HEAVY Leak from Oil Pressure Sensor?

[84720FourWheel]

That pressure sender leaked on my truck too. After several hours, my brother and I got it off without removing anything, but we had almost every kind of wrench you could think of. IIRC it was one of the S curve wrenches. 

So, about the Rotella.. Wouldn't 15w40 be a bit thick for winter? I'm not familiar with diesel oils. 

[datzenmike]

It sure would in Minnesota!!!! Not in Sacramento. If you change the oil twice a year try something 10W and add some ZDDP for the winter, change it out for the summer.

 

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[ggzilla]

Oh, and I ended up going with the ... Fram this time around. You should have seen the cashier's face at Autozone when he realized I was putting it in my truck. Somewhere between disgusted and horrified.

Cashier muy bueno.

[Hillbillybuddha]

So we got everything back together. We put the weber carb (that was on it when we bought it) back on. Man is it running like crap. I've searched for manifold leaks, vacuum leaks. I have an exhaust leak from that pipe that runs behind the engine block but I can't find my 23mm to tighten that one up. And it idles at 2k, if I try to lower the idle, she just dies. One of the reasons I changed the carb was because no matter what I did, I couldn't get the idle bellow 1k on the stock carb without it dieing or running really rough.

 

It's raining so Ivyracer will rebuild the stock carb while I work. We'll put the stock carb back on tomorrow and see how that works.

[IvyRacer]

No more oil leaking from the sensor (just the valve cover and oil pan *sigh*), but after we changed the oil to the rotella diesel, it blows thick clouds noxious smoke. We finally got a break from the rain to chase down all the vacuum leaks and play with idle and timing stuffs, but had to pack up and take a walk around the block to get some air. No matter what we adjusted, it idled low and crappy or 1500-2100 and "just ok"... but the smoke never went away.

 

I checked the dip stick before starting: not overfull

 

Oil pressure reads around 60-70 on the gauge (where it used to read at or below 45 with a bad sensor)

 

I changed the spark plugs and wires at the same time. Could mixing up some of the wires cause these symtoms?? I triple checked the order, and it appears to be right.

 

We shredded 2 3m non-scratch disc pads cleaning off the old intake manifold gasket, but any of those fibers would have finished burning off by now if they got into the cylinder, wouldn't they?

 

The only time the smoke eases up is when I reach freeway speeds. I cruise around 55mph with the tach showing about 2k. But any time I really push it (merging onto the freeway, or revving it while in neutral)... WHOOSH! Giant cloud of stinky, thick, smoke. WTH? Did I blow the head gasket somehow? HillBillyBuddha hooked up a vacuum gauge to measure the system pressure, and it seemed too consistent to be that. Did I get punked about putting diesel in my z24? Because what's coming out of the tailpipe seriously looks and smells like it's from a 30 year old semi.

[datzenmike]

Black smoke?

[Hillbillybuddha]

At idle it seems to be white to gray smoke but when you step on the gas, the smoke gets darker. 

 

I haven't done a compression test yet but I haven't noticed any oil in the coolant and the smoke doesn't smell sweet. I did hook up a vacuum pressure gage and the needle holds pretty steady at 19 psi at idle. (Any idea what the vacuum pressure should be at at idle? ) also, usually when I do a compression test, I pull all the plugs, on the z24 engine is it necessary to pull both sides or would just the exhaust side plugs be enough? 

[ggzilla]

Black / grey smoke is partially burned fuel

 

White with a bluish tinge is oil.smoke.

[datzenmike]

Yeah having the head off may have altered the carb slightly. Maybe the choke is stuck on.. is it plugged in?

[IvyRacer]

I would describe the smoke as blue-ish grey, getting darker/thicker when the engine revs. It is nauseatingly strong smelling, like two stroke exhaust. Very gas fumy. She's run rich since we started messing with the smog stuff, but this level of fumes is new.

 

We drove her about 100 mi yesterday in a mixture of freeway and heavy street traffic, and it smoked as I described the whole time. I didn't check the oil level last night when we got home, but this morning she started right up, no smoke, but tapping like she was low or nearly empty. Shut her off, checked, and sure enough the dipstick barely showed a "low" mark. I know now that it's leaking from the valve cover and oil pan, but with the sensor fixed, I only saw a small spot of oil under the truck. It seems I'm burning through oil faster than it used to leak out. Or, with higher oil pressure, it pushed more out through the remaining leaks while I drove all over town yesterday?

 

...and the carb is a whole separate issue. We got it from the salvage yard along with all the vac lines, canisters, egr valves, etc. We didn't know at the time that the plug on the side was so crucial. This truck doesn't have the o2 sensors or other systems to plug into this carb, so we left it dangling. I'm reading up on how disable it. The other option is using an adapter to install the weber back on with the stock air box. I don't like that the weber cuts out so many of the emissions systems though, and would rather stay as close to stock as possible.

[ggzilla]

Will the 720 feedback carb will OK in a non-feedback 720?

[IvyRacer]

Will the 720 feedback carb will OK in a non-feedback 720?

It seems to function, but only just. The choke valve has always stayed open as far as I could tell. I cleaned out the barrels while we had the intake and everything off, and blew more carb cleaner through it once we had it all back together and running.

[ggzilla]

It is like EFI, it has a duty cycle operated by the ECU. I always figured it would run full rich without the ECU.

 

I'm guessing you have three issues. Oil smoke, now combined with massive black smoke from the carb, plus the oil leaks.

[IvyRacer]

Just changed out the valve cover gasket. Wow what a mess. Oil pan gasket might actually be fine. There was enough oil seeping out of that brittle old thing to run down and make it look like the pan had a leak. I cleaned up as best as I could in the bay. PO was one silicone & liquid gasket happy sob! Looked like he tried to reuse the valve cover gaskets with a bunch of gooey crap. Ugh.

 

It was gnarly in there. No metal shavings or other damage, but everything was covered in a layer of sludgy soot. I dipped a rag in a pool of oil inside, and it smelled like gasoline. I'm going to change the oil a lot in the next few weeks :-/

[datzenmike]

If there is a failure in the feedback carb it will automatically default to a 'limp home' mode. This is an extra rich condition so that valves and pistons are protected from a lean melt down.

[IvyRacer]

I see. It sounds like other than my oil leaks, all my other problems are because we're using the wrong carb and HillbillyBuddha's threads are already dealing with that.

 

I'm going to change the oil and use regular 10-40 this time. Once we fix the carb problem, I may give rotella another try.

[MikeRL411]

What a beast that old sensor was to remove!!!  Even with the intake out of the way, it took all the strength and leverage I could manage just to get the first turn.  I messed up the hex so badly trying to turn my wrench in the tiny space (before we removed the intake and everything else to make enough room), I ended up using a vise-grip on the dang thing.  With enough room to get some leverage, it finally "just spun right off" like I imagine it's *supposed* to.

So, here's the old blankity blank sensor:

All the tool marks and abuse are from my frustrated attempts after trying with various wrenches for about 3 hours.  The attitude became "EFF IT, this one's broken anyway!!! Just don't mess up the threading in the block..."

 

This end was the sourse of the leak (it would spraaaay when the engine was under load, then just drip drip drip until she was nearly empty the rest of the time)

 

The hex was almost completely rounded out from multiple failed attempts to turn it in the small space.  I also believe the previous owner applied some kind of lock-tight or sealant, which made it even more difficult to turn even when I had the leverage I needed.

 

Here's the new one, snug as a bug.  I bought the lifetime warranty unit Autozone had for a wopping $60, but it was the only one anyone had in stock.  The threaded tip was slightly different than the one I removed.  It was a *tight* fit, and took a lot of patience to thread.  I felt like I cracking a safe :rolleyes:.  But once I caught that first thread, I was able to turn it the rest of the way with a wrench.

 

Now, the only thing keeping us from putting her all back together and taking a test drive is the remaining gasket that is baked onto the intake mating surfaces.  We have tried carefully scraping with razor blades (*shudder* my least favorite method for many reaons), and even let some "gasket remover" goop sit on there for a while and do nothing but drip all over a bunch of stuff I didn't want it to.  Finally had some success with a non-scratching 3m disc on a drill, but it took a whole pad just for one side.  Woke up to rain today, so it looks like this adventure is going to drag on a bit longer...

 

Be aware that British Pipe Thread [aka "ISO", International Standards Organization] is 27 threads per inch, while American Standard Pipe Thread is 28 threads per inch.  Which one is the 720 block tapped for and which thread does your sensor have?  I don't know from #$%^ what the 720 threads are, so take this as a caution to be checked if dripping reoccurs later.  There are available adapters from British standard to SAE NPT thread.  Looking at your clearance, I hope to hell you have the right sender thread, there's no room for an adapter.

[ggzilla]

Datsun blocks are BPT. Datsun senders are BPT. So no worries.

[datzenmike]

Nissan has run the BPT since it 'got into bed' with Austin in the early/mid 50's. It was still being used after 2000 and maybe still is.