Reverse-Blew AT LP Port to Clear Pump Strainer
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6th Gear
Joined: Nov 2004
Posts: 6
Likes: 1
From: NC
Reverse-Blew AT LP Port to Clear Pump Strainer
SYMPTOM: This past week I've been eating, breathing, and sleeping TL transmission, since it started loosing ability to shift or engage after 30 min. of operation. Then days later, it would fail 15 min. after having the engine shut off for 45 or more seconds. Then 5 min. I consider myself a good 'driveway mechanic', I have the Acura Service Manual (all 15 pounds of it), and found LOTS of great help here in this forum, especially about understanding the AT Filter situation, and how to do a proper 3 x 3 flush. Yet yesterday, after a week of work, my tranny lost all ability to shift or engage, even cold.
CAUSE: Owner negligence. Yup, I own it: driving over 125K miles after my transmission recall/replacement, without once changing any ATF.
ATTEMPTED: After the first 3q flush, there was no sign of metal or particulates in my strainer, but the fluid was blacker than any ATF I've ever seen. Clutch dust from thousands of gear-shifts had turned the ATF into tar. 6 cleaned and tested solenoids later, and 2.5 gallons of ATF and 5 days later, I was still getting some dust in the drainage, but it had mostly cleared up. Yet the problem continued to get worse during testing.
DIAGNOSIS: Yesterday I got an oil pressure gauge with a removable hose, and connected it to the AT LP (Line Pressure) Port. This is described in the manual under "Pressure Tests", and this port gives access to the output of the ATF Pump. The pressure gauge confirmed that the ATF pump was indeed loosing it's pressure, slowly, after several minutes of warm-up time. And when the pressure dropped below 60 psi (120 psi service limit), the tranny would not engage. Also, the needle on the gauge bounced wildly +/-30 psi during all testing. At this point I can shut the engine off for 45+ seconds, restart it, and pressure would rise back up to a healthy 120 again, only to drop again after several minutes. ATF Pump is definitely the problem, or more likely, the internal strainer it sucks from.
ATTEMPTED: I decided to try and flush ATF through the LP Port, hoping that fluid velocity might open up a clog in the suction side. I unscrewed the gauge from it's hose, clamped the hose end into the opening of an empty 1 gal. ATF can, and started the engine in Park. All 3 quarts came shooting out of the pressure line in about 3 minutes' time. Then I screwed the gauge back on, poured the ATF back in, and ran it again. About 6-8 times total, I ran the same 3.5q of ATF through my tranny, out the LP Port, into the ATF can, back into the tranny. I was hoping I would see ATF stop getting blacker, and the clog stop killing pump suction. But at the end of the day... the tranny was completely useless and would not engage at all, ever.
AT LAST: Then I remembered I had a small air tank, capable of holding 150 psi. I had the idea to blow compressed air into the line attached to my LP Port, to provide a reverse flow, which should more easily remove any clog. So I filled the air tank, and found a coupling that let me blow air at 150 psi into the LP Port. I heard it gurgle a little inside the tranny case. After letting the tranny cool completely, I did the reverse blow again for about 5 minutes, then cold-drained the fluid. This was the first time I saw anything chunky come out in the fluid. There was some black, flaky crap at the bottom of my strainer. I can add a photo of it later.
Then I re-filled the ATF and screwed my pressure gauge back on it's line to the LP Port. Testing showed my pump held 120 psi pressure even after a half hour (of idle in Park). It still shifted 30 min. later. It was fixed! Mostly....
I went a step further, and performed a reverse-blow to the LP Port a few more times, but this time doing it into a drained AT case, and using brake cleaner (then carb cleaner when that ran out) as the flushing fluid. Simply squirt the cleaner right into the 5-foot-long pressure hose, then push it through with a few minutes of 150 psi compressed air. Then to clear out the cleaner fluid, I squirt ATF into the line and pushed that through with compressed air. Twice. All this is draining immediately out of the empty AT case.
After this, I gave her 3 quarts of fresh ATF, and screwed my gauge back into the line, and started the engine. WHO-HOOOO! I JUST SAVED $3,000! :-) The pressure gauge ran right up to 125 psi, and did not vibrate at all during my 30 minute test. At the end of 30 minutes there was 0 sign of degradation. I'm a happy guy right now, because I just got back from a 45-mile test drive, and the tranny worked perfectly in all gears.
So... if this happens to you.... you can skip the hours of messing with solenoids, flushes, LP Port flushes, and proceed directly to the LP Port reverse-blow.
I've read and heed lots of precaution in this forum about using pressure flush on our 2G Acura TL trannies. So I would not recommend using any higher pressure than 150 psi. By blowing into the LP Port, you avoid pressurizing all the spaces inside the tranny, where you have important seals and gaskets, so I felt safe doing it to mine.
CAUSE: Owner negligence. Yup, I own it: driving over 125K miles after my transmission recall/replacement, without once changing any ATF.
ATTEMPTED: After the first 3q flush, there was no sign of metal or particulates in my strainer, but the fluid was blacker than any ATF I've ever seen. Clutch dust from thousands of gear-shifts had turned the ATF into tar. 6 cleaned and tested solenoids later, and 2.5 gallons of ATF and 5 days later, I was still getting some dust in the drainage, but it had mostly cleared up. Yet the problem continued to get worse during testing.
DIAGNOSIS: Yesterday I got an oil pressure gauge with a removable hose, and connected it to the AT LP (Line Pressure) Port. This is described in the manual under "Pressure Tests", and this port gives access to the output of the ATF Pump. The pressure gauge confirmed that the ATF pump was indeed loosing it's pressure, slowly, after several minutes of warm-up time. And when the pressure dropped below 60 psi (120 psi service limit), the tranny would not engage. Also, the needle on the gauge bounced wildly +/-30 psi during all testing. At this point I can shut the engine off for 45+ seconds, restart it, and pressure would rise back up to a healthy 120 again, only to drop again after several minutes. ATF Pump is definitely the problem, or more likely, the internal strainer it sucks from.
ATTEMPTED: I decided to try and flush ATF through the LP Port, hoping that fluid velocity might open up a clog in the suction side. I unscrewed the gauge from it's hose, clamped the hose end into the opening of an empty 1 gal. ATF can, and started the engine in Park. All 3 quarts came shooting out of the pressure line in about 3 minutes' time. Then I screwed the gauge back on, poured the ATF back in, and ran it again. About 6-8 times total, I ran the same 3.5q of ATF through my tranny, out the LP Port, into the ATF can, back into the tranny. I was hoping I would see ATF stop getting blacker, and the clog stop killing pump suction. But at the end of the day... the tranny was completely useless and would not engage at all, ever.
AT LAST: Then I remembered I had a small air tank, capable of holding 150 psi. I had the idea to blow compressed air into the line attached to my LP Port, to provide a reverse flow, which should more easily remove any clog. So I filled the air tank, and found a coupling that let me blow air at 150 psi into the LP Port. I heard it gurgle a little inside the tranny case. After letting the tranny cool completely, I did the reverse blow again for about 5 minutes, then cold-drained the fluid. This was the first time I saw anything chunky come out in the fluid. There was some black, flaky crap at the bottom of my strainer. I can add a photo of it later.
Then I re-filled the ATF and screwed my pressure gauge back on it's line to the LP Port. Testing showed my pump held 120 psi pressure even after a half hour (of idle in Park). It still shifted 30 min. later. It was fixed! Mostly....
I went a step further, and performed a reverse-blow to the LP Port a few more times, but this time doing it into a drained AT case, and using brake cleaner (then carb cleaner when that ran out) as the flushing fluid. Simply squirt the cleaner right into the 5-foot-long pressure hose, then push it through with a few minutes of 150 psi compressed air. Then to clear out the cleaner fluid, I squirt ATF into the line and pushed that through with compressed air. Twice. All this is draining immediately out of the empty AT case.
After this, I gave her 3 quarts of fresh ATF, and screwed my gauge back into the line, and started the engine. WHO-HOOOO! I JUST SAVED $3,000! :-) The pressure gauge ran right up to 125 psi, and did not vibrate at all during my 30 minute test. At the end of 30 minutes there was 0 sign of degradation. I'm a happy guy right now, because I just got back from a 45-mile test drive, and the tranny worked perfectly in all gears.
So... if this happens to you.... you can skip the hours of messing with solenoids, flushes, LP Port flushes, and proceed directly to the LP Port reverse-blow.
I've read and heed lots of precaution in this forum about using pressure flush on our 2G Acura TL trannies. So I would not recommend using any higher pressure than 150 psi. By blowing into the LP Port, you avoid pressurizing all the spaces inside the tranny, where you have important seals and gaskets, so I felt safe doing it to mine.
Thread Starter
6th Gear
Joined: Nov 2004
Posts: 6
Likes: 1
From: NC
This shows the 'flakes' drained after back-flushing the LP Port (Pump). In multiple flushes, I've removed about 5 times this amount. It doesn't come from drive-testing, only from back-flushing my pump.
OVER-FLUSH: Yeah, who'da thought? My first test drive (after back-flush) was to the auto parts store, where I picked up a can of Sea Foam, hoping to get a maximum gunk removal before my last 3 x 3. My second test drive, with a can of Sea Foam in the case, left me stranded on the side of the road, 4 miles from home, with a completely disengaged transmission. The pressure gauge confirmed the pump was clogged all over again, and the ATF, which I had thought was about 2/3 of the way cleared up, was now a dark black-burgundy again. I had to do a road-side back-flush and drain to get home again. The instructions on the can had said to pour it in and drive 100 mi. then drain. Well my ASM (Automatic Sludge Maker) only made it about 30 miles. I should have kept this flushing exercise to driveway testing.
Anyone else ever use this stuff? Trans Tune | Fluid Treatment for Transmissions, Hydraulics & Power Steering (seafoamworks.com)
Since then I've back-flushed lots of air and ATF through the pump, and I'm not getting flakes anymore, plus the ATF is clearing up again. I think I'm about 2 more changes away from a clean transmission.
Thread Starter
6th Gear
Joined: Nov 2004
Posts: 6
Likes: 1
From: NC
At the risk of getting sucked into the ATF wars, I'm flushing and running with Valvoline MaxLife for Imports. But if I had known in advance how much fluid I was gonna burn through this month (11 gallons)... I'd have started with the cheapest stuff on a WalMart shelf.
Beware the Sea-Foam. Just when I thought my fluid was clearing up, Sea Foam completely re-gunked my tranny all over again. Meaning that it did an excellent job.
Beware the Sea-Foam. Just when I thought my fluid was clearing up, Sea Foam completely re-gunked my tranny all over again. Meaning that it did an excellent job.
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