Crank No Start, Coolant Dripping From Oil Pan

[AlekAuto]

Please for the love of God let someone know what's going on here
I just finished doing valve cover gaskets, getting new spark plugs, new ignition coils, new radiator, suspension rebuild, I really treated her right. I even turned the crankshaft by hand before trying to start it.
I go to start her up, she'll crank for a moment like she has a low battery, then suddenly start clicking. When I check the battery voltage, it's around 11.5v. I tried again with a battery that was around 12.5, and it cranks longer, but still goes into the clicking thing.
The fuel gauge drops to the minimum whenever I'm cranking, then goes back to a quarter tank. Mind you, that quarter tank is probably half a year old, and it wasn't very high quality gas to begin with.
All the lights flash as you'd expect from a dead battery, but once again, battery isn't dead.

My initial thoughts were either a security lockout, since I plugged the battery in with the key in the ignition, or the crankshaft position sensor, since I had a code for that and I had the replacement lying around but hadn't actually installed it yet.

When I crawled under to double check where the crankshaft position sensor is, because I had an existing code for that, I noticed there was something dripping from the oil pan. I thought "Oh, guess the valve covers weren't the only leak", but to my shock, it was coolant dripping from the oil pan, not oil.

I immediately grabbed a wrench and undid the oil pan bolt, only to find nice, clean oil. Which unfortunately doesn't ease my mind much, since the coolant is also completely clean and fresh looking, so that doesn't exactly sate the part of my brain that worries there's a layer of coolant just sitting on top of the oil in the pan. But why would that literally ever be the case? Every time I've seen oil and coolant separated in the oil pan, the coolant is the bottom layer.
Dipstick is just clean oil, too.

 

The car hasn't even actually started yet. How could cranking it for a couple minutes tops possibly dump coolant into the oil pan? Why would it be so clean and not milkshaked at all if the motor spun while it was cranking? Is it a cracked block, or is the coolant coming from somewhere else, like the heater core hoses or something, and it's just dripping in the scariest possible place?
This thing was completely fine when I parked it, I parked it over a wheel bearing and decided to give it the full treatment before putting it back in service. What could possibly be causing this problem?

 

I have my own list of troubleshooting steps I'm gonna go through.
I'm gonna have to bite the bullet and drain all that fresh oil out to see if there's a layer of coolant on top, or, y'know, if coolant settles to the bottom of the pan overnight.
If it's not the absolute disaster my brain won't stop circling around, then I'll install a new crankshaft position sensor and go grab some 91 non-ethanol gas to dilute the stale gas with. Disconnect the battery for a few minutes, make sure the truck is closed and locked up, then reconnect the battery and unlock it with the key to minimize the chance of a security lockout

After that, uhhhhh kind of out of ideas other than "Time to start tearing it apart and looking for anything that might be keeping it from starting".

Yes, I probably should have done those things before posting, but I've been working for like 12 straight hours just to get to the finish line and have a panic attack. I just spent my last like 4 paychecks on this thing and was really relying on it during a move. If it's the worst case scenario, I have absolutely no idea what I'm gonna do. So, if anyone has any ideas other than what's already been listed, reassurance that I'm on the right track, or ESPECIALLY if anyone knows where the hell that coolant could possibly be coming from, please let me know.

Thanks for reading my memoir. Here's some pics of the coolant dripping and the clean oil. Yes, I'm aware the oil pan should be replaced because of the rust, but I mean, c'mon, that's not gonna magically make coolant appear.

 

 

Edited July 10, 2025 by AlekAuto

[AlekAuto]

Update: I decided it'd be better not to have this looming over my head while I'm trying to sleep, so I undid the oil pan bolt and the oil was clean the whole way down. The oil pan is completely empty, with the bolt removed, and 5qts of the most lightly used oil ever sitting in a jug in my garage, and the coolant is still dripping from the oil pan the same way it was before. This is not the oil pan gasket leaking coolant that's somehow defying physics by sitting on top of the oil.
So, wherever this coolant is coming from, it doesn't seem to be the worst-case-scenario.
Tomorrow, I'm gonna try the other troubleshooting steps I mentioned; making sure it's not the security system, replacing the crankshaft position sensor, and putting a few gallons of 91 in it to dilute the fuel.
Once again, if anyone else has ideas, especially about where the hell this coolant is coming from (this seems like a mighty large leak if I can watch it drip in real-time like this), then that'd really make my day a whole lot easier. Thank you.

 

I love that you can tell my moods from these images lol

 

[Slartibartfast]

Never fun when it goes back together and still doesn't work.

 

I'm guessing you've got a cracked coolant line or a loose block drain or something up above the pan, and it's running down. I don't know the VQ, so I don't know what the most likely culprit would be, but I'd start the search with anything coolant-related that you've touched recently, that's above where you're seeing the drips. Clean/dry the area if you're having a hard time seeing what's new and what isn't. But if it's a steady drip, it should show itself pretty quick, unless it's right proper buried.

 

The no-start and clicking really does sound like the battery to me. If it's resting at 11.5, then it's right proper flat. Are you sure the other battery is good? A clapped battery can show good voltage, but fall on its face when loaded. Do you have a jumper pack, or another vehicle that you can jump it from?

 

While you're in there, make sure your terminals are tight and clean, and check that you didn't remove an engine ground and forget to put it back on.

[CamperDan]

On 7/10/2025 at 3:49 AM, AlekAuto said:

Please for the love of God let someone know what's going on here
I just finished doing valve cover gaskets, getting new spark plugs, new ignition coils, new radiator, suspension rebuild, I really treated her right. I even turned the crankshaft by hand before trying to start it.
I go to start her up, she'll crank for a moment like she has a low battery, then suddenly start clicking. When I check the battery voltage, it's around 11.5v. I tried again with a battery that was around 12.5, and it cranks longer, but still goes into the clicking thing.
The fuel gauge drops to the minimum whenever I'm cranking, then goes back to a quarter tank. Mind you, that quarter tank is probably half a year old, and it wasn't very high quality gas to begin with.
All the lights flash as you'd expect from a dead battery, but once again, battery isn't dead.

My initial thoughts were either a security lockout, since I plugged the battery in with the key in the ignition, or the crankshaft position sensor, since I had a code for that and I had the replacement lying around but hadn't actually installed it yet.

When I crawled under to double check where the crankshaft position sensor is, because I had an existing code for that, I noticed there was something dripping from the oil pan. I thought "Oh, guess the valve covers weren't the only leak", but to my shock, it was coolant dripping from the oil pan, not oil.

I immediately grabbed a wrench and undid the oil pan bolt, only to find nice, clean oil. Which unfortunately doesn't ease my mind much, since the coolant is also completely clean and fresh looking, so that doesn't exactly sate the part of my brain that worries there's a layer of coolant just sitting on top of the oil in the pan. But why would that literally ever be the case? Every time I've seen oil and coolant separated in the oil pan, the coolant is the bottom layer.
Dipstick is just clean oil, too.

 

The car hasn't even actually started yet. How could cranking it for a couple minutes tops possibly dump coolant into the oil pan? Why would it be so clean and not milkshaked at all if the motor spun while it was cranking? Is it a cracked block, or is the coolant coming from somewhere else, like the heater core hoses or something, and it's just dripping in the scariest possible place?
This thing was completely fine when I parked it, I parked it over a wheel bearing and decided to give it the full treatment before putting it back in service. What could possibly be causing this problem?

 

I have my own list of troubleshooting steps I'm gonna go through.
I'm gonna have to bite the bullet and drain all that fresh oil out to see if there's a layer of coolant on top, or, y'know, if coolant settles to the bottom of the pan overnight.
If it's not the absolute disaster my brain won't stop circling around, then I'll install a new crankshaft position sensor and go grab some 91 non-ethanol gas to dilute the stale gas with. Disconnect the battery for a few minutes, make sure the truck is closed and locked up, then reconnect the battery and unlock it with the key to minimize the chance of a security lockout

After that, uhhhhh kind of out of ideas other than "Time to start tearing it apart and looking for anything that might be keeping it from starting".

Yes, I probably should have done those things before posting, but I've been working for like 12 straight hours just to get to the finish line and have a panic attack. I just spent my last like 4 paychecks on this thing and was really relying on it during a move. If it's the worst case scenario, I have absolutely no idea what I'm gonna do. So, if anyone has any ideas other than what's already been listed, reassurance that I'm on the right track, or ESPECIALLY if anyone knows where the hell that coolant could possibly be coming from, please let me know.

Thanks for reading my memoir. Here's some pics of the coolant dripping and the clean oil. Yes, I'm aware the oil pan should be replaced because of the rust, but I mean, c'mon, that's not gonna magically make coolant appear.

 

 

@AlakAuto, based on what I know about the VQ35DE engine in your 2002 R50 Pathfinder, there are a few potential sources for your coolant leak. One possibility is the water control valve, which is located under the lower intake plenum at the rear of the engine. My guess is that the rubber hose connected to it might have failed. I hope I’m wrong about that, as it can be quite a job to access. Regardless, I recommend starting with a coolant system pressure test. Another area to check is the rubber heater hoses that connect to your heater core on the passenger side firewall of the engine bay. If this were the issue, I think you would have noticed that leak by now. In my experience, when those heater hoses leak, it usually doesn’t run down the oil pan. Doing a pressure test may also help you pinpoint the leak.

 

Chris.

[AlekAuto]

Well, I got a lot of it figured out.
I checked the coolant lines that run along the back of the engine, nothing. I made sure the battery was charged, replaced the crankshaft position sensor, and put 5 gallons of 91 octane with some fuel system cleaner, then finally reconnected the battery with the car closed so I could unlock it with the key before entering to prevent the security lockout.
So, after all that, it fired RIGHT up like nothing was ever wrong.
However, it ran rough, and I noticed the valve covers I just installed were leaking. Badly. Like, not drip-drip leaking, but almost like they weren't sealing at all leaking. Smoke was coming out and everything.

 

I torque'd the valve covers to around 40in/ibs 'cause I couldn't get any actual information on what the real torque spec is (the manual says literally nothing on valve covers), and some guy online said it was "literally like 20in/ibs", and another guy said "no more than what you'd do with a screwdriver". Getting info on the torque spec of the valve cover bolts is hard enough, but getting information on the torque spec of SPECIFICALLY the aluminum ones from 2001 is nearly impossible.

I did find, however, that the Nissan Maxima, which doesn't share the same valve covers but is the only vehicle with the same valve cover bolts, does have the valve cover torque spec in the service manual. I wish they'd stop hiding these things.

It says to tighten the valve covers in two stages, once to 26in/ibs, and again to 82in/ibs. That's double what I torque'd it to. So, I'm gonna go in and tighten these down to the Maxima torque spec, see if that helps at all. Is it a bad idea/overkill to get these milled to make sure they're flat while I'm already taking everything off again?
I've already started taking the intake manifold off, so I'm gonna replace that thermostat while I'm down there. God knows I don't need more potential failure points.

 

Once I've finally finished all this, I'm gonna have stumbled my way into being the Nissan VQ Valve Cover Expert. My video on the subject is gonna include all the potential pitfalls one might fall into doing what would be a simple 30 minute job on any other engine, simply because I fell into every one of them.
If anyone has better information, I'd love to hear it. Thanks.

[AlekAuto]

A user on the NICO Club forum actually found the service manual for these valve covers, and it turns out, I was right when I said it was a good idea to use the Maxima torque spec in two steps technique, but I was wrong about the torque pattern. Here's the official torque pattern:

That's right, they hid it in the timing chain portion of the service manual! fskcin Nissan.

Even more in my defense than just the weird placement, there's a good chance there's a typo right there, since all other versions of these instructions tell you to torque it to 26in/ibs, and this tells you to torque it to 78in/ibs twice in a row. There's a chance it's just an extremely poorly written way of telling you to do the right one and then the left one, but I feel like this time Occam's razor says a typo is more likely.

Here's the lesson: Don't reuse valve cover bolts on the aluminum valve covers! The used ones have just enough corrosion on them to cause a bit of extra friction, which makes them reach the torque spec early compared to the new ones. I gave one side new bolts, reused the bolts from the donor Pathfinder for the aluminum valve covers on the other side, and guess what? The side with the new bolts is sealing great, and the side with the reused bolts isn't. This is especially apt, since the side that got the new bolts was actually the side that wasn't sitting entirely flat when I first installed it, so if all things were even, that'd be the side you'd expect to leak. The scientific method at work!
See? I'm not just a lunatic doing everything wrong on a valve cover job, I'm offering valuable information to future generations of R50 owners 

[Slartibartfast]

Figures they'd find a way to overcomplicate the valve covers, then screw up the documentation. Good work wading through it!