Help Dx 3.4L front engine oil leak - timing belt covers?

Hi all,

I’ve owned my new to me 2001 Xtra Cab for about two weeks now and it has unfortunately sprung a pretty serious leak in that time. I missed it initially because we’ve had so much snow and ice in UT, but I finally noticed a pretty large oil stain on my driveway yesterday. Got around to pulling the skid plates and everything towards the front of the truck was pretty much coated. Checked the dipstick level and it was below the probe; hope I haven’t been killing it over the past few days driving it with low oil. Anyways…

I’ve been doing a bit of research on the forum and it sounded like the main culprit for leaks coming from the front of the engine is the crankshaft seal. I dont think that is my problem here because the crankshaft pulley seems relatively dry and i believe the leak is coming from further up. There is a bit of oil on the corner of the timing belt cover near the sensor there. When the vehicle is running, I can watch oil drip on top of or near the AC compressor. I’m not well versed on engine anatomy, but it seems to me that the leak is coming from in or around the timing belt cover. However, all of the cases of leaky timing covers on here seem to be coming from the 4cyl with timing chain. Is it even possible for the timing 5FZFE timing cover gasket to leak this much? Or is there something behind it that could be leaking?

I stuck my hand behind the cover and touched some wet engine oil by the bottom left corner of the cover shown here. Not sure any of these other photos will be useful. Would greatly appreciate any ideas. Thanks!

 

Here are some decent photos of the pool beneath the leak source.

 

Possibly the front half moons, or a bad job applying FIPG, or camshaft seals:

Similar post: https://www.tacomaworld.com/threads/cam-seals-or-half-moons-leaking.461489/page-2#post-21033747 that has a good picture of the front of the engine.

 

Ah yes thanks that image is helpful. Left camshaft seal seems like a possible culprit. It looks like camshaft and crankshaft seals are usually replaced during a timing belt replacement. I’m going to need the timing belt done in the next 10k miles or so. Think it makes sense to just have all of that done at the same time to save on labor? I THINK I could theoretically do the seals myself, but I don’t think I’ll be able to do the timing belt, so if the labor is the same, seems like i might as well just have it all done by a shop and not take everything apart twice. Thoughts?

 

I'd wager it's the half moons before a camshaft seal. Often times the half moons are skipped in a valve cover gasket job. Given the amount of oil in your pictures, I'd guess the valve cover gaskets were changed out at some point. Given the cost of all that stuff, I know it's work I'd be taking on, but I also have the tools and time to do it. If the timing belt isn't a thing you'd do, then best to out source it I guess- It won't be cheap.

I'd also suggest cleaning your engine a bit. It will help with pin pointing the leaks. Spray some foaming engine cleaner in that area, and anywhere you can reach, wait a bit, and use a brush on a drill to agitate things, and thoroughly hose it off.



Whoever works on the truck will thank you.

 

The previous owner had the valve cover gaskets done in 02/2021 but it does seem possible that their mechanic might not have replaced the half moons. Is this (photo attached; red circle) what we’re talking about? Whether the leak is coming from the camshaft seals or the half moons, it looks like the labor to remove everything in the front of the engine will be comparable for replacing either of those. Does this labor overlap enough with the timing belt labor that it would be most efficient to have them all done at the same time, or are they distinct enough that its worth doing them separately? Like I said, I am comfortable doing this level of work, but I don’t have the time/tools to do a job as big as the timing belt. If there is considerable overlap, I guess I might as well just have a shop do them all together. Does that seem reasonable? Thanks!

 

Photo of half moons:

 

The half moon is what is circled in red. I replaced my valve cover gaskets and skipped the half moons (or was it the cam plugs?) in the rear and found that I had a decent leak there as well. So I opened it back up to redo that side (drivers). Ultimately, its probably easier and cheaper to open up the passenger side valve cover and redo those as well as add in a fresh valve cover gasket. It's relatively quick to get down to the valve cover in my opinion. Though I've never tackled the timing belt stuff. I've seen many people talk about leaking valve cover gaskets, half moons etc. Not so much the camshaft seal. Very likely the half moons were not touched when the fix was done in 2021. I'd definitely start there.

 

This is where I’ll start, then. Thanks for your help!

Think I should redo both sides or just press my luck and hope the right side holds? Huge bummer that this was all done less than 5k miles ago but ya gotta do what ya gotta do.

 

My .02: If you're going through the trouble to get down to that level of the motor, just do both sides. Would suck if in another 5k the other side decided it was time to leak.

The valve cover gaskets (and the half plugs, cam plugs, and spark plug tube gaskets) are a totally DIY'able with minimal special tools.

I also suggest doing the injectors (motorwest denso "upgrade") while you're there, and vacuum lines. There are just some vacuum lines you can only get to with all those parts off.

 

Make sure to get two gasket for the intake runner and a throttle body gasket if you decide to clean the TB. Also get new rubber impregnated washers for the valve cover while you're in there. OEM only.

 

Got the passenger valve covers off and they looked like they were in good shape. Don’t think the half-moons were the source of my leak, unfortunately. Good news is that I only had to do the one side to figure this out. Loosened the timing cover while I was in there and I am now fairly issue my leak is coming from the passenger cam seal. At least I was able to get the throttle body cleaned, replace the spark plugs, and PCV valve while I was in there so it wasn’t a total loss.

Decided to order the aircabinman OEM timing belt kit and will have everything done at the dealership this week.

 

Smart move
Then everything will be fresh. The 5VZFE was an awesome motor in my opinion. Nice torque and smooth

 

For future members, the cam seals certainly can leak. Toyota mechanic said they were gushing as bad as he had ever seen. If you’re experiencing a right or left sided engine leak that seems to be dripping from the corner of the timing cover, I’d strongly suspect cam seals.

Had everything replaced this week with the timing belt. No more leak.