Hello guys, I’m new here, I recently bought a 2013 G37 ipl from auction and it came with some issues, I’ve been having a misfire in cylinder 6 replaced all the coils and plugs and the misfire was still there, went ahead and dissembled the air intake manifold to check the fuel injectors and found this mix of coolant in my intake manifold, I suspect a head gasket leak or a pcv valve blow by, if it’s a head gasket a lot of mechanics told me to junk this engine and get a new one, because we suspect the previous owner already machined fhe top for a head gasket replacement and they claim that if we do it again the pressures inside are going to get messed up and the engine isn’t going to function right.

 

How certain are you that the engine was machined in the past?

The pictures that you show do show 2 funky substances in the manifold, some rusty oil/water/coolant in the runner and some gel that looks like it was gasket lubricant (its a gel lazy folks put on rubber gaskets to get them to seal)

The rusty substance appears to be on cyl 6 it's possible that this gel didnt do a good job with sealing the gasket itself.

I would suggest you clean all this up, replace the gasket and check again.


If the engine was machined then the heads might not sit well with the block, the timing covers and even VVEL assy.
But that's not to say that this issue aligns with the machine job, start with symptoms and work your way back.

A new engine will fix it for sure but if you can avoid it then so be it.

 

The thing I don’t get is how did the coolant get there? There’s nothing for it to leak around into, the gasket is meant to keep things air tight I assume, so did it travel up the air intake manifold? And from where?

 

Are you sure its coolant? Do you have any mods? If I where to guess it looks like you sucked water in through your intake track and it went into the first cylinder next to throttle bodys. You are looking at the upper manifold obviously, then you have the lower which the runners are a bit long then the head and then the gasket. That's a long way for coolant to travel up. I would suspect that your plugs would have some coolant as well if it is gasket issue. I feel like something that bad would cause your engine to overheat immediately.
As mentioned clean it up first. Top of your coolant and check the lvs to see if the coolant is going down. Or you can just pressure test it to be sure.

 

That gel is some funky stuff, since it was an auction car many times proper fixes are not entertained since, well the proper fix would yield more money than the auction.

Start doing proper inspections and clean anything you take out, the process of elimination is what needs to be followed with an issue like this one.

The reality is that these care are selling higher privately than through auction hence expect any non crashed V36 in auction to have some messed up issues.

You can visually tell something is getting into the intake track of #6, you should follow visual cues first then eliminate from what you end up finding.

 

runners are normally oily from the PCV system doing its thing. obviously this is more than oil. did the PCV hoses have similar contamination? have you changed/checked your oil?

 

I changed the coils and spark plugs, still didn’t go away, changes all the Lower and upper intake manifold’s gaskets still no luck. I’m getting these codes.

 

I'm sure you cleaned out the manifolds but I feel like I should still ask if you think it was coolant after all?
Not sure what all you have done but the coolant actually runs into the throttle bodys and back out to get them up to operating temp in colder climates.seems like a extremely longshot (pretty much impossible)but maybe you could have a fracture in the throttle body allowing coolant in from the top. Again doubt it but maybe still possible.

 

Hey I confirmed it was coolant, someone said the throttle bodies might be cracked it its a far fetch, but non the less, I will go ahead and give them a good clean again and delete the coolant lines going to them, I might as well delete the PCV just to make sure no oil is getting in there, so that's my bucket list, any thing else you guys think I should do? if it keeps misfiring I will replace the throttle bodies and see if that help.