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Thread: Rear main seal replacement 03 Cobra

  1. #1
    Will Work For Car Parts Terminated's Avatar
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    Rear main seal replacement 03 Cobra

    So towards the beginning of fall I noticed what appeared to be a leaking rear main seal (oil buildup between the block and the trans plate), so I parked the car figuring I will work on it in the spring.

    I plan on doing this myself and putting a new TOB in while I'm there (squeaky until you put light pressure on clutch).

    My question for you 03-04 owners is, is this a common thing to happen just with time? Or are there other possible factors that may lead to this failure? I drive my car very lightly given what it is, and I find it hard to believe that after 8 years and 66k miles that it would just randomly start leaking.

    Also, is there anything else I should check for, or any recommended seal to use? I've read there are a couple different kinds, but just want to get some opinions. Sorry if this post seems to be overkill, I just like to know about my car and try to prepare for what I may expect beforehand.

    Thanks!

    Dan
    Dan -- 2003 Cobra DSG Coupe #6009

    If it looks good, you'll see it. If it sounds good, you'll hear it. If it's marketed right, you'll buy it. But if it's real, you'll feel it. IG: @donuttrump


  2. #2
    Bullitt Rowleyxlt619's Avatar
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    I have a 03 GT and had both rear mains replaced twice and one front crank seal at around 27,xxx miles back in 2008. Front crank seal was due to using BBK underdrive pulleys and the rear main i couldnt tell ya the actual cause other then when they replaced it the first time with the front crank seal. i parked it for the winter and when I got it back out in the spring of 09 it started leaking again so i took it back to the dealership and they put another rear main in. I did some research the week it was getting the second rear main in and from what people have told me was to replace the pcv valve... so i did and have had no problems with the car since...

    for me with the rear main seals. was ok what caused it to blow out in the first place with that many miles and NOT being a common problem. two was the second time they replaced it with may 10 miles on it from the time that i picked it up from the dealership that fall to park it for the winter, that maybe they installed it wrong? i couldnt tell ya... other then people telling me that maybe the pcv valve had a problem not venting and building crank case pressure and blowing the seals out... other then i got it replaced with the rear main seal and like i said i have no problems since 09 with the car.

    Im not sure if this info would help ya but i figured id share it with ya that i've already went down this road...
    2003 Ford Mustang GT
    AMAZON GREEN METALLIC, 4.6L, 5spd

    Best quater mile time-12.96 @ 103.45 (4/6/08)
    Best 60' time- 1.71 (4/6/08)

    1993 Ford Mustang GT
    93 Cobra Teal Met. 5.0, 5spd

  3. #3
    Will Work For Car Parts Terminated's Avatar
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    Actually that helps out alot too. I had read about crankcase pressure being a possible cause, but it also seems like the lack of use could also cause it... I will also grab a PCV valve and throw it on since thats a cheap and quick repair.

    Thanks!
    Dan -- 2003 Cobra DSG Coupe #6009

    If it looks good, you'll see it. If it sounds good, you'll hear it. If it's marketed right, you'll buy it. But if it's real, you'll feel it. IG: @donuttrump


  4. #4
    No Traction due to Paxton PaxtonShelby's Avatar
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    Most Fords leak a little out of the rear main, but boosted cars even more so from what I've seen. The PCV swap is definitely a good idea.
    2014 GT Premium - Sterling Gray Metallic - MT82 - Track Pack - Glass Roof - Recaro seats - Spoiler delete
    12.76 @ 114.04 bone stock. Koni yellow coil-overs, BMR watts, LCA and LCA relo brackets, Borla S-type axle back.

    1966 Coupe - 331 stroker - Bullet custom roller cam - cam and motor installed and dyno tuned by Rodeheavers Hot Rod - Astro A5 - McLeod RXT - 486 to the wheels - more fun than my little tires can handle

    1966 Oldsmobile Toronado - currently NOT on jackstands

  5. #5
    Will Work For Car Parts Terminated's Avatar
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    Quote Originally Posted by PaxtonShelby View Post
    Most Fords leak a little out of the rear main, but boosted cars even more so from what I've seen. The PCV swap is definitely a good idea.
    Yeah I've heard that too. Never noticed it on first oil change, but I did when I was under the car cleaning the exhaust. Oil level was spot on, and the bottom of the motor was just damp with it, but I'd rather nip it in the bud than keep driving like it is.
    Dan -- 2003 Cobra DSG Coupe #6009

    If it looks good, you'll see it. If it sounds good, you'll hear it. If it's marketed right, you'll buy it. But if it's real, you'll feel it. IG: @donuttrump


  6. #6
    Senior Member Dan B.'s Avatar
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    Wish I had a boosted car to worry about this type of oil leak!!
    Quote Originally Posted by John4cam View Post
    Ahh fuque
    1985 Ranger--2WD, basic bolt-ons and tires, 11.92 @ 111mph.

    1986 Ranger--2WD, 5.0/T5/8.8.

  7. #7
    Administrator burntire's Avatar
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    I had to change mine a few years ago. I think the car had about 12k miles on it when I did the change. It wasn't dripping on the ground, but I noticed the oil seep when I had the tranny out.
    2016 Mustang GT

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