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Early sign of blown head gasket?


JackFletcher
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Background: I got my Pathy back in July of 2018 and it had about 103k miles on it. Originally it was leaking oil and i had that repaired by a mechanic I believe it was the oil cooler seals. The mechanic did an oil change then.

 

Yesterday I did my first oil change on the pathy at 106k miles. I didn’t want to mess around because I wasn’t sure what oil he used and I like to stay on my own intervals. So as I was changing the oil I took off the oil cap and I noticed a lot of reddish brown powder on the inside of the oil cap. This concerned me cause I know brown sludge means you’ve got a blown head gasket. I checked the radiator and it’s green and full and the reservoir isn’t low. I cleaned the cap with some brake cleaner and then went on with the change. I didn’t think to take pictures of the cap when it was at its worst before I cleaned it but I went to take some pics today of what had already started to build back up after me cleaning it. d3cf2db507c929e12e2a402126afcc77.jpg21a701138f709e1fc6bdb746dae3706c.jpg

 

The first pic is the cap and the second is the hole you put the oil in for a lack of a better word lol

 

Prior to me cleaning it the cap was almost completely brown on the inside but there was no sludge it was just that brown dust. Let me know what you guys think is going on. I should also note that the truck is running normal. I am just learning about cars as this is my first one so any guidance would be appreciated. I could be just overreacting lmao

 

 

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Don’t be alarmed, I did the same thing recently after rebuilding my engine and having a misfire issue. I pulled off the oil cap, and there was some sort of residue there, and I freaked out, assuming the worst.

In this case, what you’re seeing looks normal, at least from what I’ve seen.

However, lets not just shrug it off immediately.

 

What you’re likely seeing is the results of colder outside temperatures (assuming its winter where you are currently), short driving trips, or potentially a clogged PCV system (unlikely, but possible).

 

You see, when your engine warms up, it dumps a lot of fuel to help it warm up faster and get the catalytic converters warmed up so emissions and oxygen sensors play nice. A warm engine is more efficient, and your crankshaft bearings take less of a beating at higher temperatures.

 

While everything’s expanding due to heat, and oil is being whisked around, that excess fuel dumped into the cylinder can blow by the piston rings a little under idle/warming conditions. This is called blowby. The result is a small amount of gasoline mixing in with your oil. Conveniently, modern engines have a preventative measure for any damage that would cause, called the PCV (positive crankcase ventilation) valve system, which allows the pressure from the blowby, and the evaporating gasses from the fuel, to be safely vented into the intake to be burned off.

 

The oil cap, being at the top of the engine, and being made of plastic, is typically cooler than the rest of the engine. Residual gasses from the oil and fuel blowby can condense on the oil cap, leaving behind a range of strange debris or colors (sometimes yellow, tan, or dark brown). This is completely normal, and should only really raise a flag if there is a lot of it, your valve covers and other sealed surfaces seem to be seeping oil, or you have poor engine performance/idle (this would indicate a possible faulty PCV valve). This sort of thing tends to pop up the most during colder weather, and especially in winter climates, due to short trip driving or letting the engine idle up to temperature for too long.

 

So now that you have an idea of what the issue COULD be, it’s a lot less alarming. I really wouldn’t worry, but lets check a couple things!

 

 

 

First of all, you said you changed the oil. By dumping the oil or checking the dipstick, a very alarming and fast indication of a blown head gasket would be a milkshake-like oil substance. Usually, it looks a lot stranger than brown sludge, so cross that off your list. Do a quick google search on blown head gasket oil, and you’ll see what I mean. It doesn’t take much for the coolant and oil to mix to make the nasty stuff, and you’d definitely notice it if it were severe enough.

You also mentioned checking the radiator. While it’s less likely for the oil to make its way into the cooling system with a head gasket issue, it’s still possible, of course. Typically, the exhaust gasses are what make their way into the coolant, and while it can be hard to detect, there are texting kits for about $40 at local auto parts stores that allow you to test and see if you have exhaust gasses in your cooling system. They’re pretty simple to use, but you might only want to for peace of mind if you’re still not convinced.

 

If you want to put some time into diagnostics further, pull your spark plugs and look at the color of the ceramic tips around the electrode. There are plenty of images online that can tell you how to “read” your spark plugs to know if you’re burning oil, running rich, lean, or have a head gasket problem. If it’s a small leak, it may not be noticeable.

While you’re at it, rent a compression tester, check cylinder compression, and perform a leakdown test on the cylinders. This can be one of the fastest ways to indicate a failure of some sort, whether it’s a compression issue, valve issue, or head gasket.

 

You could also rent a cooling system pressure tester. If you have a borescope, this can be really useful, but not everyone has one. You can perform a leakdown test according to the factory PSI specs of the vehicle. Typically, if it holds the indicated pressure (typically 13 PSI for older pathfinders), for 5 minutes or more without dropping significantly, you’re fine. Take it with a grain of salt, because a rental kit may not be 100% accurate, and could leak down even if you don’t have a leak, but it’s usually very slow. Sometimes, if you’re lucky (and unlucky I guess), coolant will come out of the damaged part of the head gasket around the heads or block, indicating failure.

With a borescope, in short, you could look in each cylinder after a leakdown test to see if there is any coolant puddled up on the piston.

 

Finally, an old trick from one of my mechanic buddies:

Get a white piece of printer paper. Take the dipstick and wipe it off, dip it again for fresh oil, and put a good drop of it on the paper. Try and keep it as collected as possible and not splattered all over it. Let it sit until it soaks into the paper all of the way. It could be a while.

If there is any small residue from a head gasket failure, typically it’ll sit on top of the paper and not soak in. Otherwise, the oil should soak into the paper and have very little variances in color. Obviously this is no engineering test, but it’s another quick and easy one for peace of mind.

 

 

With all of this in mind, “brown sludge,” as you called it, could potentially be a different issue, sludge buildup. This comes with a range of other symptoms, however, and can be found various ways. If the previous owner took good care of her and did routine oil changes, cross that off your list. Regardless, throwing in a little Seafoam into the oil a few hundred miles before your next oil change can’t hurt, and could break up any potential sludge you do have (I usually drain about a quart of oil, dump a bottle of seafoam in, and run it like that for a day, changing the oil the next day).

 

Good luck! Let me know if you have any questions!

 

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Just as another bit of supporting evidence,
Here’s some pictures from when I rebuilt my engine.
The first picture is when I was taking it apart to clean it and replace the timing, the second is after. Look at the timing stuff and rear timing cover and you’ll notice loads of the dark brown dust/gunk. It was just oil residue that had been burned onto the aluminum over time. The engine was otherwise perfectly healthy. It’s a normal thing as engines get older, and this VQ was at 186,000 miles when I did this teardown. Now its bordering 200,000.

3415b61dea9fb631f08a67b7c8ad123d.jpg

2b67b4ea7b1312c5296f47eb036f3d82.jpg

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This information is great. I am very thankful for all that you wrote. Based on what you said, you have basically described my driving habits. The temperature is in the thirties and i drive 2-3 mile commutes to school early in the morning. I am very grateful for this piece of mind I was getting a little worried. I dont think I will escalate the situation because I think what you first said about the influx of oil being swooshed around and gasoline entering makes since considering my situation. Also seems a bit low mileage for a blown head gasket. I will keep you posted on any new information I gather. Thank you very much sir!


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I will keep you posted on any new information I gather. Thank you very much sir!



Of course! That’s what this community is here for. Hopefully it all goes well from here. Just check on it periodically, especially the dipstick, to see if anything changes. Depending on the engine model, Nissan makes some pretty robust engine designs, I really wouldn’t worry.

Glad I could help.
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Yeah I think it looks good haha

I do think the brown coating it from running non-synthetic oil though. Not a particularly bad thing but an effect of dino oil for sure. With my old engine I only used havoline 10w30 dino oil and my cap looked just like that but worse. Dry looking light brown coating that could be scraped off into a powder.

This is what a BHG looks like:
6b47ff6bb959f8926a47ceba7013ee03.jpg

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14 hours ago, onespiritbrain said:

Yeah I think it looks good haha

I do think the brown coating it from running non-synthetic oil though. Not a particularly bad thing but an effect of dino oil for sure. With my old engine I only used havoline 10w30 dino oil and my cap looked just like that but worse. Dry looking light brown coating that could be scraped off into a powder.

This is what a BHG looks like:

I agree I figured the mechanic just used conventional. I put in some valvoline full synthetic high mileage. 5w-30

 

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Amazes me that people are allowed to drive their car without knowing at least the basic differences between the caps under the hood...

I agree. Since I am in Highschool I have come to find out that basic knowledge about engines is something that 8/10 people don’t learn. Most people around here don’t even know how the check their oil...
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Amazes me that people are allowed to drive their car without knowing at least the basic differences between the caps under the hood...

 

At least it’s a somewhat self correcting problem

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  • 3 weeks later...
Almost all of  my driving is about 20-30 minutes in the car,  highway and freeway. I put in about a quart of conventional oil ever 1000 miles to keep it level.

Hmm I remember that shorter trips can cause that because of moisture... can’t remember why exactly, maybe someone else would be able to help. Although your rips don’t sound short, usually it’s with stopping and starting with around the town driving
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1 hour ago, joshrichard said:


Hmm I remember that shorter trips can cause that because of moisture... can’t remember why exactly, maybe someone else would be able to help. Although your rips don’t sound short, usually it’s with stopping and starting with around the town driving

Yeah that part of it was explained earlier in this thread. Seeing as I don’t take short trips and my residue is a lot closer to what a blown head gasket looks like, I’m kinda concerned

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