Oil leak - cam seal or cam gear

So as the title implies, I have an oil leak that seems to come from the front of each intake valve cover. I went ahead and used two new cam seals, cleaned and reseated the seals. Less than 100 miles and the oil is leaking from the same two spots again...

I wouldnt mind the oil loss, but the fact that the drops are going down my timing cover, on to my alternator and ac condenser, I would rather get this sured up sooner than later.

I checked my cams gears for play during my rebuild a few months back and I didnt notice any glaring but I've never held another (good/bad) cam gear for reference.

After my rebuild I turned the boost up to around 15-16psi (haltech everything plus e85) and blew out my dip stick and sprayed oil everywhere. This is when I learned of the pcv system and its limitations when increasing boost... This made me think although I seated the cam seals properly in the build, perhaps this excessive crankcase pressure managed to blow them out of place enough for a leak.

I modified the pcv system thinking it would alleviate the problem (plugged the 2 pipes on left exhaust cam, plugged the pcv valves, plugged the charge pipes, added two catch cans under each intake valve cover pipe). Since my dipstick isn't blowing out and my catch cans are basically empty, I figure it cant be pressure pushing the seals out. So, either twice I've improperly seated the both intake cam seals only (exhaust seals are fine on both sides) or there's something else going on here.

Here are some pictures I just took showing the leak coming out behind and under the crank pulley, also dripping onto the alternator as well as the ac and power steering line.

Thanks

 

did you torque each valve body down to fsm specs?

 

Yes, I torqued the intake covers to I think 3lbs and the exhaust covers to 5lbs using an AC Delco digital torque gauge. Thanks for the suggestion ADAMZX

Any other thoughts?

 

Here are a couple pics of the first time I reseated the cam seals. I never really could tell if the oil was coming from the seal or back of the intake sprocket

 

Could be the seals in the vtc sprockets themselfs. Not uncommon.

 

Did you use new rubber "washers" on the intake cover bolts? If so they've probably hardened and you'll need to retorque.

Alternatively the rubber gasket has hardened/shrunk a bit and you need to retorque.

We've had to do that with recently rebuilt engines.

 

Kickerzx, this is what I am leaning towards. I just was hoping to find a way to test that theory before sending $500 to BDE.

ID - I did not use new or old rubber washers. Instead I replaced those bolts with the dress-up bolts from Z-Spec Designs via Z1 motorsports.

Rob - I put a dab of sealant (permatex ultra copper) on the corners of the end caps. So, 2 dabs in the front of the head and 2 dabs in the back.

I really am leaning toward the cam gears being worn out. Is there any way of testing/verifying without a full timing belt pull?

Also, I've always been curious why Nissan chose to use a rubber gasket on the intake covers but liquid gasket on the exhaust side anyone have some knowledge on this side quest? Again, just curious.

 

Thanks Rob. The fsm is actually a little vague on this one (unless we have different versions). It is hard to tell I'd the sealant is meant to go inside with the cam seal (direct contact with the cam seal); or as I have been doing it, putting the sealant in the bottom corners on the outside of the cam seal cap (no contact with the cam seal). Check reference image below.



I did use loctite on the new valve cover bolts and checked them for tightness after the plenum pull (still firmly snug).

I suppose we wont really get an answer here until I strip it down and fondle the cam gears a bit

I appreciate all the input. It's good to know my thought process is on the same track as you guys. After all the comments on here, I just cant see how the seals would be leaking at this point. So by process of elimination, I am betting on cam gears.

Rob: I will likely wait a month or so before I start this project (once it gets cold enough to store for the winter). I live in Georgia, USA so I'm guessing that would be a bit far for shipping . I've always felt aus300zx had the most useful threads and discussions.

Thanks again everyone, I will setup a reminder for me to come revive this thread in February once I have the results and repairs.

 

You could use a small mirror to look behind the VTCs before removing the timing belt to see if it appears oil is radiating outward on the back of the VTCs. A good way to check VTCs when they're removed is to use a rubber glove to grip the seal surface and see if you can spin it independent of the VTC body... if it spins, it's bad for certain, but no spin does not necessarily mean it's good.

I know of an instance where excess RTV plugged the small drain holes behind the cam seals which caused an external leak. You would need to remove the seals and poke something through the holes to verify they are clear.

 

Thanks LitlElvis, I havent heard of the clogged drain hole theory. I feel like I would have noticed if they were clogged, but I will make a note to specifically check that out this time.

 

I know the dress up bolts are more for show than durability, but they look so good with candy powder coated valve covers

 

You have done a great job and by the looks of it spent a fair amount of cash. Another $500 for some BDE camgears in my opinion would be money well spent. Its no fun pulling camgears with engine in car, just do it once. stop covering you engine with oil plus you will get an improvement with the BDE camgears against your 25yr old ones. I've fitted two sets to engines that have had leaking camgears with good results

 

Ok guys and gals,

I went ahead in jumped into my cam gear investigation and repair and this is what I found.



It's obvious oil is coming out at the front of both intake cam gears. Is this a typical result/symptom of worn out cam gears?

O-rings still in place. All bolts torqued per fsm.

 

Also, I replaced those o rings this past spring during the rebuild (o rings only, no springs).

Just looking at the pattern where the oil is coming from looks like an o ring failure or something. I have removed and re-seated the new o rings 3 times while going in and out of my engine, but I didnt put a single mile on the car until afterwards. Perhaps it's as simple as buying new o rings and springs?

 

Also, it seems there is oil leaking behind the cam gears.

 

yup front seals leaking, got the same problem on my z as well. cant really fix it until my next 100k service which is a few years away so im just leaving it for now.

 

When camgears leak the oil leaks from the back of the camgear not that front O ring. Its very difficult to tell whether the oil is leaking from the cam seal or the camgear itself, especially when its been leaking for a while and oil has been thrown everywhere. Normally I replace cam seals with Viton seals as a matter of course (they stand the high temps better) then if oil leak still exists I replace the camgears. This has always worked for me.