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Our X has got me stumped. After shutting it down for 4 months to rebuild everything under the timing cover (yes I know it shouldn't take that long), I did a poor man's flush. It seemed like, according to our BullyDog, the engine was running warmer, but not hot, and the same with the trans. The trans kept running hotter as time went on (days, weeks) and on the last trip I towed a utility trailer (maybe 1000lbs) and on the last (18 mile) leg of the trip it ran hot enough I had to shut it down 3 times, the last of which temped at 275. Trans fluid is black. Oh, and at low RPM (idle) it developed a whine that I THINK is the trans, it had been doing this off/on since the 4 month shut down. I've got maybe 300 miles on it since the shutdown when I did the timing cover stuff and the PMF.

Today I dropped the pan and cleaned out the sludge. The screen was plugged as well (or very dirty). I read several threads on the trans here, and most said no need to worry about that screen since it's not a filter. I have to disagree. I'd suggest anybody with over 75K (our rig has 115) drop the pan and change the filter. O'Reily auto parts has the correct filter listed, which cost $20 with a pan gasket included.

Now the interesting part... I was going to do another flush today, and in the process of doing so, discovered I've got ATF coming out of BOTH ends of the hose! I disconnected the hose from the air cooler to the solid line, and have fluid coming out of the solid line, and the flex line that went to it. How can that be? Isn't one of trans ports just a dump into the case?!?!?! That's got to be why it ran hot. When I start it, I get fluid out of one line, a delay of a few seconds, then fluid out of the other line. Both streams are old black fluid.

Anybody have insights as to what's going on? A fix? A...<groan> prognosis? I really don't like the idea of dumping another 3-4K into this truck, the thing got dubbed the Lemon and it's trying to live up to its name.
 

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Discussion Starter #2
Update... The first outing with the new screen/filter, was a flop. 35 miles round trip with a 20 minute shutdown at mid point yielded *260 according to the BullyDog.

When I got back I checked with an IR thermometer and it was showing around 220 at the pan, so it's not just an indicator problem. I quickly pulled the grill (I do like that about the X, 4 snap 'rivets' on top, and 4 clips on the bottom, poof, instant access. The air-trans cooler is showing 100-120, I'm thinking I have a major flow issue.

Next up... Back into the trans, drop the valve body, clean the solenoids, and check them with a meter to see if any of them (especially the one for coolant control) are bad, but I would have thought the computer would catch that.

Anybody have other ideas other than... <beep beep> Take it to Amco? Which I'm starting to think, at over $100 a whack for ATF for this thing, is starting to look cheap!!!
 

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Did you kink a hard line when you had it apart?
I have known rubber hoses to break down internally and cause a blockage. Really bad if fuel hose is used instead of transmission cooler hose.

Really a million little things it could be. IF you pull a hose off the cooler and start it, does it pump a lot of fluid real fast, or just a trickle (indicating a restriction somewhere in the system)
 

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What I find kind of odd is that I'm getting fluid out of both lines. It's not a huge gush like I remember from the PMF I did when we originally got the truck and it takes probably.... 20 seconds per quart now, which I'd swear is slower than the last time.

I didn't touch the hard lines but I'll check them anyway.

Considering the amount of metalic sludge that was in there, I'm thinking the cooling solenoid is plugged up and bypassing all the time. But... That doesn't explain why it takes so long to warm up.

Thank you for your reply.

Chris

Did you kink a hard line when you had it apart?
I have known rubber hoses to break down internally and cause a blockage. Really bad if fuel hose is used instead of transmission cooler hose.

Really a million little things it could be. IF you pull a hose off the cooler and start it, does it pump a lot of fluid real fast, or just a trickle (indicating a restriction somewhere in the system)
 

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Based on the gradual nature of your problem, you definitely have a blockage somewhere- like a blocked artery, it is killing your transmission. I'd get it fixed ASAP, or you will be looking at a rebuild...
 

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Update: I've pulled the valve body and separated the two halves. I'll post pictures sometime soon but there are two check valves in there, and 4 filter screens. Surprisingly even with all the goop in ours, the screens look like they're clear.

I've been doing research and there are 3 versions of the valve body in that trans, and all three have been known to come with, or without, the cooler bypass valve. Our truck happens to have it, yours may or may not.

The valve is intended to bypass the coolers in the instance that they happen to get plugged. Why? I have no clue, I'd rather blow a cooler line than roast the tranny, though neither is a good thing.

I've already blown the lines out every which way I can except from the inside of the trans outward, which I'll try doing tomorrow.

I tried running the truck with both trans hard lines dumping into a container and got GOOD flow, like I remember it from my first PMF about a year ago. When I hooked the cooler back up, it was back to how it was before.

The bypass valve is known to wear, and cause problems exactly like what I'm seeing. The strange thing to me is how fast it happened, which makes me think that I somehow got 'stuff' in the lines when it was apart for 4 months.

OK, I'm done rambling for now. Hopefully, someday, this will save someone else some headache. :)
 

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The valve is intended to bypass the coolers in the instance that they happen to get plugged. Why? I have no clue, I'd rather blow a cooler line than roast the tranny, though neither is a good thing.
Sounds like you fixed it... great! I disagree on the above point though- if you blow a line, you could run the transmission dry very quickly, which is a lot worse it than just not being cooled (especially since it goes into limp mode at 275 degrees, giving you a warning before you burn up the clutch packs.)
 

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True about the limp home Vs. running dry. Personally it's like... 6 of one, half a dozen of the other. I had a TH400 blow the line and run (mostly) dry while on side streets. I did a quick repair and limped it a couple blocks to get ATF, and it never had a problem. Granted, that was an old school, HD trans, not the... <ahem> prissy little primadonna in the Xterra.

I wound up making a plug out of aluminum that fits where the cooler bypass valve and spring went. Does it cool now? Yep, much improved. But, it threw a P0744 today, on its 2nd outing (the first was around the block). P744 is... lock up converter intermittent. So, now temps are more normal (still a little warm, but maxed out at 180-190 on the fwy, going uphill in OD, and 208 on dirt. I don't know if I'll take it to a shop this time around, or if I'll pull it apart again, in... say... a few weeks to a few months.

I cleared the code but won't be driving the truck for another week so won't know until then if it comes back or if, perhaps, the 'crud' cleaned itself out. I'm kind of wondering if my bypass changed the line pressure and made it unhappy.

I'm soooo sick of this truck at the moment. The more I deal with the late model stuff, the more I like early fuel injection for off road and <gasp> carburetors for on-road.

Sorry(kinda) for the rant, I'm just really tired of the X at the moment. If I didn't have a good chunk of change in it in parts, I'd probably dump it. $1k under the front engine cover, $1200 or so in almost new tires, $500 or more in the trans (just in ATF!!!!), had the rear diff rebuilt $600 and it still whines because the gears have a wear pattern in them, and you can't find new ones. I think if someone walked up and offered 8K for it, I'd be very very tempted to get rid of it.

On the up side, it runs, and drives, and I'm leaving it like that for a while, while I cool down. :iconbiggrin: And when I look at SCCX videos I'm like: I wanna go!!!

So that's the most recent update, I'll keep yu' all posted.
 

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Fixed? I don't think so... As luck would have it, on my way home from buying a D60 front axle for our Jeep, the Xterra (LEMON!) died... And coasted to... A transmission shop, in of all places, Pinon Hills, CA.
The owner is telling me he'll rebuild it if he can but if it's going to be more than 2K (total) he'll just put a 'good' used unit in. Price wise, I can definitely deal with that, since I've been doing a bit of looking and used trans are running.... 1600 (I only looked for a few minutes). So 2K, installed, done, sounds pretty good.
It quit while running (engine stopped). According to the trans guy, the torque converter seized... Not sure about that one. Or the front pump.
I do know it was did a couple of odd things this trip, and I forced it to go as far as it did.
One of the oddities was when I pulled over, the Bullydog wasn't reading the trans temp, it showed 0, and it wasn't even trying to start (no click). After it cooled some, it would click, and trans temp reading came back.
Anyway, I'll update this thread after I get the Lemon back.
 

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I wound up borrowing my Dad's Avalanche, and renting a trailer to drag the Lemon to a local transmission shop. It took 2.5 weeks and $4,000 to get it fixed.

They used the starter to slowly bump the engine over (it would barely move when the starter hit) so they could get to all the converter bolts. Turns out the torque converter was seized to the input shaft, they had to pry it off with 2 bars when it was on the bench. Yep, valve body was cooked too. The computer never did go into limp-home on me, I don't know why if it was hot enough to start melting plastic parts.

Anyway, it's back on the road... 3/36 warranty on the trans, new radiator, and a new (aftermarket) trans cooler in place of the factory one.
 
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