• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

84 m1008 cucv rear main leak after modified intake

J.Peart

Active Member
Messages
159
Reaction score
51
Location
Kelowna, bc, canada
My 84 started leaking real bad a few days back from what appears to be the rear main seal. It probably still has the original rope seal so this isn't too surprising. i will probably change it out this week, but i am wondering about my CDR.

the engine only has about 120k miles, doesn't seem to have any blow by, but i just installed a 6" filter element. i used 2 housings to make a single tall one to fit the 6" filter. I'm wondering if the reduced intake vacuum could affect the CDR performance? Or does the cdr care about vacuum at all?
 

J.Peart

Active Member
Messages
159
Reaction score
51
Location
Kelowna, bc, canada
yeah i found an old thread on one of the other sites that explains it. wasn't sure if it would be fine with just atmospheric pressure but looks like i need some vacuum. buddy has the truck right now but when he gets back im gonna put a vac gauge on dipstick. maybe my intake is too free flowing. may have to introduce some restriction or change it back.
 

Will L.

Well-Known Member
Messages
9,704
Reaction score
11,017
Location
Boulder City Nv
Either that or get a bit more elaborate for a touch more power/mpg and far less oil burned:

Keep the airfilter flowing nice and easy like we know is best. Loose the over 40 year old designed cdr for a catch can with vacuum being pulled by a modern electric vacuum pump. With any luck you might get negative actual vacuum in the crankcase. Have to do a bit of reading to find the peak desired vacuum but iirc its 10”.

The vacuum pump will eventually wear out but the fords seem to get over 200,000 miles from them so... yeah. Subtract the cost of replacing the expensive cdr in twice and that is paid for. Catch cans are simple enough on ebay or diy.
 

ak diesel driver

6.5 driver
Messages
14,498
Reaction score
6,012
Location
alaska
Might want to read this
I had to buy that fancy vacuum gauge because it won't even register on a regular vacuum gauge. The closer the CDR pipe is to the turbo the more vacuum it has available. Don't have to move it very far away from the stock location to change it.
 

J.Peart

Active Member
Messages
159
Reaction score
51
Location
Kelowna, bc, canada
I'm pretty sure the CDR failed. i put a gauge on the dipstick and it read nothing at idle or at ~2000 rpm. i even pretty well covered both intake openings on the air cleaner (to max out intake vacuum) and it still read nothing. even if the gauge isn't sensitive enough to read 1" wg, it should have read something when i did that.

ill try cleaning it up in the mean time, but i'm gonna try to get a NOS one. still gonna have to replace the rear main. the bottom of the truck is coated now. it lost about a quart today over about 140 miles. went from a drop or two when parked to this over the last 3 days.
 

ak diesel driver

6.5 driver
Messages
14,498
Reaction score
6,012
Location
alaska
I couldn't get a normal vacuum gauge to budge. CDRs rarely fail and it would fail in the open position. The CDR is designed to stay open until a high vacuum situation, high rpm and high boost. When it closes it would be forced back open by rising crankcase pressure, or boost/rpm lessening. It's main function is to help reduce the amount of oil sucked through the CDR during that high boost/rpm situation. The CDR stays wide open 99.9% of the time.
 

Will L.

Well-Known Member
Messages
9,704
Reaction score
11,017
Location
Boulder City Nv
Until you fix the rear main seal- none of it is going to work right unfortunately.

I meant to say above the long life from the ford electric pumps should net us about 50,000 miles if kept dry by the math I worked out on It before, but that was accounting for new engine.

Once you do, You can safely run up to 15” of vacuum before you see any ill effects. At 20” of vacuum it is said you shorten valve stem seal life by 5%, but more importantly wrist pin oiling issues can start on certain engines so not worth getting to that level imo. however most 250 hp engines see about a 40-45hp gain at the 15” range. The 7” was what the is turbo cdr. The n/a cdr will get 5” irrc. No power or efficiency gains ar realized until 11” for most engines. Cylinder pressure is the reciprocal in the equation. So compared to most race engines our should be compared to alcohol engines or gas with nitrous.

Another thing to consider is the 6.5 mechanical belt driven vacuum pump.
It is important to make sure none of the oil is getting through the oil can to the vacuum pumps however as the oil tends to plug pumps requiring periodic cleaning.

About $65-$95 (depends on preference)gets you a fancy race level adjustable vacuum release valve from jegs or summit. But they can be found in commercial applications for $20 range. Many racers use a dash mounted gauge to see vacuum. I haven’t priced them out lately.
 

J.Peart

Active Member
Messages
159
Reaction score
51
Location
Kelowna, bc, canada
i intend to replace the rear main seal. i'm not looking for a way around that, i just want to make sure the cdr is working so the new seal has the best chance of working.

appreciate the suggestions Will, but i'm not looking to do a mod like that at this time. just want to get the stock set up working the best it can. if it turns out i don't have enough intake vacuum, ill put the original housing back on. perhaps i will look at vacuum pump set up in the future though.
 
Top