First off roading - now some engine problems

[toyotaspeed90]

Well... I did some offroading near my house to put it through some tough situations before we go camping far off & break down for unforseen issues.

So the following happened:
bent the front bumper
ripped the front license plate off
exhaust leak has gotten much worse

Concerning issues:
Oil pressure showing nothing
Valvetrain noise that was there is now

first:
Oil pressure - this didn't happen when over-revving or pushing hard. In fact it was perfectly fine through all the hard stuff and as we were descending on a gentle slope (almost flat) the pressure dropped. No oil leaking, level not low, no engine noise - just dropped. So we stopped, I poked around... and couldn't find any issues. Started it back up and oil pressure was back. (I should also state that there are some electrical gremlins in the truck - for instance the front blower motor won't always come on... and requires me to wiggle/hit the relay box... and it isn't a faulty relay). However about 100 yards down the way the gauge started to quickly move between middle & no pressure for about 5 seconds and then just dropped to nothing.
I wrote this off as being another electrical gremlin... I plan to get a T and at least temporarily throw a true pressure gauge on the engine to see what pressure actually looks like.

second:
Valve clatter - there was always some. After the oil pressure incident I'm not sure if they're related or not. It definitely doesn't sound like a rod bearing (trust me, I've spun enough of those in the past). I got to another difficult spot and it required that I really push the truck hard (and in fact I ended up having to be pulled out). After that the clatter was MUCH more noticeable - especially inside the truck.

Been reading and it sounds like there are common problems with the pushrods & rocker arms wearing along with the hydraulic lifters collapsing on the OHV 4.0 motors (and of course the "fine" engineering requiring the heads to be pulled to replace the lifters :thumbdwn.


I'm also thinking there could possibly be an oil pump issue causing a lack of pressure to build - and as such the lifters aren't pressurizing appropriately & causing noise. There doesn't really seem to be a lack of power in the truck... but the noise isn't just a slight valvetrain noise to be ignored.

I'll try to remember to post a photo of the suspension flexed out & one of the wheels about 2 feet off the ground and the truck as a whole in a rut almost as tall as the truck itself (getting out was interesting).


**edit**
forgot to mention - this is a 1995 4x4 control trac, 4.0 OHV with about 190,000 miles.

 

[deweyville65]

As Tom McCahill would have said, sounds like you need a tank, not an Explorer

 

[deweyville65]

Seriously, it sounds as if you starved the pump of oil for a short while. With 190k on the clock, you may have loosened some crud in the oil passage, and now have a plugged oil passage accounting for the increased valve train noise. However, I am stumped as to why it would be more noticable inside vs outside. As far as the pressure reading, probably a loose wire.

 

[toyotaspeed90]

Yeah - there's a slight concern for sludge. I'm going to be looking for signs of it when I replace the oil pressure switch. I'll get an adapter for the block then run a braided line to a bucket.. run it for a few seconds and see what comes of it. [turn it off] connect a gauge & rerun it to see what it's reading at.

the switch itself didn't have a loose connetion & I even tried rotating the wiring to see if by chance there was corrosion (or something) but there was no change on the gauge.

Hopefully today I can get the adapter needed before the hydraulic shop closes.


As for the tank comment - for off roading purposes that would be the FJ40 that went with me and basically idled up hills in 2wd while I struggled in 4wd.

 

[FIND]

First, get a mechanical oil pressure gauge on it. They may be entirely unrelated coincidences.

Tank, schmank. I've gone through things in 2wd trucks that many people would be afraid of in 4wd. I've driven loaded semis with trailers through fields right past people who were waiting for the tractor to come and pull their 4wd out. Off-roading isn't just what you are driving. My old explorer spent TONS of time off-road, and I didn't even know if the 4wd worked for over a year.

 

[toyotaspeed90]

First, get a mechanical oil pressure gauge on it. They may be entirely unrelated coincidences.

yeah... I have an autometer setup that I used on my MR2's... I just need an adapter from the block to the gauge. As it turns out I'm at work later than I wanted today so I won't make it to the hydraulic shop for the needed adapter. If I get really ambitious I might just pull the pressure sending unit, crank it over to see if maybe there's something caught in the port. Considering I have to replace the bellows in the boat this week I may not start working on the explorer yet.

I'm hoping they're unrelated. It wasn't like I was dumping oil anywhere to lose pressure (in fact the only thing I have is a very slight oil leak from a valve cover... and before heading out I even topped it off probably adding a bit too much).

I also had it idling yesterday and pulled the wires individually.... the noise was consistently there so I KNOW it isn't a rod bearing (for those that don't know - rod knock occurs when a bearing spins and the pressure from firing the cylinder will cause the rod/bearing to move & make the noise).

 

[toyotaspeed90]

so I bought a new sending unit - but didn't have time to run to the hydraulic shop for some adapters. Installed the new unit and oil pressure showed back up. started it to move back to it's parking space & the noise was almost gone.

took it around the block and drove it hard a bit - the gauge started to fluctuate again, but was more on than off. the noise came back but was much less noticeable.

I'm thinking of ordering the deltacams rocker arms & pushrod kit.... seems to be a good price and at least a starting point - won't require to pull the heads.

here's a couple shots:

 

[FIND]

If the gauge is fluctuation, you either have a pressure, or a wiring problem. If it is a pressure problem, buying rockers and pushrods is throwing money away until you fix the pressure problem.

 

[toyotaspeed90]

I'm aware. that's also why I ordered an electric oil pressure gauge kit. (I have a mechanical gauge but I don't like the idea of running a long oil line into the cab)

considering the truck's electrical issues I'm going to guess that is the more likely cause (since moving the truck had no change in pressure reading but swapping the sensor did). I've also determined that it's quite likely that the softer pushrods have worn in those 190k miles. Like I said earlier, I've determined it isn't a spun bearing (at least the noise) - and the noise does sound more from the top end. Even if it ends up being an oil pump that isn't necessarily going to stop me from checking the rockers & pushrods for wear.

 

[FIND]

Fair enough, sounds like you have a good plan.