Frustrating C4 leak - Page 2 - Ford Mustang Forum
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If you pull the pan off you will find that the tube will sit about 1 inch into the casing just above the pan bolt level and the dipstick about 3/4 inch further again.
Have a look at the picture down in the bottom right hand corner. You can just make out the tube and the dipstick.


15/5/1964 260 Manual Coupe.
23/3/1965 289 Manual Fastback.
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... ya, that's about what mine looks like... The end of my tube is 1/2" above the pan bolt level (or 1" into the trans) & I can read the word 'ADD' on the dipstick (3/4") - the second 'D' just clears the tube. SO - that means that the FULL/HOT level definitely sits higher than the pan by nearly 1.5", or just below where the DIP tube meets the trans. That about right?

Good to have that confirmed... If only I knew why/how to stop the drain back into the overflow/vent tube... I can't believe that is considered 'normal'...

R.R.

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I have never had any issues of fluid bleeding through the vent tube along side of the casing. Maybe that is why Ford introduced the breather on top of the casing on later years.
I would be checking if you have the correct year dipstick as the only reason it would overflow is if the fluid level is too high or that your filter has a slight blockage stopping the fluid draining to the pan quickly.

15/5/1964 260 Manual Coupe.
23/3/1965 289 Manual Fastback.
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Ya, filter is as clean as a whistle... It only comes out the vent after sitting for a few days or more of not running. My car is cold stored in the winter... when it hits -20C out, then there's a massive lake of ATF on the floor. More than a little annoying to have to keep a pan under it.

Some of my forum research suggests the cooler or torque converter is draining back past a check valve, but no one knows where this mystery check valve is & if it is easy to get to/fix...

The hunt continues...

R.R.
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Quote:
Originally Posted by cuddyk View Post
Thanks Guys. FWIW, I'm using only Type F ATF and the dipstick is showing full at idle, as normal.

I know how to drop the transmission no prob, but I've only worked on Porsche 901s. I'm pretty good at wrenching, but how much skill is required is it to overhaul the C4 and replace the seals as a DIY? Any special equipment required? Or is this one of those things best left to the pros?
You need a set of retaining clip pliers (inner and outer) a clutch pack compressor, basic tools and a clean flat surface to work on with good lighting, I use a 3' x 7' stainless steel table.



https://www.amazon.com/Rebuild-Modif...4+transmission

You can do it yourself for around 125.00 to 150.00 if you need to buy the special tools and rebuild kit or let a shop do it for around 600.00 to 750.00 and they may do it well or may not.
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Adding back on to this thread as my C4 leak has returned. Same story as the OP. No driveability issues, no drips when driven on a regular basis (I probably drive it every other day), however as soon as it sits for a period of time the leak starts up again. This time it took almost a month for the issue to show up. Now that it's put away for the winter I'm certain I'll be down a couple quarts when Spring arrives.

Pan and gasket, as well as dipstick tube have all been replaced. Mechanic says it's not coming from the shift shaft seal. I do see it collecting on the driver side rear bolt of the pan before dripping though. It's hard to say for certain as I can't get very far under the car due to it's low height and the headers. I'm pretty confident is coming up from above the pan.

I'm to the getting to the point where I am thinking rebuild or replace. Whatever I do it's going to have to wait until Spring. I've searched for hours on this topic and it seems to be quite common. If it is the torque converter draining back is the answer a catch can?

It seems amazing to me that so many people have this problem, yet a permanent solution can't be found. I realize I'm being a little dramatic, but I'm getting to the breaking point.

Talk me back from the ledge!

*Rebuilt 302 and likely the original 1965 C4 Auto
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John, while it's common for these to leak, I'd say that 99% of them leak from the same three places, and you already know them. The filler tube, pan gasket, and shift lever seal. With those three areas addressed, either the problem got 'messed with but not fixed', or else you have a "weirdo" problem that isn't very common!

Some of the fluid in your converter will drain down over time, sure. But even with elevated levels of atf in your case because of that, a C4 with good seals isn't prone to leakage. So basically, that's a "problem" you don't need to fix.

The most infuriating thing about these leaks is the simple fact that the fluid runs down and drips off at a place that may not be close to where it originated, and it's difficult to find the trail unless the whole thing's spotlessly clean to begin with. But I do wish you the best of luck in finding it!

I smile a lot. It makes people wonder what I'm up to...
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Where is that 'how to' on c4 shifter o-ring repair? looked for 'sticky' and also did searches in the forums......thanks
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... I've been working at my C4 over the last few weeks... I drained the pan & removed the filter/gasket, speedo gear, yoke & trans case cooler line adaptors (waiting on replacements to come). I was tracking leaks at the rear cooler fitting (o-ring was shredded), rear seal (yoke worn & 'tool marks' on it) & over flow/vent tube. Since I don't have all of my parts yet, I put the pan back on loose with 2 bolts. I originally dumped about 4 quarts out. It holds 8 total & half of it is in the converter, that makes sense. HOWEVER - I've been back under it a couple times since to check on things & I am still able to empty the pan each time. My catch pail has got close to 6-7 quarts in it now, so I'm guessing there's just what's left in the lower half of the converter in it now that won't likely escape. Last time I dumped the pan there was only a few ounces. So, definitely some drain back happening. From all the research I've done, it seems the drain back preventer valve is a spring & ball, or spring & a piece rubber located in the pump - behind the converter. It seems the solution is to remove the trans & either rebuild or replace the pump to solve the problem. I'm not prepared to do that just yet, so I installed some 5/16" clear tubing over the vent tube up to the master with a 'candy cane' on it to keep dirt out. The idea is, the fluid can travel up the tube, but won't go any higher than the high point which is either the top of the cooler or torque converter & it an get sucked back in when the vehicle runs. I'll also be ale to see if anything is/has been in the tube.

That's what I got so far...

R.R.
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Quote:
Originally Posted by Tbohann View Post
Where is that 'how to' on c4 shifter o-ring repair? looked for 'sticky' and also did searches in the forums......thanks
It's at the top of the forum listing. Here's a direct link:

https://www.allfordmustangs.com/foru...-solution.html
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Quote:
Originally Posted by John3020 View Post
Adding back on to this thread as my C4 leak has returned. Same story as the OP. No driveability issues, no drips when driven on a regular basis (I probably drive it every other day), however as soon as it sits for a period of time the leak starts up again. This time it took almost a month for the issue to show up. Now that it's put away for the winter I'm certain I'll be down a couple quarts when Spring arrives.

Pan and gasket, as well as dipstick tube have all been replaced. Mechanic says it's not coming from the shift shaft seal. I do see it collecting on the driver side rear bolt of the pan before dripping though. It's hard to say for certain as I can't get very far under the car due to it's low height and the headers. I'm pretty confident is coming up from above the pan.

I'm to the getting to the point where I am thinking rebuild or replace. Whatever I do it's going to have to wait until Spring. I've searched for hours on this topic and it seems to be quite common. If it is the torque converter draining back is the answer a catch can?

It seems amazing to me that so many people have this problem, yet a permanent solution can't be found. I realize I'm being a little dramatic, but I'm getting to the breaking point.

Talk me back from the ledge!

*Rebuilt 302 and likely the original 1965 C4 Auto
John, I had a similar leak but dripped all the time. The puddle several drops everyday.
The leak was identical to yours, After many gaskets and trouble shooting the leak was coming between the bell housing and the transmission body, running down the casing, along the pan and drip from the left rear pan bolt. (Not inside the bell) I believe it is an O ring on the main input shaft.
Drove me to insanity.
Here is my thread with a picture if you care to read it. https://www.allfordmustangs.com/foru...nsmission.html

I fixed it though, I put in a 4 Speed toploader. Best decision I made.
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15/5/1964 260 Manual Coupe.
23/3/1965 289 Manual Fastback.
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Grimbrand, R.R, and Tony,

The responses and empathy are greatly appreciated. I'm a novice at best when it comes to some of these issues, but I am willing to learn. Part of my frustration is not actually seeing where the leak is coming from, so reading about the common trouble areas is definitely the education I'm hoping to use when taking it back into the shop in this Spring.

R.R. and Others: This catch can method intrigues me. I've seen others mention it and the guy at the shop said that would be the next course of action should the leak persist. Dumb question-Does the fluid get collected in the can and then recycle back into the <acronym title="transmission">trans</acronym>/torque converter when the motor runs? Right now I'm thinking this my be my best bet considering all the other seals I've replaced to this point. Any suggestions on where and which one? Does it have a large enough volume to collect fluid after sitting for 5 months?

I am thinking it has to be the vent tube given the infrequency of the drainage (only does it when parked for a longer period of time) and the quantity of fluid. I've got a roasting pan under it as we speak. Once the draining starts it'll dump at least a couple quarts over the course of the offseason.

R.R.-Please let me know how your experiment goes.

Many thanks to all!

John
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TC Drainback

Only half of the fluid in a TC can drain back; once the level in it reaches the bottom of the hole in the hub, no more can leak out.
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... Exactly... If you wanted to get the last bit of fluid out at that point, you'd have to roll the converter & get the drain plug
to the bottom...

My plan with the tube extension on he vent is not to put a catch can. Since the fluid in the cooler & torque converter are the high spots, without a working check valve, the fluid will always want to equalize in level. The vent tube is NOT the highest spot, so ya, you'll find leaks at the tail, cooler fittings, fill tube, any other low spot that is seeing more liquid level (pressure) from higher than usual fluid levels. By extending the vent tube up to where the master cylinder is, the fluid can never make it's way that high, so no catch can is necessary. When you run the car & the fluid levels return to normal as the high spots fill back up, the level in the vent tube should get drawn back down. That's the theory at least. I will post how it goes - nothing more frustrating than following a thread & never hear what finally worked/didn't work. If the trans is in-car & you want to see if you have fluid coming out the vent tube, it's easier to see if you pull off the Neutral safety switch. The way the tube is situated, it drips onto the pan rail & runs around so it's hard to locate otherwise. If you have a piece of tubing to slip over, you can extend it into a pail & then there will be no guesswork if that tube is the source. You need to pull the switch off to extend the tube anyway.

R.R.
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... Update...

I replaced all the parts that were leak spots as previously posted. I put everything back together & filled the trans back up with proper 'TYPE F' ATF. I ran it in neutral, got it up to temperature, cycled through the gears, checked the level... rinse, lather, repeat... for about an hour 'til I got the level right/stable. Shut'er down & waited... It's been 2 weeks... no leaks anywhere, no fluid in the vent tube extension. (I had filled six 1-quart bottles with what came out of the trans, when I pulled the pan off/while I was waiting for parts.) SO - only a couple quarts were left in the lower half of the converter. I'm thinking maybe the trans had the wrong type of fluid in it from the P.O.... Why? because last year I had a problem with my power steering leaking like a sieve too - especially once the fluid got hot. Even the return lines would leak at the gear clamp connections (low pressure!) The system had clear (non-ATF) fluid in it & it needs ATF... The P.S. pump was pooched & screamed like a banshee! Once I flushed-out the system & replaced the pump/re-filled with proper ATF, no more leaks! ... Back to the trans... I was fully expecting to see SOME fluid in my overflow tube extension after a few days - but still dry after 2 weeks. We haven't hit really cold temps yet (that's when it was real bad last year), but even so - after a few days - no matter what, there would always be some. This leads me to believe that the trans also had the wrong fluid in it & because it did not have the right properties, it was able to leak by the anti-drain back check valve. Now I'm wishing I woulda got that last 2 quarts out. At this point it's not leaking, so I'm happy. At the very least; it's a plausible theory that fits the facts...

R.R.

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