Hey guys,

I have noticed a large amount of oil on the underside of my rig, and need some guidance on things I should look into.

My valve covers are leaking (have been since I bought the truck a month ago) so these are first on my list. Parts are on order and waiting delivery.

But I am concerned about the amount of oil here. After the VCG job, I will clean and monitor, but I wanted to get a headstart in possible further diagnosis in case that is not the cause. I noticed oil on the bottom of my skid, dripping onto the oil pan, and traveling all the way back the side of the block. In my experience, valve cover leaks are slow and small, not this amount of wetness. Is it possible that this could all be from the VCG?

I am slightly concerned so have parked the truck for now.

On my list is the oil cooler o-rings, and also the rear main seal. I am really hoping it is not the rear main!

I have taken some photos:
Leak - Album on Imgur

anyways, long-time lurker here so happy to be a part of this forum!

Hopefully just valve covers. They can leak a lot. The half-moons and cam-cover in the back leak. Use a new tube of Toyota FIPG. I did it twice.

The leaking valve covers are indeed able to cause all that (from the pictures I see that do load).
I would not over-worry the situation and just pull the skid and clean it up. Then BEFORE doing any further work, clean the rest up as best you can - engine cleaner in a can and a pressure washer. This will give you a fresh opportunity to find the actual leak(s) and you can proceed from there.
I have a '98, bought 2 years ago as a fixer-upper for my still-not-driving-age daughter. One of the last things on the list is valve cover gaskets & timing belt etc. this summer (2021). It leaks enough that on a 2 mile driver training / mail box run you can smell the oil burning off the exhaust. It's been this way since I bought it. However, that "much" is barely enough to affect the oil level. I think I've only added oil once.

Like others have said, it's very possible that it is your valve covers/half moons leaking that much. Fix that first, give it a thorough cleaning/degreasing and then reevaluate before fixing/replacing anything else. If it does leak again and it's difficult to pinpoint where it's coming from there is oil dye that you can add which will be visible with a UV light.

Boom, thank you all so far. I am glad I was on the right thought process as to getting this sorted. I had the VCG's on the backburner while I fixed a few other projects on the truck, but once I saw the oil seem to lose more and actually dampen the skid and all the underside of the pan, I am now prioritizing it.

I have new OEM VCGs, half moons, OEM FIPG, and all the spark plug seals etc on order. Fingers crossed I can fix this easily without too much further diagnosis.

The rear main seal is my only true worry, as I'd have to have a shop do that rather than DIY... so let's see.

As long as you have enough oil I don't think you need to park it until you do the vcg's.

Yo CBlock! Small world lol.
You know how I am... overly cautious. Only reason I wanted to park it, was I am not sure its the VCG's...but I'm sure it's fine. My BMW's leak oil at the valve covers all the time but it is never a large amount, usually slow small drips and seepage.

I haven't lost anywhere near enough to sway the reading on the dipstick, so far. But when the VCG's were leaking a weak ago, they weren't this bad. Once I saw a bunch of oil stain on the bottom of skid plate, I just wanted to make sure it wasn't something that could lead to a worse problem.

As far as I know, these really only leak from VCGs, half moons and cam plugs, RMS, or the front cam seals in the timing belt area.

1) hope its just your vc gaskets, betting it is, its just rust proofing the bottom of truck now.
2) Ive also seen the oil cooler leak and for me with my big hands its a pain in the arse, and if you do have to replace the o rings, replace the hoses too
3) A friend had a leaking taco, some yahoo shop did an oil change and the rubber seal had seperated from the old filter and stuck to the engine, and they just slapped on new filter, am totaly amazed it threaded on and sealed and did not leak more than it did. He does not take to anyplace for oil changes now, he does them. But it was obvious it was leaking at filter base. After not being able to tighten, we pulled it ( and they had really cranked it on hard), found the extra gasket, and replaced with a YDD3
4) Hope its not rear main seal

Glad to see you on this forum!!!

Here is a really detailed video from @mtbtim
3.4 L V6 5VZ-FE Toyota 4runner, Tacoma, Tundra Valve Cover Gasket Tutorial - YouTube

Thanks! I've watched it. I hope to tackle the job early next week.

If it's leaking from the back I would suspect either the halfmoons or the rear main seal. If it is the latter then you're usually better off just running thicker oil to slow the leak.

Well, hoping its not the RMS.

Welp. Valve covers are done, it was definitely leaking. But.... I peaked underneath today and I still found some fresh oil. Frustrated.

It’s definitely coming from the back of the motor somewhere. I found fresh drips near the steering rack, and it drips down to the backside of the oil pan.

Could this be a rear main? Kind of running out of things to check here.

Attached some photos:
Leaking - Album on Imgur