Engine/Transmission (1994 - 1998) 98 12V front motor oil leak

[IC Smoke]

My bud has a 98 12V that he just bought and it has a oil leak on the front of the motor, mainly towards the front of the motor. It leaks down onto the tie rods. It looks like it starts behind the fan pully... . Were both in the gray on where it starts and what its goign to take to fix it. 115xxx miles, pump has been rebuilt and valves have been adjusted at 100,000. auto trans/3:55 gears

 

[Joe G.]

That may be a failed KDP. If so, it's a bear to fix.



Look here: http://www.flex.net/~triplem/new/dowelpin.htm

 

[JGK]

Hose everything down good with engine degreaser and spray it off with water. Let it dry. Then fire it up and rev the engine a bit. Run it maybe 2 or 3 minutes at most. It will take a lot less if its the KDP. Shut it down and watch for oil.



If its a gasket leak behind the gear case (as mine was) its a bi*** to fix. If its the KDP, its just as bad except you get to buy a new gear case!



Welcome to the TDR!



-Jay

 

[Vaughn MacKenzie]

If the KDP failed and damaged the case bad enough for there to be a hole or opening, washing it down with degreaser and water probably wouldn't be a good idea.



Vaughn

 

[IC Smoke]

what is the KDP?

 

[JGK]

Well, Vaughn, I see your point, but I'm not suggesting squirting the case full of water! I doubt that hosing off the oil on the case and down under on the tie rod and oil pan will get much water in the oil through a breach caused by the KDP. Besides, after the fix, you'd want to do an oil change anyway.



But, IColeman, Vaughn has a point so take heed and if you decide to degrease the engine to find the leak, try not to squirt a lot of water, degreaser or whatever directly behind the fan hub on the engine block or the case. Go easy in that area.



And to answer your question, IColeman, the KDP is the Killer Dowel Pin and refers to a small hardened steel dowel pin inside the gear case on the front of the motor behind the fan. On some engines the pin works itself out inside the case, falls into a gear and gets carried around between the gear and the case. It causes the case to rupture and you get a major oil leak. That's the "killer" part. Nearly all 2nd gen. 12-valve motors (and a few early 24-valve ones) are suspect.



To fix it after it does its damage involves pulling the bumper, radiator, intercooler, fan, fan hub, case cover, injection pump, vacuum pump, cam (after removing rocker arms and push rods), and finally the case itself. But if it hasn't come out, there is an easy fix to keep it in place permanently by only removing the fan and fan hub. There is a day's worth of reading on this site on the KDP if you do a search.



Kits and jigs are available throught the members to stop it from coming out for only the cost of shipping the kit. The short of that process is to remove the fan and hub, drill the case using a jig, tap the new hole, and thread in a screw that blocks the pin from backing out. Another method is to remove the case cover and put a pear-shaped tab under an adjacent case bolt to block the pin.



-Jay

 

[IC Smoke]

Holy crap, that souns like quite the job! Its not a major leak but it tips off a red flag and is a little concerning to the both of us. He is going to pwr wash it down and i guess well go from there, are there any specific things to look for with a KDP problem?



Thanks again

Ian Coleman

 

[Forrest Nearing]

if it's a leaking case gasket, you can cheat and loosen the case, hose it down with carb cleaner and then brake cleaner to ensure the oil has been washed off, and then squirt gray RTV between the case and block.



if you end up having to pull the cam for whatever reason, please call Piers and get a cam! LOL!



Forrest

 

[JConley]

Mine leaked at the bottom of the gear drive case and dripped on the tie rods. It was a failed gasket, and it takes about 600 bucks in labor to fix. And it doesnt get any better. I tried everything until I gave up.

 

[Dave M]

I had a major oil leak also and in the same area you did ... all over the tie rods. I was adding 2 quarts every other week. I was not getting a major puddle under the truck... if you are then that's a bad sign. I suspected a cracked gear case due to the KDP. Turned out to be the front crank seal in the timing (gear) case, but the pin had worked out 1/8 inch and the case was okay. You won't see the cracked case till you remove the fan assembly because it is usually cracked under that because that's near the dowel pin which is where it usually cracks.



I got the tab kit from TST and it worked good. It cost $48 plus shipping and it came with the cummins front seal, the tab, a longer bolt, red loctite and RTV gasket sealer and the directions were very good... . I'm a novice do-it-yourselfer. It did not come with a front cover gasket which I got from Dodge ($35). I removed the radiator and fan but left the intercooler on since I have a big heavy front bumper I did not want to remove. I had to use a mirror to see some of the bolts in the gear case. Be careful while removing some of the gear case bolts. Don't ask me how I know but the bolt above the oil pump can easily fall behind the gears... twice... they are not easy to get out with the front bumper on, so take your time.



What these guys are telling you is right... it could be a cracked case... but you might get lucky... either way all that stuff has to come off. The bolts in the timing (gear) case also can come loose and they should be loctited (loctite comes in kit). That's the advantage of tabbing the pin ... you get to tighten the bolts and replace the front seal. The loose bolts can cause as much if not more damage than the pin falling out.



See my post "Novice fix loose Tow Mirror/Tabbed Killer dowel pin. . Help! Sludge in anti-freeze" for more help on doing front seal (the worst part of the job).



Good luck,

Dave