intake gaskets? coolant leak, smoke test, codes, rough idle...

[rangerb4000]

Hello, I am trying to diagnose my truck before taking it apart or taking it somewhere. I believe it is lower manifold gaskets but would appreciate any input. I will do my best to explain what I've tried, and where I'm at.
Thank you in advance!

I got this truck in trade a few weeks ago, it's a 1999 mazda b4000 aka ford ranger 4.0 V6 OHV, ~165k.
CEL codes at the time were p0174+0171, running lean both banks, and p1506 IAC duty cycle high.
(also p0500 for vehicle speed sensor but assuming unrelated)

Looks clean under the hood and there appear to be new plugs, wires, and vac lines. fuel filter has also been changed. It was supposedly a daily driver and ran well at first, but RPMs were always higher than normal, which worried me. Then idle became rough, wanting to stall. heard whistling around the air filter box, changed loose air filter, disconnected battery and cleaned MAF and IAC with maf cleaner. after relearning idle, truck seemed to run perfectly at normal rpms for one day, then next day rough idle returned with surge/plunge/stall misfire that went away when engine warmed up. It was driveable locally for a few days.

Then (of course) coolant started leaking at the water pump weep hole so I took it to a shop, not wanting to tackle that in the single digit temps. asked them about the idle and they said it was acting like vacuum leak from intake manifold, but further diagnosis would be necessary. When I drove it home was running rough, always wanting to stall at low rpms.

Checked codes, and new ones were: P1131+1151 'lack of switches' indicates lean, P0113 Intake air temp sensor high bank 1, and p0136 02 sensor circuit bank 1 sensor 2.
(I believe all of these can point toward a massive vacuum leak? or bad MAF, but you'll see why I skipped that for now.)

When I started it the next morning, there was a new large steady leak of coolant below the rear of the engine, dripping from the bellhousing (pic below). Can't see exactly where it's coming from above that, but I am guessing somewhere on the passenger rear of the engine/compartment. There is nothing visually obvious that I can see from above. It's a significant amount of coolant dripping, only when truck is running.

I did a home-made smoke test (worked pretty well!) and smoke was coming up from beneath the coil pack. so a vacuum leak is definitely confirmed... I don't know if any vac lines run under there, if anyone is able to deduce more from the video, I'd appreciate it. (https://youtube.com/shorts/dJbWvDBLdvM?si=LvO8yW-GGNyr-Fie)

At this point I am pretty convinced that it is upper and/or lower intake manifold gaskets, and the leaky airbox hid it from me for a while, then when the coolant pressure was corrected, it finally blew an intake gasket... but I want to make sure I'm not overlooking another possibility. head gaskets? cracked heads? something like that? or a combination of unlucky unrelated things, like a bad MAF/IAC and a bad freeze plug...AND a vacuum leak?

Whether to attempt them myself is another question... it seems like a fair amount could go wrong with how much has to be taken apart, and a big job if that's not the problem.

 

[RobbieD]

Welcome!

And great first post; good detail on what you've got going on.

When I started it the next morning, there was a new large steady leak of coolant below the rear of the engine, dripping from the bellhousing. Can't see exactly where it's coming from above that, but I am guessing somewhere on the passenger rear of the engine/compartment. There is nothing visually obvious that I can see from above. It's a significant amount of coolant dripping, only when truck is running.

Although the "dripping from the bellhousing" part doesn't sound good, your truck may have (likely has) a heater core diverter valve in the upper passenger side of the engine bay. These commonly fail and leak coolant, so do check that, if only to rule it out.

Hang loose; there'll be better hands come along and comment on your intake gasket suspicions.

 

[rangerb4000]

Welcome!

And great first post; good detail on what you've got going on.



Although the "dripping from the bellhousing" part doesn't sound good, your truck may have (likely has) a heater core diverter valve in the upper passenger side of the engine bay. These commonly fail and leak coolant, so do check that, if only to rule it out.

Hang loose; there'll be better hands come along and comment on your intake gasket suspicions.

Thank you! will definitely check that in the morning. much appreciated.

 

[Brain75]

My biggest worry at first too was the coolant leak, thinking more head gasket than heater... If you can't for sure find the leak in the heater area I would not start it until you drain the oil and check for coolant in the oil... course the first and easiest check is what does the coolant level look like compared to last time you looked sideways at it - did it swallow a gallon in a day?

 

[Brain75]

oil floats on water, so the first thing to come out of the plug would be coolant if there is any in there.

 

[rangerb4000]

My biggest worry at first too was the coolant leak, thinking more head gasket than heater... If you can't for sure find the leak in the heater area I would not start it until you drain the oil and check for coolant in the oil... course the first and easiest check is what does the coolant level look like compared to last time you looked sideways at it - did it swallow a gallon in a day?

thanks for the reply! I haven't run it much since that leak, and coolant in the resevoir didn't seem to drop disproportionate to what was dripping out, as far as I could tell. I think it lost about a pint in the few minutes I've run it. will check level in the rad tomorrow. oil looked the same on the dipstick, just a little low, but good call to pull the plug. Will keep you posted.

 

[alwaysFlOoReD]

Frost plugs can have pinhole leaks. A flashlight and a mirror might help locate if so. Back of heads are where I found mine leaking.

 

[lil_Blue_Ford]

Also the heater box has a drain by the firewall. If the heater core is leaking, sometimes it leaks out there instead of on the passenger floor.

 

[rangerb4000]

Just a quick update.
No coolant leaks at the heater hoses or components anywhere along the firewall or top of engine compartment. definitely seems to be coming from somewhere on the back of the engine. leak is a slow but constant drip when truck is off (haven't restarted it).
put a mirror down there but couldn't see above the area in the photo...

also drained the oil, sludgy and bubbly coming out, with a brown tint in the sunlight.

 

[Brain75]

That seems to be an excessive amount of aeration in the oil for a cold engine that was sitting... if not aeration than suspended something... except coolant doesn't suspend it would be at the bottom of the pan..
If you haven't hauled it off, I'd put a 2L into a old clear soda bottle and let it sit overnight to see if anything separates out. I don't know what to make of that honestly... it doesn't look good, but I don't wan to panic if all it is is air bubbles from draining and falling 3' from a lift down to a catch pan far below it.

 

[rangerb4000]

That seems to be an excessive amount of aeration in the oil for a cold engine that was sitting... if not aeration than suspended something... except coolant doesn't suspend it would be at the bottom of the pan..
If you haven't hauled it off, I'd put a 2L into a old clear soda bottle and let it sit overnight to see if anything separates out. I don't know what to make of that honestly... it doesn't look good, but I don't wan to panic if all it is is air bubbles from draining and falling 3' from a lift down to a catch pan far below it.

thank you for saying that, I thought it looked strange also.
I didn't lift the truck to drain it, it was flowing from about 9" off the driveway. there was one ominous thicker glob in the stream early on. the oil is sitting in a clear container now, will inspect again tomorrow..
beginning to suspect a head gasket ... but also have no idea the age of that oil or history of the engine, maybe ancient and dirty or sludge from overheating previously or something else?

 

[Brain75]

well with a thicker glob dumping out that would settle it in my mind, I would be pulling the valve cover just to make sure what it looks like up there (valve cover gaskets are cheap and if they are in great shape can even be reused in a bind - they aren't high torque or much pressure sealing.)

On an oldie like my '48 I'd be dropping the pan too - same reason, pan gasket is cheap. But all of these have a crossmember in the way and it is too tight to get out without lifting the motor half way out of the bay.

There's been some fight back from the mechanic industry on oil change interval... Consumers (women) want their vehicle to need less frequent maintenance and mfg (Ford/Chevy/etc) are bowing to that and upping their maintenance interval to 7,500 even 10k on a lot of newer cars (like last 4 or 5 years)... mechanics are seeing a lot of sludged up engines.
Maybe as innocuous as the PO thinking he/she could push it to 7500 like the new ones do, "it can't hurt it". ooh yes it can... but it might be something worse, dunno without looking.
I'm sticking with 4k on my car and either 4k or 5k on the truck (5k cause it is easier to remember just looking at the odo, car has a reminder every 4k).

 

[Brain75]

before you yank a valve cover, I would grab a pair of nitrile gloves and go fishing in the oil to find out if that glob is a bit of plastic/rubber that got gobbed on with sludge and turned into a furball or something worse... stick a nice strong neo magnet in another glove finger and run it through the oil looking to see if anything sticks.

 

[alwaysFlOoReD]

You could send a sample to an oil analysis place like Blackhawk or similar.

 

[Brain75]

I see youtubers doing that a lot so it must not cost THAT much... have any idea what it costs?