Oil leak, oil in coolant reservoir; opinions needed!
 

Fellas, I've made several threads on this forum in the past with questions regarding certain parts to buy; now I'm here with my first engine related issue, and it seems to be a big one. Here goes. 2005 Infiniti G35x, 92,440 miles.

To start off, I replaced both valve covers two months ago with some cheap ones from rock auto. Since then I have taken two highway road trips, and I've noticed that although my G burns hardly any oil in the city, it does go down about a half inch on the dipstick on a 600 km road trip. However, I never noticed any oil under my vehicle.

Two weeks ago before I rebuilt my entire front suspension, I decided to get under the car and have one last look in case there was anything I was missing. I found oil dripping down several components on the drivers side! The orginal spot that I found loose oil was on the AC condenser, exactly like the first post in this thread https://g35driver.com/forums/g35-sed...an-2005-a.html (OP never said what the problem was, I sent him a PM) It was hard to tell where the leak originated, so I removed my intake and saw the exhaust heat shield was covered in burnt oil and it had been running down. It seemed to go from the rear to the front of the drivers side cylinder bank along the heat shield, and it SEEMED to be coming from the drivers side valve cover. No big deal, I'll just re do the valve cover gasket. Well I replaced the gasket and used more RTV than last time, and everything went smooth. Repaired the rear left caliper as it was sticking, replaced the rear pads and rotors, bled my brakes, and then I was done. I moved to a different province yesterday as I start my new job in six days.

When I got to my location I decided to have a look under the engine to see if the gasket held up. Not a single drop along the shiny part of the camshaft bracket next to the valve cover and at the top; this made me happy. But the exhaust heat shield almost looked moist with oil again. I looked under my car and I see MORE OIL DRIPPING! Even more than before, in fact. Turns out it was never the VC gasket in the first place.

I wanted to make ABSOLUTE sure it was in fact oil that was dripping. My brake fluid reservoir was full, power steering fluid hadn't moved a hair since I flushed the system. I checked my coolant and... before the road trip it was a lime green color and right at the max line. Now, it was about an inch and a half above the max line, and a dark green, non see-through color. My heart sank as I knew I may have a blown head gasket. The car stayed at normal operating temperature the whole trip, and no smoke came out of the exhaust. I needed to clear my head so I watched the raptors/warriors game and decided to look at it in the morning.

This morning I had a look, and the coolant in the reservoir was about an inch above the max line as the fluid was now cold, but still a dark green color. However, I'd like to point out that it is NOT a milky, chocolate type looking fluid as I've seen in several posts. It more so looks like old coolant that hasnt been changed in years, although I flushed the cooling system only 30,000 km ago and right before my 500 km road trip, it still looked perfect. I opened the radiator cap, and the coolant looked fine, although there was definitely some oil floating on top. Lastly, I checked my oil dipstick several times, and the oil level was damn near exactly where it was before I left! Also, the oil looked perfect. No contamination, and just as clean as it always looks. WTF!?

Went to part source and rented a compression tester, the following are the pressures in my cylinders with 3 tests per cylinder; the number stated being the average of three tests.

Cylinder 1- 204 psi
Cylinder 2- 185 psi
Cylinder 3- 203 psi
Cylinder 4- 194 psi
Cylinder 5- 194 psi
Cylinder 6- 186 psi

I'm aware the differential limit is 15 psi between two cylinders, and I am at 19, however the normal operating pressure is 185 psi, which is the lowest compression I found in cylinder 2. I am unable to do a leak down test as my car is in the underground parkade and I don't own a compressor. An important thing to note is when I warmed up my car before doing the compression test, the exhaust smelt awful, almost like ammonia; possibly this is what burning coolant smells like?

So... I have a small oil leak that is NOT coming from the valve covers, but is coming from the drivers side (almost looks like its coming from one of the three tubes in front of the exhaust heat shield, the bracket by the AC condenser where the water bypass hose connects). I have oil that is leaking into my coolant very slightly, but no coolant in my oil, AND, the oil is also leaking from somewhere on the drivers side of the vehicle. I will try and take good pictures with an inspection mirror when I get a jack handy; unfortunately, all of my tools, jack, and jack stands are back home in Saskatchewan. I know it is not due to the oil dipstick not being inserted all the way.

Please help G35 community. I have put so much effort into getting my car running well so that I can have a reliable vehicle for work, and honestly that's exactly what it is. I've experienced the same wheel bearing, compression rods, blah blah problems that all of us have, but this is my first ever engine related issue and I'm afraid it could be a fatal one.

Thanks in advance.

First off the limit is not 15psi, it's 10% (so in this case 210x10%=21psi) so somewhere around 21psi on this engine. You're pretty much AT the limit but I've seen engines like that run for a VERY long time.

The next step is to drain the coolant into a very CLEAN container and inspect for oil. It will rise to the top and will be very obvious.

Drain the coolant reservoir separately, just unbolt the single 10mm bolt and lift it straight up.

The "ammonia smell" is more concerning to me though, that usually means something wrong with the catalytic converters, is it more of a "rotten egg smell" because that is a definite sign of a failing cat. Either replace with another set of cats or install test pipes.

EM-101 of the 2005 FSM states the differential limit between cylinders is 15 psi; regardless, the 4 extra psi I am over is not a concern to me. What IS a concern to me is I did a compression test a couple months ago, and cylinders 1,3,5 have not changed, but cylinders 2 and 6 have both dropped about 7 psi.

Drained my coolant from the radiator and reservoir... turns out, the lower half of my reservoir is so dark and grimy from the previous owner not cleaning it out frequently, that when I was looking in my underground parkade at the reservoir, what I thought was sludgy coolant with oil in it was actually just coolant I couldn't see through, with some particulates floating around. I'm still doing a coolant flush for my peace of mind.

So I still have an oil leak from two places on the drivers side that is most prominent after long highway drives, but the head gasket crisis has been averted. I'm going to wash out my engine bay and take out the intake, clean as much of the old oil residue off the engine from every single place I can reach. Then I'll let it run for a while and get in there with my inspection mirror.

That's good to hear it wasn't oil in the coolant. We always advocate when buying a used car to replace all fluids so the new owner knows exactly what's in there and when it was done. Not too expensive if you can DIY it but no matter how it's done the peace of mind is priceless...

Agreed, and coolant was one of the first things I did. Pretty sure you chimed in over a year ago on how to burp the system, Blue Dream.

Here is the coolant reservoir, after rinsing it out with water several times. Even with brand new coolant poured in it, the fluid in the reservoir looks like **** with no light being able to penetrate the dirty plastic.

https://cimg4.ibsrv.net/gimg/g35driv...55d8aa0890.jpg


Is anyone able to chime in on common oil leak locations on this engine, before I get in there like Sherlock? I'm not having an oil cooler seal problem, and I've already looked into the camshaft position sensor.

If you get oil in the rad... it's coming from the trans cooler :/. Autos have the oil trans cooler in the factory radiator.

Staining in the coolant reservoir isn't something I'd be concerned with tbh, unless it was a show car but you would be using an aluminum one and not OEM plastic if that was the case.