I just got my '99 FRC C5 about a month ago, with 48k miles on it. One of the first things I did was change the oil with 5w30 Mobil 1, like GM recommends.

When I had it on a lift to install Z06 mufflers, I noticed a lot of oil on the underbody. Its all around the bottom front of the motor, but not on the front of the crank pully itself, so I guess its got to be the front main seal (thats the only seal on the front of the motor right?).

Anyways, I guess the previous owner used some crap oil, so when I switched to synthetic it started leaking. I'm guessing the rear seal is probably leaking too. My question is, is there anything I can do other than change the seals? The front seal doesn't look too bad, I guess I have to pull the steering rack to get to the pulley. The rear seal looks like a bitch... If there is a good synthetic oil I can switch to that won't leak, I'd like to try that. Its leaking about 1 quart every 2 to 3 hours of driving.

I want to track the car (which will produce high oil temps), but I don't feel like pulling the clutch out just yet just to change a seal... Especially since I don't have the money for an aftermarket clutch right now.

Thanks for any help.

 

thats a pretty significant leak, you should deffinately replace your seals.

 

I don't know if I would have switched at that mileage. I switched at about 20k. Mobil 1, 5w30. No leaks, no problems, solid 40 pounds oil pressure for 14-15k more miles over the last 4 years.

 

C5s are only supposed to be run on Mobile 1 only, which is why I didn't think it would be a problem. Oh well.

 

The front seal can be swapped without removing the timing cover or water pump. If that's the only one showing oil, I'd stick with just swapping that one and leave the rear main seal alone.

Before you remove the pulley, inspect the seal's alignment around the crank pulley sealing surface. Look for a uniform gap between the outer lip of the seal and the pulley. If the previous owner had the cover off and didn't align it, or if he installed a new seal and oiled/greased the pulley, those are common causes of front seal leakage.

Plain old $5 seal puller claw from NAPA will remove the old seal easily. Installing can be done a variety of ways, the $40 J-tool available from Kent-Moore or whoever makes it a total breeze...plus, you can add a roller thrust bearing in place of the plastic seal installer cup and use it as a proper pulley installer.

 

oil leaks don't happen cause of oil used, happen from quality of the seal and duration of time in use.

 

Actually I thought different types of oil affected the seals differently? The other thing is that Synthetic oil is a better oil, and has different detergents or something. It will wash all the gunk away from the cracks and seals and cause leaking. There really is a use for that junk in the cracks and corners of the engine! Hmmm...I have always wondered why switching to synthetic on a high-mileage engine caused leaks, but switching early and running it for a long time doesn't....

 

I will never belive switching oils is going to affect seals cause the fact i've seen seals leak after 5 years anyway.

 

I've used Mobil 1 5w30 since I bought mine new in May of 98. Here is what happens to seals based on what kind of oil you use. Synthetics... of any brand or type, have special additives to keep seals from drying out over time. If you use early on, then the seal never has a chance to dry out. If you switch to Syn later on on seal life, your seals have dryed out somewhat (this does not mean the seal is bad, just that it's a little dry). When you add the Syn to this situation, the seal swells up and absorbs all those additives... and sometimes swells out of its seat or can open up a small hole or slit because of the swelling, hence leaks.

I have never had an oil leak in this car. 59K miles.

 

Could the timing chain cover have been removed and not aligned up with the oil pan correctly? Maybe no sealant applied to the bottom of the timing chain cover? If it isn't leaking from around the crank pulley, then it is probably leaking from the front of the oil pan. Just more things to check out.

 

I changed to M1 at 85k miles.. No oil leaks yet after almost 2k...

 

i doubt its from the oil but yes changing to a synthetic oil CAN cause leaks.. I work in the parts business and we have been told to instruct out customers to step up.. blend first then full.. some of the additives in synthetics are made to swell seals to prevent leaks but have actually been known to cause a few.. but this is the worst i have ever heard