Its dribbling ATF!.. why and the (temporary) fix

I haven't posted here in a couple of years (gosh, has it really been that long), not because I haven't been doing any wrenching (front lower ball joints and LCA bushing, trailing arm bushings, for example), but because the projects are significant enough that I'm sick and tired of car stuff by the time I'm finished and can't bring myself to post a writeup. However, this repair has stirred me out of my complancecy both because it didn't take too long, but also because it was a wakeup call to not be complacent and because there's a pretty decent chance it could go wrong with other's cars.. and they may not be as lucky as I was.

The Complacency

Hmm.. it seems to be leaking more oil than usual. Hmm.. it seems to be leaking a fair amount around the oil fill cap, and it's down a tad. One plus one equals two.. it couldn't possibly be leaking oil from someplace else. Well, its due for an oil change soon, so I might as well just top it off and find the leak when I'm under there changing the oil any day now. Repeat for a month. Stupid, stupid, stupid. If I think its leaking oil, I should figure out where. Its oil. Critical engine lubrication. And the oil cooler lines do go over time. If one pops, it can be catrostrophic for the engine (they don't like to run too well once they've pumped all their oil all over the ground). And at 3000RPM and 7bar, its gonna be dry before I can take my foot off the accellerator. Oh.. and my complancency didn't stop there either.. Noooo.. this time I went above and beyond and it could have cost me dearly.

A little while after that, I went to drive home one evening and noticed an oil puddle under the car. Did I peer under the car then? Heck no. I was running late for a meeting at my child's school and a school function (as long as I have to be there, the kill two birds with one stone strategy). Why is it major catastrophies always seem to happen to me on school function nights?

So what did I do? I started the car up and checked the gauges, especially the oil gauge. It was pegged like it should have been, so I drove off, figuring I'd drive home and park the car until I had time to find and fix the leak for real. A few blocks later and no oil pressure problems yet, but I checked the rear view mirror, just because I'm that extra paranoid (yet complacent.. an odd combination). And there, in the rear view mirror, I spotted a trail. A slight veer back and forth in my lane, and it is definately coming from my car.

So, that's when I finally checked. I pulled over, got out and leaned under the front of the car to see where the dribble was coming from. It was immediately obvious.. its dribbling so fast there's already little red puddle under the car. Diagnostic complete, its hemmoraging ATF and there's no way it'll make it home at that rate. Come to think of it, I'm not even sure it'll make it back to the lot at work where I can conveniently park it until I can trailer it home. See the nice ugly ATF trail it left all over the parking lot at work after I got it back there?

Diagnosis

I figured it was a simple case of a rubber transmission cooler line dripping.. or in this case dripping a lot. However, first step, analyze the problem to be sure I was right. Sure enough, the transmission cooler line is dripping, but not not at the the rubber line where I thought. It appears to be dripping in the middle of the metal line, right at the mounting bracket that secures it to the engine with an oil pan bolt. However, this is also the low point of the line, so maybe the ATF is leaking someplace else and just dripping off here. So I started the car and checked again.

Under pressure, you can see ATF is squirting out of the metal line. The paper towels are there to absorb any ATF running down the line. If it were leaking up higher and running down the line, it would soak the towels and I'd know. I expected a dribble off the bracket, but with the ATF actually squirting out of the line the diagnosts step is immediately over. The metal line is definately leaking and right there at the bracket.

I took the mounting bracket off and here's the damage. You can actually see the pinhole in the line but I circled it for extra visibility.

The Repair

Now that I know what and where the problem is, I can figure out a repair. First choice, replace the leaking line. That would be my choice, but would take weeks for me to get the part and make the repair. The only place I have to work on my car for that long is in my gravel and dirt driveway. Worse, its a low spot in the yard. Even worse, a puddle forms there in our rainy season. Which is nine months long. And should be starting any day now -- in fact, it looks like the first front should be moving through in in the next few days. I need to get this fixed, and it doesn't look like I have time to wait and replace the broken line. So what to do?

I decided to splice the line with some transmission cooler hose and hose clamps. First step, get access to the damaged section. I need to disconnect the rubber line so I can get a tubing cutter around the damaged section of the line. Two wrenches prevents any risk of the rubber line being twisted. The metal line needs a 17mm wrench, the nut on the rubber line needs something slightly bigger, probabyly an 18mm. The oil pan bolt also needs to come out to get the bracket off. That takes a 5mm allen wrench or bit.

Next step, cut out the damaged section with a mini tubing cutter as shown here. I could probably have used a hack saw, but I had this tool and it leaves a much nicer end on the cut line than I'd likely be able to manage with a hacksaw. I wanted to cut the damaged section of line out so I could figure out why it failed and so I was attaching any repair to line with a full round cross section of known wall strength. I also wanted to leave a gap in the metal line so the ends didn't rub together inside the transmission cooler hose I was going to make the splice with and damage it inside. This may be a temporary repair to get me through till summer when I can replace the entire metal line, but there's no sense doing a shoddy job of it. It might have to last longer than I intend.

Here's the pieces for the splice, including the piece of damaged line that I cut out (I won't be using that, but it helped me size the piece of cooler hose I would need. The hose clamps are not the ordinary garden variety ones, but rather what are called injection hose clamps. They have a solid band and were recommended to me so I didn't cut into the hose with the clamps. They weren't trivial to find, but were a good idea. There's also hose clamps for soft silicone hose which would have also worked. Injection clamps are what was available at my auto parts store. I intend to double up the clamps on the end of each hose for extra measure.

I measured the external diameter of the metal line at 0.461 inches so got transmission cooler hose with an inner diameter of 3/8th inch, slightly smaller than the metal line it will go over to ensure a tight fit. Make sure to use transmission cooler line, not ordinary fuel line or some other line. Transmission cooler line is designed to hold against the pressure and heat of the hot transmission fluid (i.e. hydraulic oil).

A drop of ATF on the outside of the metal line helped the new coooler hose slip onto it. Here's the completed splice. I put the oil pan bolt back in temporarily, reconnected the rubber cooler line, and started to engine to check for leaks. Success -- no leaks. However, as expected, without the mounting bracket, the whole splice shakes around a lot. It won't last very long that way.

I can't use the original mounting bracket because it won't fit over the splice. Besides, it was the cause of the whole problem (I'll get into that later). I could use some metal strapping and fashion a bracket similar to the old one that would fit around the splice. However, it will be squeezing around where I cut the damaged section of metal line out. I could relocate it to one side by attaching to a different oil pan bolt, but that that leaves one end of the metal line unsupported except by the new splice hose. Given how heavy that line is, the unsupported end will shake around and probably cause an early failure someplace else. What I need is something rigid that straddles the gap and secures to both ends of the metal, kind of like a splint. It also needs to securely attach to the engine -- the oil pan bolt that the old bracket attached to is convient.

Here's the bracket I came up with. I made it from some 0.064 inch sheet aluminium I had lying around. One hole along one edge for the oil pan bolt, with that edge beveled away from it for clearance of the nearby oil pan bolts and to keep it from rubbing on anything. Four holes on the other edge for some zip ties that go around the splice. Long enough so the zip ties fasten to the splice where there is metal line inside it. I'd like to use something better than zip ties, but I couldn't come up with anything I liked -- small wire might cut into the cooler hose and large wire might be too stiff for me to secure tightly enough around the splice. I'll just have to keep an eye on them and make sure they don't get brittle and break.

Here's the bracket mounted to the oil pan. Since the oil pan bolt can't be tightened very tight or it might warp the pan and cause the gasket to leak, a dab of blue threadlock should keep it from coming loose.

And here's the completed repair with the new mounting bracket securing the splice to the engine.






Root Cause Analysis

Now that the leak is repaied and the car drivable again, I wanted to understand why the line sprung a leak. Did I or the previous owner hit something? Did it flex there, eventually causing a fatigue break?

Here's a picture of the mounting bracket. The bracket is very soft metal and bent to be larger than it was when mounted on the car. I slipped a red index card into it for the picture so the hole in it can be clearly seen. Next to it is the damaged piece of line oriented as it was inside the bracket. The hole in the line matches almost perfectly with the hole in the bracket. But neither looks damaged -- the metal is just very thin and worn through. Noteworthy is that the metal bracket wore though exactly at an inward-protruding bend. The straight edge on the bracket along that failure is the dead giveaway. Look at the first picture, before I messed with the bracket -- it looks like part of the install procedure involved squeezing the end of the bracket with a pliers or something to tighten it around the cooler line. The inward bend that created on the bracket eventually wore through the rubber shim around the line and then, metal-on-metal, the bracket eventually wore through the metal of the line until it sprung a leak.

Why did I want to figure all this out? Because the metal transmission cooler line on the other side of the engine has a bracket that looks exactly the same. That line isn't leaking, but its probably only a matter of time. Maybe not, but now that I know what happened and why, I know exactly what to check for. I can choose to either let things go and see if the other line springs a leak, or do some preventative maintence. I could, for instance, replace the rubber shim in the other bracket. Or I could decide to replace both lines instead of just the broken one when I do that job. It also gives me damage to look out for if I decide to get used lines (like from a junkyard) for the replacement. My car only has 172 thousand miles on it, these lines could have been intalled at the factory and never touched until now. Those lines lasted a good while, but if I look for used lines, I may have to find some that were not installed at the factory. As long as I can afford it, I think I'll plan on replacing both lines with new ones so I don't have to worry about them again.

Cheers, and consider checking you car for a similar latent problem next time you're under it.