4.0 Weird Behavior After Overheating

[Things2do]

Sorry about the wall of text, but I’ve already tried just about everything that I can think of.

For some background I bought a 1994 Ranger XLT 4x4 for $500 this summer. Clean title, 4.0, 5 speed, 192k miles, pretty much rust free, and supposedly it had a new clutch before it was parked for oil leaks 10 or 15 years ago. Including the tires, the battery, and the starter for which I had no core to return I’m about $1,500 into it in parts. The fan, water pump, and radiator were also missing, so I picked up an automatic radiator with the downward pointing lower hose connection from a junkyard figuring that the cooler might be useful as a power steering cooler in the future.

Last weekend I overheated it pretty badly. I managed to drive about 15 minutes across town without realizing that the lower hose had dropped off of the radiator on a speed bump because its clamp had failed. It was at least 50 degrees outside at the time. I checked all of the other gauges and lights once it started complaining under load, so I still can’t figure out how I missed the temperature gauge. From the sound of the pinging I thought something was coming loose around the clutch or in the transmission, and by the time I parked it even barely touching the gas in neutral was enough to make it ping. The offending bump had a nice antifreeze trail leading from it when I retraced my route that evening.

The engine got hot enough to burn off a lot of the oil from the valve cover leaks and the thermostat is now stuck open. I also think that the heat may have damaged the passenger side motor mount. I put the hose back on, replaced the clamp, waited 45 minutes or an hour for it to cool, refilled it with straight water, and then drove it all the way back without issue.

I’ve read quite a bit about the 4.0, so after driving for 15 minutes without coolant I figured that I had blown a head gasket and/or cracked a head. Well, the exhaust sometimes dumps an appreciable stream of water when revved while cold, and when it’s hot the exhaust randomly coughs and spits out a little steam cloud. Even though it isn’t visibly steaming the hot exhaust has enough moisture to make my hand damp with or without the little steam puff that comes with the cough. But the coolant level hasn’t dropped in either the bottle or the radiator since I got all of the air burped out after refilling it. The exhaust doesn’t visibly steam when it’s warm except for that random tiny puff that you have to be looking for, it doesn’t smell sweet, there is no water in the oil, there is no oil in the radiator, the radiator doesn’t bubble, the rubber glove test was motionless, and there isn’t enough blow by to lift a receipt off of the oil fill. It also hasn’t lost any power. I crawled underneath while it was running and from underneath the engine I can’t hear anything in the exhaust like the little cough that’s audible from the end of the tailpipe. I cranked it with the gas pedal floored to check the compression and it sounds even on all 6. I even misted the spark plug wires in the dark in case one of them melted and was shorting out.

Since it overheated the engine has been vibrating a tad more than it used to at idle, but not by a lot. Nothing like what it was doing before I replaced the old spark plugs and wires.

I have driven it 40 or 50 miles since that happened. I’ve been driving it hard trying to make whatever problems it developed become identifiably bad, but aside from sometimes running a little cool from the stuck thermostat nothing unusual has happened. In fact, after I ran about 60 MPH in 3rd gear for a few miles it almost seems like the exhaust is doing a little less of the coughing and the cold dripping than it was before that drive. I haven’t looked at the spark plugs or ran my little camera down the cylinders yet, but I don’t expect to find anything useful. Other than that I’m pretty much out of ideas. It still runs better than it did with the heavily worn copper spark plugs that it had when I bought it, so I don’t want to tear into the engine unless I’m pretty sure that I’ll find something in there. The check engine light has never come on. It's OBD1 and the bulb does work.

So… What should I check or do next? Or should I just replace the thermostat and then wait to see whether anything gets worse?

 

[bobbywalter]

you start by looking at the plugs.

likely just a good idea to replace them but they might just need cleaned up.

may have uneven valve sealing or some stuck/cracked rings now...or some minor cracks that are fine under normal conditions.

with the even cranking sound though, that is a pretty good sign. the rough running could be a minor vacuum leak from cooking it a bit. that unit should have a aluminum intake but possibly egr. this may have been affected by the heat cycle.

or it never really got too hot and your just freaking out.

they are sensitive to overheating though historically. the castings were better by 94 and then they went to a new setup with new issues.

if its running....and not consuming coolant and copius amounts of oil...and the oil pressure is ok at hot idle....like more then 18 psi on a real gauge...and its not crunching plugs its likely ok.

 

[superj]

the gauge stops reading temp when the fluid drains so you probably didn't miss it reading high, it probably just stayed at the temp it was at when the fluid dumped out.

i had the same thing happen on a jeep. the radiator cracked at the bottom and dumped the fluid. once the sensor tip is not in liquid, it stays where it last read. the whole time i was driving thinking all was good till it started knocking, just like you had happen

 

[bobbywalter]

the gauge stops reading temp when the fluid drains so you probably didn't miss it reading high, it probably just stayed at the temp it was at when the fluid dumped out.

i had the same thing happen on a jeep. the radiator cracked at the bottom and dumped the fluid. once the sensor tip is not in liquid, it stays where it last read. the whole time i was driving thinking all was good till it started knocking, just like you had happen

not really. it can see temp and will vary...still hot in there. ...provided it is variable...

 

[Dilligaf1]

Or should I just replace the thermostat and then wait to see whether anything gets worse?

That's what I'd do, and just not take any long trips for a couple months. Pull the plugs when you replace the thermostat, make sure nothing is burning lean or too rich. If it was still running rough after that, you could get a 1994 Powertrain Control/Emissions Diagnosis shop manual off of e-bay like This and start chasing down whatever sensor/valve that got partially cooked and is sending weird data. I couldn't even point to any direction because I could think of a half dozen things it could be just off the top of my head and you just be throwing parts at it.

 

[thesplash94]

I'd start with a compression test, followed by a cold coolant pressure test. If both of those checked out, let it ride and don't go far from home.

 

[Things2do]

Thanks, everyone.

I am planning on looking at the spark plugs when I have time. I replaced them 600 miles ago, so unless I find something wrong I probably won't replace them. If I can get ahold of one I'll probably do a compression test while I'm at it. I enquired about borrowing a compression tester last weekend and the guy at Advance told me to try AutoZone, but I haven't had a chance to check there yet.

The intake manifold is aluminum and there is no EGR. Something may be expanding and causing a warm vacuum leak though. I don't hear any hissing, but unplugging the IAC has little or no effect when the engine is warm. It almost stalls it out when the engine is cold.

I don't think it's burning any oil and it has yet to lose any coolant. I don't have a real oil pressure gauge but the top end isn't making low oil pressure noises.

It definitely got too hot, by the end it was pinging at anything above idle even in neutral. It burned off most of the oil from my valve cover leaks and that oil on the engine smoked for several minutes after I shut it off. The gauge went all the way to the white line just before the red line over the H. It is variable, and now that the thermostat is stuck open it slowly drops as I coast down long hills.

I know it needs an air filter, it probably needs a fuel filter so I'm going to do it too, and the first few miles after burning off all of the oil showed me that the valve covers are leaking a lot more than I thought they were. Is there a general preference on which valve cover gaskets I should get, or anything else that I should plan on doing while I'm in there? My covers are a little rusty but I think it's just surface rust. I don't seem to be having any trouble with either the intake gaskets or the injector O-rings leaking.

If I do get my hands on an oil pressure gauge, should I hook it up where the factory pressure switch is or is there a better place?

 

[bobbywalter]

Thanks, everyone.

I am planning on looking at the spark plugs when I have time. I replaced them 600 miles ago, so unless I find something wrong I probably won't replace them. If I can get ahold of one I'll probably do a compression test while I'm at it. I enquired about borrowing a compression tester last weekend and the guy at Advance told me to try AutoZone, but I haven't had a chance to check there yet.

The intake manifold is aluminum and there is no EGR. Something may be expanding and causing a warm vacuum leak though. I don't hear any hissing, but unplugging the IAC has little or no effect when the engine is warm. It almost stalls it out when the engine is cold.

I don't think it's burning any oil and it has yet to lose any coolant. I don't have a real oil pressure gauge but the top end isn't making low oil pressure noises.

It definitely got too hot, by the end it was pinging at anything above idle even in neutral. It burned off most of the oil from my valve cover leaks and that oil on the engine smoked for several minutes after I shut it off. The gauge went all the way to the white line just before the red line over the H. It is variable, and now that the thermostat is stuck open it slowly drops as I coast down long hills.

I know it needs an air filter, it probably needs a fuel filter so I'm going to do it too, and the first few miles after burning off all of the oil showed me that the valve covers are leaking a lot more than I thought they were. Is there a general preference on which valve cover gaskets I should get, or anything else that I should plan on doing while I'm in there? My covers are a little rusty but I think it's just surface rust. I don't seem to be having any trouble with either the intake gaskets or the injector O-rings leaking.

If I do get my hands on an oil pressure gauge, should I hook it up where the factory pressure switch is or is there a better place?

I am planning on looking at the spark plugs when I have time. I replaced them 600 miles ago, so unless I find something wrong I probably won't replace them.

when you over heat something and audibly knock it....always worth gawking at the plugs. especially with....you know...weird behavior after overheating.

 

[Things2do]

when you over heat something and audibly knock it....always worth gawking at the plugs. especially with....you know...weird behavior after overheating.

I finally had a chance to pull the spark plugs yesterday. 5 of them looked about the same, but one (passenger side closest to the firewall, I think that's #3) was brown. None of them had any cracks or chips anywhere, none of them had any weird buildup, the little platinum disks were both still present on all of them, and the gaps were within spec. My cheap little inspection camera disappeared when I abruptly had to move out of my apartment for a few days last month due to an upstairs pipe leak so I couldn't get a look down any of the cylinders. And I still haven't tracked down a loaner compression tester or oil pressure gauge.

I believe the stuff on the upper threads of the outlier is baked oil from the valve cover. Both of mine are leaking pretty badly and they get worse the closer you get to the firewall. I've lost almost 2 quarts in about 700 miles. The consumption rate didn't change when I overheated it. It isn't leaving any puddles on the ground, there's no evidence of oil smoke in the exhaust, the cylinders had good crosshatching when I put these spark plugs in a few months ago, and after it all got burned off I now think that a lot of it is coming out of the valve covers. The side of the engine around the exhaust manifolds went from almost dry to completely soaked with oil within 40 miles after I overheated it that day and burned all of the oil off.

A couple of the average ones:



#3, that chunk on the back of the ground strap is grease from the outside of the engine that got on when I pulled it out:


Since everything looked fine I hopped on I-70 and ran it 10 or 15 minutes up into the Rockies. After several minutes of climbing with it floored in 4th gear to hold 65... Nothing changed. The temperature needle never went past the M in "normal," it didn't lose any coolant, it didn't ping, it didn't misfire, no water got into the oil, and the exhaust still has the intermittent weird cough at warm idle. I also plugged the exhaust with my hand out of curiosity and got a good hiss from somewhere around the back of the muffler. That's around the first place where I can hear that cough, and it didn't seem to be doing the cough thing while I had it plugged.

If I remember right a darker plug is cold or rich, and since that one is identical to the other 5 plugs then that would point to what, a little injector trouble? It did sit for 9-16 years before I bought it, and all I have done to the fuel system is replace the tank and pump and bleed out the fuel rails until the gas coming out smelled normal. Except for the first few times when I first got it running and then that day while it was overheating it has never noticeably pinged or misfired.

 

[Things2do]

I hope you packed your reading glasses... Same truck, new problem, and another excessively long post.

I still have the same running a little off in open loop, but now it's significantly worse in closed loop. When it drops into closed loop it idles at about 600 RPM and runs roughly enough that you can see the plug wires and throttle cables and stuff vibrating, like it's constantly misfiring a little. It has also started overheating going up extended grades. It's fine around town, on normal relatively flat interstates, and on normal hills, but if I try to go up into the Rockies the temperature slowly goes up no matter if I’m on the interstate running 70 MPH or on a curvy 2 lane road doing 20 or 30 MPH. I haven't pushed the temperature gauge past the L in "NORMAL." I first noticed it on a winding, slow road and decided that my fan clutch was bad. It did come from a junkyard after all… So I went and did the stretch of I-70 going up from Denver to Evergreen knowing that I had done that without any issues since the day all of my coolant ran out. The temperature continued going up as long as I held the speed limit, but as it got close to the L I slowed down to about 40 MPH. Once I slowed down and wasn't working the engine as hard the temperature stopped going up and stayed where it was, between the A and the L. It didn't go up any more when I went back up to the speed limit on a flat stretch, but it also didn’t cool off until I got off and coasted down a hill. No matter if I’m doing 20 or 70, the temperature needle drops all the way back to straight up within a minute or two as soon as I coast down the other side with no load on the engine. The fan clutch seems to be cycling and operating normally at idle, both by sound and by feeling the airflow behind the shroud. It will sit and idle all day without the temperature going up any.

It also wouldn't stay running at first when I tried to come back down the mountain from that Evergreen trip. The first couple of times it acted like when you pull the intake tube off of the throttle body without unplugging the MAF, stumbling down until it died, as soon as it started. The third or fourth time I managed to keep it running with the gas pedal and took off for home. It had been parked for less than an hour. I haven't been able to replicate that issue.

I still have nothing setting a check engine light, no water in the oil, no oil in the radiator, and no unusual pressure in the radiator. I think it's a hair down on power near idle because I've stalled it on the street twice since this started. I hadn't done that in a long time prior to this. It still seems to have all of its power on the highway, although I can still feel an unusual vibration like a light misfire. I have gone up in the mountains with no issues since I dumped the coolant and overheated it at the beginning of this thread, so I don't think it's related to that incident.



Since I last went up into the mountains without issue the only changes are that I replaced the thermostat with a good one that isn't stuck open, I ran some Prestone radiator flush through it, I replaced the weak coolant with 50:50, I replaced the valve cover gaskets, I replaced the air filter, and my roommate plugged an OBD1 scan tool that he picked up at an estate sale into the under hood connectors. It's an OTC Monitor 2000. I also added a can of Berryman B-12 to a full tank of gas since it was cheap, it’s supposed to be good with varnish, and I’m sure there was still some in the fuel system with how long it sat. I’ve burned about half of that tank of gas and the vast majority of that was before this latest thing started.

I boiled the thermostat before I put it in and it's good. It's a 198, it started opening at 199 on my thermometer, it appeared to open fully, and it closed when I splashed some cold water into the pot. I boiled and cooled it several times before I put it in.

Adding fuel from an unlit propane torch into the intake made it run worse. Removing a vacuum cap raised the idle to about 900, but it was still running rough and it may have been a little rougher. Unplugging the IAC sometimes changes the idle, and sometimes it doesn't seem to do anything. Unplugging the SPOUT connector dropped the idle to about 500. As I expected, unplugging the octane adjustment connector thing made less of a significant difference. The throttle blade is pretty clean.



My roommate's scan tool worked fine on his '94 Chevy K2500, so he stuck the Ford connector on it and plugged it into mine. He had it plugged into my cigarette lighter which doesn't connect well because it's all gummed up. He put in my engine VIN, X, and he guessed R for the "series code." It wouldn't detect any live data, which I do have the pins for in my under hood connector, and the scanner shocked him pretty good once. H said it was a little more than normal static electricity, but not like an ignition coil or anything. He then ran a timing test while messing around to see what it would do. That test ran through itself twice. I read the book on it later and I believe that it should have set the timing to the 10 degrees like removing the SPOUT connector does for the first run through, and then for the second it should have returned to normal to let you check the advance. It didn't noticeably change on the first one, but on the second one the engine jerked once. I don't know what it did there as I was standing towards the rear at the time, but the timing may have advanced too far and detonated once.



So... Now what should I do? I'm thinking about running the KOEO and KOER tests to see if anything might come up and then, if not, trying to back probe anything electrical that might be remotely related to see if anything seems strange. I have the CHARM.li copy of the manual, I have access to a good digital multimeter, and I think I can swipe borrow a 2 channel laboratory oscilloscope for a little while if I need to. The radiator should be clear, the hoses are all new, the heater works well, and the water pump is not rusty or anything.

After I typed most of that out I put in a new Motorcraft fuel filter. The old one was a NAPA with an early 2005 date and stale smelling mud colored gas came out of the inlet when I shook it. That seems to have helped the rough idle some, but it's still a little rough and it still starts heating up if I try to go up a mountain.



This is the exhaust cough that I've been talking about. The loudest one is a little over 5 seconds in. The steam was just because it was cold outside and the engine and exhaust were still cold, it clears up as it warms up and it doesn't do it at all when it's warm outside. It still does this in open loop.