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Is this normal to leak?

Hi everyone,

My check engine light came on Monday night. Car was fine sunday, then Monday evening I went to turn it on and light came on. No issues as I had to make an apt to get my oil changed anyways. Had that done and a diagnostics done today and they said my secondary air pump (or pipe I really need to call back tomorrow as I was working while talking and my work requires all my focus) was cracked which set off the light. But that I also have a leak in my Transmission Harness (I was at the dealership so they quoted crazy numbers!). But I called my dad who is a mechanic (6 hours from me) and asked him to call Lordco (auto parts place in Canada) and get a quote as my cousin owns it and I get a large discount from them. He instead called my brother who fixes VWs to ask if this is typical as he had never heard of the harness itself leaking. the Advisor I talked to said the mechanic said “The transmission harness is leaking itself”. But my brother says it is very rare. I was told still drivable for now but get it done asap. But is this typical of a 2008 VW Rabbit? Anyone else had this issue? Costs of repairs? I know air pump/pipe is easy fix but still issue.

Thank you in advance!

There should be no “normal” leaks from anything on your car. 30 years ago most cars had typical leaks that most would consider “normal” but I digress. This kind of stuff happens on a 9 year old car. You didn’t say how many miles are on it but I’d guess about 100,000 or so.

Transmission harness is leaking? I looked online and found transmission harnesses for your car that clearly show a rubber O-ring seal on a connector and several wires off of it that should connect inside your transmission. So it could be the O-ring itself leaking or the oil could be traveling inside the wire insulation and leaking out.

Fairly simple part. The part, a used one I found was $99. New looks to be $225. Not sure how much labor to fix this nor what your definition of “crazy numbers” might be so I can’t comment. Maybe the harness can be loosened and just the O-ring replaced without opening up the transmission.

Hi thanks for the reply. My car has around 96,450 on it. I rarely drive, it is a 2008 but I bought it used in 2008 with 36,600 on it. They told me I need to “replace” the harness. But when I talked to my dad he doubted that, as most leaks are just from connectors and I would only need an O-ring as you said. The dealership (and yes I know they pull you) quoted me 1600 to have it replaced (that price includes service). I know the Harness can leak, but I have never heard of it leaking on its own but from a connector yes.

There’s an o-ring around the body of the connector. There’s also the molded in pins in the connector that must remain sealed. If it starts leaking around those, you need a new harness to eliminate the leaking. I’d suspect the O-ring first. Most shops will not attempt a partial repair by looking for a suitable O-ring like most DIYers would. Especially if the labor to access it is significant. They, and you, do not want to risk a repeat visit if it’s not successful…

Hi, I called and they said main harness insulation pins in the harness. He said 2 parts would need to be replaced on the harness. This is the invoice. That is circled is what he told me.

No experience w/VW automatic transmission harnesses, but if transmission fluid dribbles into the harness pin/socket connectors it will eventually cause the transmission not the shift correctly. You know this is going to happen on the coldest darkest, most miserable winter night of the year, and you’ll be stranded at least 50 miles from home at the time. So best to get the problem corrected now, on a warm, sunny late summer day, near home. One idea, you might could save a little $$ by using an inde mechanic rather than a dealership.

Why VW would rely on an electrical connector to contain transmission fluid, never heard of that before. Seems like the fluid containment design would be separate thing from the wiring harness design. Combining those two functions doesn’t seem like a necessary risk; but I presume there’s a reason they did it that way.

This is nothing new

For YEARS Benz had the exact same problem

The transmission pass-through connector would leak. Fluid would travel all the way to the control module . . .

It took SEVERAL revisions until they designed a connector which was fairly reliable

Replacing o-rings by themselves did NOT solve the problem

Just curious, what does that part do?

When I called them to ask then what the fluid level was in my transmission, the guy said he did not know as the mechanic did not take the cover off. On my VW I have a cover that is “hiding” the transmission. I also, at the same time as they did the diagnostics had them to my service (oil, filter and top up of fluids). In order to put more transmission fluid into my transmission he would have needed to take the cover off. SO not I am curious how they knew where the leak was if they did not take the cover off, and how they added transmission fluid. They will be getting another call back from me. I also checked under my car this evening and see no leaks but I part on the street and there is spots already on ground so I have placed cardboard under to see what is there.

Yes I will be getting repairs done at an indie shop 100% like I normally do! But to diagnose my car I always go to a authorized place as they (indie shops) often don’t know the amount of codes VW’s have. I only drive my car 2-3 times a week IF that. I live in a city that has public transportation reaching my house in a 75 KM radius. But I am cautious to drive my car with issues I know should be taken care of, like the transmission, I grew up in a shop to know that.

Here is the part I was referring to. It’s quite easy to replace. Just don’t attempt to do it with the fluid at operating temperatures. There is a fair chance you’ll distort the electrical conductor plate, and the parts will never mate up correctly.

There has to be a way for electrical signals to find their way into the transmission, where the solenoids, sensors, etc. are located. And there has to be a way to prevent fluid from leaking out

Here is a connector for a Ford 4R70W and/or 4R75W, a very popular transmission at one time. This one is MUCH more difficult to replace


I understand why that’s necessary, but couldn’t the electrical connector be located at the top of the transmission where there’s no fluid? Up near the vent? Wires from the top connector would then run internally, so they wouldn’t cause a leak.

I have yet to see what you described

Consider this . . . the valve body, solenoids, sensors, etc. are located just above the level of the pan. So logic would seem to dictate that the electrical connector will be located accordingly

In my opinion, it would take quite a bit of engineering to design a harness that runs the way you described

I understand what you are saying. It must be just the practical problem of insuring access to that connector without having to remove the transmissions first, and where the wiring has to go inside the transmission. A leaking electrical connector seems like a frustrating problem to have to deal with though. I’m glad that’s not on my list of problems.

The reality of the situation is that many/most automatic transmissions will have a connector similiar to the ones I showed you.

But in the vast majority of cases, there will be no leak(s), or there might be minor seepage. Percentage-wise, only a few will have leaks so bad, that drops are seen on the driveway

it’s like with technical service bulletins. Just because something might happen, doesn’t mean it will. In fact, the majority of owners will not have that specific problem

Hi, I placed cardboard under the front of my car for 3 days nothing, it is now placed in the middle of my car. When I called them on Friday he said it was a slow leak and one that would not show on the ground. I talked to my dad and he said it is a seep not a leak then. Not sure why they would tell me it is leaking if it is not fully a leak.

Well technically a seep is a leak, and as to why they would make it sound worse than it is. They want your money, after all there is a reason some refer to them as “stealerships”.

Of course they want the repair because they make money to pay the mechanics. But the main reason is the inspection showed fluid where there should be none. If they say " no big deal " and it really starts leaking a lot then everyone is upset.