[V8] Oil Seals

[DasWolfen at aol.com]

In a message dated 5/26/04 10:44:07 PM Eastern Daylight Time, 
roncav3 at comcast.net writes:

> Pretty new to the mailing list and I'm hoping that maybe some of you can 
> offer some words of advice.  My question is, can replacing the rear main seal 
> cause other engine oil seals to weaken and leak?

 Welcome to the list Ron. No replacing a rear main seal cannot cause other 
leaks...except in the rear main area if they didn't do it right.

> 
> I knew that my rear seal and valve cover gaskets were leaking.  I asked a 
> local garage (that was recommended) to fix the "oil leaks."  Well, I got my car 
> back after having the rear seal replaced (I did the valve cover gaskets) and 
> my car was still leaking oil.  The garage determined that it was now the 
> front seal leaking because replacing the rear seal caused "pressure to crack the 
> front seal."  Is this guy for real?  My problem is, I knew the rear seal and 
> valve cover gaskets were leaking when I brought it in, but didn't think to 
> look for any other leaks beyond that one.

  Your shop isn't familiar with the V8's crankcase ventilation system. The 
only way to pressurize the crankcase to the point of causing leaks is to pinch 
off or crimp the vent hose on the front of the engine....look for a temp sensor 
on the driver's side head you'll see a hose about 3/4" diameter in this area 
running from the throttlebody hat down under the intake...Pinch off this hose 
and you'll find every place a V8 can leak oil in short order....as I 
discovered on my own 1990 V8 several years ago.

 A more likely situation is that you have one or more of the numerous leaks 
possible from the front of a V8...in my experience the front main seal is the 
LEAST common. More likely is the Oil Pump drive seal...its beside the front 
main and lower on the engine, ie: closer to the surface of the oil in the sump. 
If the shop has done a good job cleaning everything in the front of the engine 
before attempting to diagnose the leak and they still say its from the the 
front main area my money would be on the oil pump drive seal. My experience is 
that I've never seen a front main leak with less than 200k miles on the engine 
and I've never seen a original oil pump drive seal that wasn't leaking by 100k. 
My theory is that under moderate braking the oil in the sump reaches the oil 
pump drive seal and allows it to leak that way.

 Other possibilities include your new valve cover gaskets. Its very easy to 
pinch one when installing. They can also fail to seal a small area at the joint 
of the cam bearing caps. The both oil pressure sensors are known to leak on 
occasion. Then there's the worst leak of all....the oil return area of the head 
gaskets...both sides at the lower corners.

 All that's assuming it's an oil leak in the first place. Hydraulic fluid can 
appear to be oil after its been on the bottom of a dirty engine. 14 year old 
hydraulic hoses fail regularly. The two most common leaks I see in this area 
is the crimp on the fluid supply hose..thats the large middle hose on the pump, 
if you can twist the crimp by hand its leaking, and the power stearing 
pressure hose...medium sized hose on the back of the pump. A p/s hose can be a real 
pain to diagnose if you're not familiar with the system because it rarely 
fails outright. The construction of the hose tends to dampen the leakage so it 
doesn't spray the way you might expect. It tends to slowly seep out of the 
insulating jacket except when holding the steering at full lock. 

 Good luck!
Keith