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Discussion Starter #1
Just in time for Christmas... ok so I was leaving last night for the inlaws, about to get on the interstate when my transmission temperature gauge quickly went to the yellow. I pulled off to the side and sat there idling. Once it cooled off I shifted into all the gears everything seemed fine, got back onto the road and the temperature gauge gradually went to the yellow. Soooo slowly went home. This morning I dropped my transmission pan, replaced the filter, cleaned the magnet, reinstalled the pan and then did a transmission flush. I refilled with Merc V, drove around and then topped her off. No leaks, shifting fine. Backed up the truck and back on the road for the inlaws. Everything is shifting fine but for whatever reason after 50-55mph the temp starts to go up but if I keep it below 55mph then it says around 235 deg F. When I was on the interstate the temp went into the red, got off on the next ramp. No leaks so I am thinking maybe the fluid is low, it wasn’t low but I went ahead and added 2 more qts of merc V. Back on the interstate and same thing, after 55mph temp goes up. Got into the red one more time before finally making it to the inlaws ramp. Once off the interstate temp went down. I checked underneath again when I got to the inlaws and transmission fluid is everywhere toward the back. So did I just screw myself by over filling it? Do I have a blocked cooler? I checked and I do not have an inline filter. Bad pump? Help!
 

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It blew out fluid because you overfilled it by two quarts. Overfilling will also make it run hotter.

You either have a plugged cooler, or even more likely a bad bypass valve. You can get a rebuild kit for the bypass valve from Summit for about $25.

It's probably worthwhile to run a cooler flow test.

Warm the trans up. It should be at least 150°F.
Have two containers, each at least one gallon.
Get a hose that will fit over the cooler return line at the rear of the trans.
Remove the return line where it enters the rear of the trans.
Put the hose on the return line and put it into container #1.
Have a helper start the engine and leave it in park and at idle.
When the flow is steady out of the hose (that should only take a few seconds) move the hose to container #2 for EXACTLY 15 seconds, then put it back in container #1.
Shut the engine off.

Results:
If fluid sprayed out of the transmission, the test fails. A small dribble is fine, but spraying is not.
If there is less than a quart in container #2 the test fails.

If the test fails either the cooler bypass valve is stuck open or there is a restriction in the cooler circuit.
 

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Discussion Starter #3 (Edited)
When I did the tranny fluid flush it dribbled out but I want to go ahead and replace or maintenance everything I can. I have a cooler in the radiator and an aux cooler right? If the radiator cooler is blocked would replacing the aux cooler do anything? Could I try blowing compressed air in the supply of the radiator with the return line detached to see if that clears a blockage? I don’t know the routing of the fluid lines. I’ve had the 6.0 tranny cooler upgrade on my to do list and ill bypass rebuild to the job. When all the fluild came out do you think it damaged anything? Should I replace the pan gasket?
 

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Yes, in the 02 you have both the oil to water cooler in the radiator and the oil to air cooler up front. That cooler is undersized, but not towing you shouldn't have an issue. I think Mark is dead on with the bypass being faulty, but one other thing to check is your cooler fins and the radiator fins. If you've got 15 years worth of dead leaves and bugs in the coolers, they won't be doing much good. They're somewhat hard to clean in place, but you can take the upper shield off and loosen the condenser coil at the top and lean it forward to get pretty good access. Use a hose to spray off the big debris - even a soft bristle brush. Then try reverse flowing water through the radiator by getting up underneath and spraying from the back side. You can shine a flashlight on the back side while someone looks up front. If light isn't getting through, air isn't either.
 

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Discussion Starter #5
Where did all the tranny fluid come out of when I overfilled it? Is there a vent or is there a chance I blew out the pan gasket?
 

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No way to blow the pan gasket. The front seal will get soft and lose fluid when the transmission gets warm. Otherwise, if it was overfilled, it would come out of the vent.

I missed a question you had before. As to the routing - the front line from the transmission is the outflow line. From there it travels forward, to the radiator. Out the other side of the radiator to the air cooler. Out the other side of the air cooler and back to the transmission's rear line. You could blow air through the circuit, not to clean anything out, but rather to verify flow. Make sure and check to see if you have an inline filter in the circuit. Most likely, it would be in the rubber line that you see if you slide under the front just behind the radiator on the passenger side. I can take a picture if you need me to. If you do have that filter, and you haven't been changing it regularly, that might be the problem.
 

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Discussion Starter #7
I read the latest version of Kovalsky‘s instructions for tranny flush. I looked for an inline filter in the rubber lines but didnt find one. Just to verify could you send a picture of where your in line filter is located so I can double check?
 

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Discussion Starter #8
Thanks for everyone's advice. Got a bypass rebuild kit and 6.0 tranny cooler coming in. I still have a 2hr drive home (mostly interstate) so I am going to tap around the transmission, lines, etc maybe I get lucky and get that bypass valve to close or break loose the clogged lines. Any chance this is all a bad tranny temp sensor? Whats that part number?
 

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I try blowing compressed air in the supply of the radiator with the return line detached to see if that clears a blockage?
You can try, but if it's blocked this won't clear it.

Where did all the tranny fluid come out of when I overfilled it? Is there a vent or is there a chance I blew out the pan gasket?
It came out of the vent on top of the transmission. There is no way you blew out the pan gasket.
 

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Thanks for everyone's advice. Got a bypass rebuild kit and 6.0 tranny cooler coming in. I still have a 2hr drive home (mostly interstate) so I am going to tap around the transmission, lines, etc maybe I get lucky and get that bypass valve to close or break loose the clogged lines. Any chance this is all a bad tranny temp sensor? Whats that part number?
If you are on the road then the Bypass Kit is the project I would tackle before swapping out the 6.0 Cooler upgrade.

The Bypass kit is a 30-minute job. Pay close attention to the various o-rings. Make sure you locate each one you remove as a couple can get stuck in place.
 

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Discussion Starter #11
Thanks for everyone's help. This morning I took a small hammer and tap, tap, tapped away at they bypass valve. On the way home after church we took the interstate and I held 80mpg for a solid 20 minutes. The temp gauge didn't leave the half way spot. Hopefully it says that way so I can take the interstate home at the end of the week. In the mean time I have ordered a bypass rebuild kit, in line filter kit, and a 6.0 tranny cooler. I am considering a bypass delete kit, I live in South Carolina and never see cold weather. I know I risk destroying my tranny if the cooler clogs. I am thinking if I replace the in line filter regularly it wouldn't be an issue. What do y'all think?
 

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I have usually read of weak springs but yours almost sounds like the ball was caught on something or was blocked from closing if tapping it helped.

I am not a transmission expert by any means but I can't think of a good reason to delete the Bypass.
They serve an important function and they work 99% of the time and if they should fail then it costs under $20 to replace them and they are good for another 10+ years.

I do have an inline filter, a Magnefine and then there is also Raybestos from NAPA. I don't think they cause harm as long as they are changed out by 15,000-miles. Or did you purchase a more expensive external filter?

I have a 26-row 6.0 cooler (Ford brand) and according to my ScanGuage-2, it has brought my TFT down by about 20*F. I have never read anyone who thinks that mod was a bad decision or a waste of money.

Merry Christmas...hope you make it home without over-heating.
 

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I am considering a bypass delete kit, I live in South Carolina and never see cold weather.
What does never seeing cold weather have to do with this (poor) decision? The bypass is completely unaffected by cold weather. That's not it's purpose. It's sole purpose is to maintain flow to the lubrication system if the cooling circuit is restricted.
 

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Discussion Starter #14
OK so help me understand this. Previously my trans temp gauge was in the yellow when my TFT was about 160 degrees. On the way to my parents today my trans temp gauge stayed pretty much in the middle but my TFT was 220 degrees?! I am getting my trans temp via OBDII and DashCmd app.
 

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OK so help me understand this. Previously my trans temp gauge was in the yellow when my TFT was about 160 degrees. On the way to my parents today my trans temp gauge stayed pretty much in the middle but my TFT was 220 degrees?! I am getting my trans temp via OBDII and DashCmd app.
How long have you been using the DashCmd App?

Any chance you have any buddies with a ScanGuage-2 you could plug into the OBDII? That would let you test the DashCmd.

I am guessing you have not installed the Bypass yet with no deliveries over the last couple days.
 

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OK so help me understand this. Previously my trans temp gauge was in the yellow when my TFT was about 160 degrees. On the way to my parents today my trans temp gauge stayed pretty much in the middle but my TFT was 220 degrees?! I am getting my trans temp via OBDII and DashCmd app.
The gauge is designed to stay in the middle until the TFT reaches 230°F. I have no idea why it went there at 160°F.
 

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Discussion Starter #17
I will not be home until Friday afternoon, that is when I plan on working on it. I plan on doing the test where you get your transmission fluid to operating temperature and then disconnect the return line at the transmission and see how much it pumps, and then disconnect the return one at time at each cooler. I don't know anybody with a scan gauge... Hopefully when I rebuild the bypass valve and test the return lines I find something that clearly tells me what is going on.
 

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I guess if you test at the Trannission return line first and your flow is sufficient then you don’t have to test further upstream, eh?

Are you going to swap out your Bypass first?

I bought a Dash Cmd a couple years back and it reported TFT at 300*F so I got rif of it for a ScanGauge-2.
 

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Discussion Starter #19
Ya the bypass rebuild kit won’t be delivered until Friday afternoon but I will so that before running the test. So you are saying your dash cmd app told you the wrong transmission fluid temperature?
 

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Ya the bypass rebuild kit won’t be delivered until Friday afternoon but I will so that before running the test. So you are saying your dash cmd app told you the wrong transmission fluid temperature?
I purchased a Dash Command App in 04/2015 according to my records. It reported a very high (nearly 300*F) TFT at times. I don't know if it was the App or the OBDII connector but I quit using both within a couple days and switched to a ScanGauge-2 and it continues to work correctly and report correct values.

I don't know if that is a "part" of your problem or not but by your description in post #14 it appears you have atleast one gauge not functioning correctly and possibly mechanical issues as well.

I would say there is no harm in swapping out your Bypass Valve but do follow the instructions to the letter and watch that you remove each of the old o-rings and properly install the new ones since there are various sizes specific to various locations. Was it the Sonnax kit you ordered?

Instructions here: https://d2q1ebiag300ih.cloudfront.net/uploads/part/instructions/2078/36605-02K-IN.pdf?v=1491485793
 
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