 50 psi cold and 10psi hot idle/20 psi hot running. In addition, if I ran the engine speed up past 3000, the oil pressure would drop to zero.

So, I decide that I would install a high-volume Mellings oil pump, assuming that the main bearings were a little oversized. As you probably know, to drop the pan to get the oil pump out, you have to remove the upper intake. I figured since it was down that far, I would replace the valve cover gaskets (leaking) and install a new thermostat. Then, I might as well put in a new water pump for cheap insurance, and replace the lower intake gaskets (the front cork gasket was completely blown out of place.)

What I found was disturbing -- when I removed the valve cover gaskets I found a LOT of sludge -- about 1/8-1/4" thick over all the head surfaces. I also found the root cause of the pressure drooping to zero after 3000+ RPM -- the oil drainbacks in the head were completely plugged. All the oil was in the top of the engine at higher speeds.

So... About 12 cans of degreaser later, the heads are clean and the oil drainbacks in the heads and lifter valley are open to allow oil flow. While I was at it, I hosed out the oil pan and pickup tube. When I reinstalled everything, I Primed the oil pump for a good 15 minutes to get the oil circulating around and any residual gunk flushed out. (Note I did not completely removed the oil pan since the exhuats would have had to come out, and I didn't want to risk breaking the bolts to the manifold in the process.)


Now for the question -- I have great oil pressure all all times -- about 60 psi cold and 35 psi hot idle and 45 psi hot drive. But, there occasionally comes a time where the oil pressure will drop to 25 psi and DECREASE with engine speed. During these times, I hear a buzzing noise coming from the engine that sounds similar to a loose heat shield (resonating sheet metal). I'm lost here. I changed the oil once and the filter twice since the ordeal, and I don't know what's causing the pressure drop.

Any advice???