Potential Head Gasket Leak ?

I'm new to the forum, but I've got an 05 4.0 V6 AWD 4runner SR5. Bought it used from a car lot last December with 143k on it. Frame is really nice compared to the other ones I viewed before purchasing this one. (I wool waxed the crap out of it upon purchasing) now have 163k on it. I love this car but recently I've had a solid check engine light appear more than once. With P0304. So under my limited mechanical abilities, I've replaced spark plugs, checked coil plugs and tested the injectors for resistance. My spark plug on cyl 4 was very dark on the electrode compared to the rest. Replaced all, reset my code. It came back. But now everything is reading proper, but still misfiring. My coolant has a slow leak, very slow. My engine doesn't shake or overheat either despite the code. I've watched live data on my scanner as my husband drove it, no misfire detected. I'm at a loss. But it has a pending misfire. It seems almost intermittent. Oil is clean, coolant looks clean, no white smoke from the tailpipe as far as I've seen. I have a feeling it's a weird pinhole in the head gasket due to the limited symptoms it has.

Fast forward, let my very much mechanically inclined father know what's up; he's going to leak down test Cylinder 4. I'm curious how many on this forum have had this issue considering it's a big one for the 03's - 05's. (insert eye roll- thanks Toyota) and could it just be my injector not spraying? What am in for doing this if this is the case? Should I buy OEM gaskets or aftermarket? Also would a valve cover gasket be the problem? It's leaking a bit. I snugged the bolts up.Being that I'm not a mechanic, I fear the worst. But it's not over heating so I'd like to assume the heads aren't warped and if it is the head, it seems straight forward. (I've replaced a head gasket on my previous car DOHC Honda)

Also, weird things happening with my linkage and or transmission range switch. Got a code for that; P0705. It feels difficult to shift it at the start. I sprayed it with penetrating oil, seemed to help but now it's back again. Kind of terrified this car will haunt me with mysterious issues lol

Any insight or thoughts is appreciated! Thx!

 

Welcome

 

1) i like the screen name
2) if its an 05, yes its likely that its the head gasket.

Since the head gasket was redesigned for the 2006 model, i would say that you likely would be ok with doing new gaskets
Whatever you do, dont put the head gasket repair goop in the radiator
Head gaskets are pretty expensive on these things because you gotta pull the whole world apart to get to them thanks to how Toyota assembles everything. You gotta pull the fan shroud, fan, fan clutch, water pump, thermostat housing, accessories off the front of the engine, to pull the oil pan, to get the timing cover off, to get the heads off. Also, everything off the top of the engine, intake, lower intake, valve covers, all the accessories and wiring harness that bolts to the valve covers ect.
If you have a small leak that you cant find and one spark plug getting gunky, the introduction of a tiny amount of coolant will cause the misfire which will gunk up the spark plug. Sounds like you have already narrowed the problem down, but the solution is a fair bit of work.

With the vehicle being 20 years old, do you tear down every single moving part on the front of the engine and just put it all back and hope for the best? Do you proactively replace everything because you are there already and significantly increase your price to fix? Water pump, thermostat, thermostat housing gasket, valve cover gaskets, head gaskets, PCV valve, timing cover gasket, timing chain tensioner, pullies, serpentine belt tensioner, fan clutch,..... do you need to replace the alternator or roll the dice.... They kinda suck to replace.... Now would be a great time to replace it. You see how quickly the $360 head gaskets and necessities can turn into $3,500 in parts if you replace everything you touch so you dont have to do it again?

 

Thank you for the through reply, Airdam.

Yeah, I've heard that goop is the stuff of nightmares. I'm staying far far away from that. If it needs fixed, I'd like to do my best to do a bulletproof repair. That being said, should I use only the OEM gaskets or is there an after market one that's a safe bet if it's a well known brand? So far I'm finding out Toyota is a sensitive brand to anything that isn't OE (but reliable) so I'm just curious what others have done and got the best results with. As far as narrowing it down, I hope I have. I'm preparing myself for the challenge. I have the leak down test planned for next weekend.

I'm definitely in the camp of inspecting every component and reassuring it's quality before putting everything back together especially timing chain and sprockets and replacing what it needs. I think given my mileage and the frame being in very good condition that it's worth it. So far I've been able to rely on this car up until this point. So I suppose I'd rather shell out the $$ now then regret not trying and ending up spending more in a replacement vehicle.

Also, would you happen to know where I can find a factory service manual for relatively cheap? All I've got is a Haynes manual but I'm concerned the information is too broad for the type of repair.

Thanks again!

 

Somebody will come along here in a bit and drop a link to the downloadable manual, i could find it but i'm kinda lazy and the search function while decent isnt the best and it takes a long time to find what i'm lookin for so maybe someone has it bookmarked and handy that will help us out.
The last one of these i did i think was last summer and the customer wanted to replace everything on the front of the engine INCLUDING the AC compressor and it was quite an expensive job, fan clutch, serpentine belt, water pump, tensioners, pulleys, thermostat, thermostat housing, gaskets, all OEM toyota. Most folks only do the bare minimum so i would say it depends on your budget. With 150,000 miles you are nowhere near wore out for a lot of the parts because that engine will regularly go 300,000+ on mostly all OEM parts. You lose a bunch of alternators on them due to oil change places allowing the oil filter to drain right into the alternator rather than putting a bottle under the catch basin. Other than that the engines are pretty freakin bulletproof as long as you keep the coolant changed every 75,000-100,000 miles. Dont leave the coolant in there forever and these engines last a long time.

 

Okay, awesome! I'm still learning the navigation on the forum myself, bit of a luddite when it comes to computers. But I'm learning anyhow. Hahah!

Wow, that's a huge undertaking, all those parts. But it's done thoroughly. My budget isn't bare minimum but if there's things that aren't necessary to replace at only 160k then even better. (Whatever looks suspect, I'll be trying to repair- I've already bought my valve cover gaskets before I learned my head gasket might be failing).
Noted! I'll definitely change out coolant at those intervals and clean up what I can as I dive into this.

Thanks again! I appreciate the insight.

 

https://partsouq.com/en/catalog/gen...b-srjsAAAAAH1TiVs=$&vid=0&cid=2&uid=338342&q=

 

@TitsorTires94!

You definitely want to use OEM head gaskets as well as any other major pieces/components.

Just an FYI any 4th Gen V6 built before 12/05 will have the old designed head gaskets that can possibly fail, (this will include early 2006 models) any built after that date has the new designed head gaskets, Toyota only sells the new designed head gaskets now.

For your and anyone else's FYI in the future the T4R build date can be found on the VIN sticker on the driver's door jamb.

You can possibly find videos on Youtube that may cover doing the head gaskets, I know there's a good thorough one for 3rd Gens on Youtube, I'll check to see if the guy has one for the 4th Gens, if I find it or any others that look good I'll post links in this topic.


Edit: I only found one deceit video, this is in a Tundra but the same engine.

https://youtu.be/pIbeoMpGxEc?si=sIOz800DYykLU64k

 

Just wanted to add this for any new DIYers doing any work on their vehicles.

I would advise you to take a lot of photos and or videos before you remove anything, step by step, so you can refer to them upon reassembly, also use zip locks to put bolts, nuts and small parts in for each assembly/part removed and label it with a sharpie, use painter's tape and a sharpie to label wires, vacuum lines, etc.

Organise the baggies on a work table in the order they were removed so you can just reverse the order upon reassembly.

The best restorations shops out there follows this methold religiously to make sure they get everything correct.

Edit:Also when installing the heads use painter's tape to seal off the intake and exhaust ports so nothing can fall into them prior to installing the intake manifold, a small nut, bolt or washer can destroy engine upon trying to start it if accidently dropped into one of the ports unnoticed.

 

@AuSeeker

Thank you so much! I really appreciate this. This forum is awesome.
OEM gaskets it shall be! I will take lots of pictures as I go through each step and thankfully I will have some trusty help from my Dad who's familiar with engine work. With the help of you guys on this forum and him, it seems a challenging but practical task. I'll be learning so much.

You have answered my question that I was going to propose next about the gaskets being sold as the updated versions. Thanks a million. As for my build date, if I remember correctly mine was in May. I'll have to look in my jamb and check.

I hope this thread helps whoever else might stumble upon the same issues.

@Airdam, sorry to blow your notifications up, (I just figured out how to tag specific people) but thank you again! Very much appreciate you and your info.

Well once I've got my issue confirmed and fixed, I'll likely post an update on how it went.

 

Please do update this topic good or bad as you go along and when you finish, also some photos would be nice, it will more than likely add good info to help others in the future, also everyone here loves to hear updates!

 

Update - I have confirmed my issue being the head gasket. We confirmed it by doing a leak down test and used the camera to look inside of the suspected cylinder. Good news is I believe I caught it early enough before any severe damage could occur and my dad and I are working on a game plan to get it fixed. Will update again as I repair it!