1MZ-FE Rear Valve Cover Change - 299,000 Miles

[kschachn]

I had been meaning to replace the rear valve cover gasket on my '99 Sienna and finally got around to it today. This isn't easy to replace, the intake plenum has to come off plus a bunch of other stuff (including a very annoying wire harness). But I also had a new and improved rear cover and new style PCV valve that was sitting around gathering dust that needed to be installed. I also wanted to see what that back bank looked like after all these miles.

After nearly 300,000 miles I guess I didn't know what I would find under that cover. The back bank runs very, very hot compared to the front. Now mind you, this has engine been run exclusively on synthetic oil (almost all M1) since new with an OCI average of almost exactly 5,000 miles. There was one outlier run of 9,757 once (which may have been an recording error), and for the past couple of years I have been letting the interval creep up to around 6,500-6,800 miles.

I also changed out the O2 sensors as the back sensor is nearly impossible to disconnect otherwise, plus new spark plugs. The old ones were obviously worn compared to the new ones but otherwise looked OK.

Next up is a timing belt and water pump. The exhaust (catalytic converter) is sprouting a leak and I don't know what to do about that exactly. An OEM converter is $2000 and that seems a bit much for this old girl.

 

[kschachn]

For reference here is the front bank at 232,000 miles.

 

[hypervish]

Looking good!

I just put on a Bosal exhaust system front to back on my 98' Sienna.

 

[gregk24]

I have to say, for near 300K miles, that looks great. Thanks for sharing.

 

[JC1]

Looks pretty good. I'm Surprised there is some varnish if you used Mobil 1. My 98 Sienna has some varnish, but I'm really not worried about it.

When my exhaust was shot I replied it with a cheaper aftermarket. I needed to change the flex pipe last year again. Are you getting a CEL?

When did you last change the timing belt?

Regards, JC.

 

[Barkleymut]

Why would you worry about a Cat leak? Emmissions testing? Inspections? CEL?

 

[285south]

Originally Posted By: JC1
Looks pretty good. I'm Surprised there is some varnish if you used Mobil 1.


I'm surprised too that M1 left varnish. But 5K turned into 6.5K, reasonably sound to do, and I would say use a different synthetic oil to clean the decade plus of M1 OCI, preferably Redline 0W-30.

 

[Cujet]

The newer M1 oils leave an amber varnish. It "ain't" as clean as it used to be.

With the exception of M1 5W-40 Turbo Diesel Truck. That oil leaves my engines spotless! When I switched my 140,000 Mile Jaguar to TDT, it cleaned up the M1 amber varnish that was starting to build up. It also halved my UOA results. Even with greatly extended OCI's.

 

[kschachn]

I guess I thought it would look better than that even with all the miles. After all it has had a pretty good synthetic oil changed out on an almost ridiculously short interval. I can't imagine what it would have looked like on bulk dino, I probably wouldn't have made it 300,000 miles.

I don't know if it is the catalytic converter itself that is leaking, my comment was shorthand for the front pipe. There are only two sections to the exhaust, there is the front pipe with the "Y" section that also has the converter and then there is the rear pipe with the muffler. It is the front section that is leaking somewhere as it's making noise that is getting louder. I can hear it under the hood so I'm guessing one or both of the flex pipes. There is no CEL.

I might give the TDT a try. That varnish on the old valve cover was something, the front one is nothing like that. The way the engine is tilted in this car orients the rear cover directly right over the back manifold and cooks it to a crisp - obviously. Just how hot do you have to get M1 to turn it into black varnish?

Oh and I changed the timing belt about 100,000 miles ago, this will be the third change I have done.

 

[gfh77665]

Considering the Sienna is a known sludger, and its 15 years old with 300K, you are doing FINE. The M1 is not letting you down. Keep up your OCI's in the same manner and you will likely get another 100k.

Then, at 20 years old and 400k, sending it off to the great junkyard in the sky with some varnish, even heavy varnish, will be OK.

 

[Fraser434]

That engine is very clean, I did my apprenticeship at a Toyota dealer back when these were new and when sludge engines started coming in.

Timing belt is cake work, I'd recommend replacing the tensioner at the same time. Water pump you have to take the cam gears off and back plate off which sucks, matco/snap on sell a spanner wrench for the cam gears, makes it easier to get them on off, better off replacing the cam seals ar the same time, for all that trouble. At 300k I'd probably replace the idler pulleys onnthe front of the engine too.

 

[KrisZ]

Originally Posted By: kschachn
I guess I thought it would look better than that even with all the miles. After all it has had a pretty good synthetic oil changed out on an almost ridiculously short interval. I can't imagine what it would have looked like on bulk dino, I probably wouldn't have made it 300,000 miles.


I can't even imagine why anyone would think that a quality conventional would not do the job.
Here is a pic of a 300k sienna running on conventional, doesn't look that much worse than OP.

Link to the source

The car operates fine according to that poster and the OCI was equivalent to OPs. If all the hype about synthetics was true OPs engine should be spotless, but it's far from spotless. This thread is a nice proof of the hyperbole that surrounds synthetics.

 

[asiancivicmaniac]

Maybe we're looking at different pictures, but that definitely looks worse than the OP's engine.

 

[Barkleymut]

I agree, the OP's engine looks much better than this last pic, but then again if it runs fine then what is the harm in a vehicle that has almost no value and still runs fine? I have seen so many under the cover pics that make me cringe that one with just a little sludge or a lot of varnish really doesn't phase me much anymore.

 

[KrisZ]

Originally Posted By: asiancivicmaniac
Maybe we're looking at different pictures, but that definitely looks worse than the OP's engine.


Where did I say that the engine using dino didn't look worse?
But the original assertion was that the engine wouldn't even make it to 300k on dino, or at least have extreme slodge. And I simply provided proof that it's silly to assume so, just like it is silly to think that synthetics don't leave deposits.

 

[kschachn]

Yeah, I've already changed it twice in this car, plus I have helped a friend change his in a Camry twice. So this will be my fifth timing belt and water pump change in a 1MZ-FE. I have the wrench for the cam sprockets, and the installer tool for the cam oil seals.

As timing belt changes go I agree this one is pretty easy. The Accord is a lot harder as there is less clearance and you have to pin/index the two balance shafts.

Originally Posted By: Fraser434
That engine is very clean, I did my apprenticeship at a Toyota dealer back when these were new and when sludge engines started coming in.

Timing belt is cake work, I'd recommend replacing the tensioner at the same time. Water pump you have to take the cam gears off and back plate off which sucks, matco/snap on sell a spanner wrench for the cam gears, makes it easier to get them on off, better off replacing the cam seals ar the same time, for all that trouble. At 300k I'd probably replace the idler pulleys onnthe front of the engine too.

 

[synthetic_crazy]

Your engine looks great! I know from personal experience that these 1MZ-FE engines run very hot. Mobil 1 protects these engines very, very well. It is the only oil I will use in ours.

 

[Artem]

Originally Posted By: kschachn
Yeah, I've already changed it twice in this car, plus I have helped a friend change his in a Camry twice. So this will be my fifth timing belt and water pump change in a 1MZ-FE. I have the wrench for the cam sprockets, and the installer tool for the cam oil seals.

As timing belt changes go I agree this one is pretty easy. The Accord is a lot harder as there is less clearance and you have to pin/index the two balance shafts.


Why so many T-Belt changes? I'm coming up to 300k in my 98 Camry V6 with the same engine and this will be my third timing belt change. The first was at 95k. The second was at 210k and the third will be at a good 325k. All of mine looked good after 100k and could have easily gone longer, so why change em so much? Seems like a waste to me.

 

[kschachn]

All were done at 100,000 miles, give or take. It is two different cars.

Originally Posted By: Artem
Originally Posted By: kschachn
Yeah, I've already changed it twice in this car, plus I have helped a friend change his in a Camry twice. So this will be my fifth timing belt and water pump change in a 1MZ-FE. I have the wrench for the cam sprockets, and the installer tool for the cam oil seals.

As timing belt changes go I agree this one is pretty easy. The Accord is a lot harder as there is less clearance and you have to pin/index the two balance shafts.

Why so many T-Belt changes? I'm coming up to 300k in my 98 Camry V6 with the same engine and this will be my third timing belt change. The first was at 95k. The second was at 210k and the third will be at a good 325k. All of mine looked good after 100k and could have easily gone longer, so why change em so much? Seems like a waste to me.

 

[sciphi]

Looks good under there for 300k miles. I'd keep using M1 until it's no longer yours. If it's made it 300k miles and looks like a slight amount of varnish, something says it's working out fine.