2004 Sienna headgasket leaking.

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NJC

Joined
Apr 28, 2005
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We purchased a 2004 Sienna in 2012 with 161K KM's, and it now has 347K KM's.

While under the van yesterday I noticed pink coolant dripping from back of engine. Yeah ... that's not a good sign. I like my coolant leaks near the front of the engine, where I can fix them. lol

It appears to be externally leaking coolant from head gasket. It's not evident in the engine (combustion or oil). But it's the death knell for a vehicle of this age / KM's, as it won't be worth fixing. I will try a stop leak product but that's a bandaid fix.

I called a shop familiar with Toyota's and he said this isn't a common problem.
 

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atikovi said:
Just because it isn't worth fixing, why is it the death knell for a vehicle? Just keep driving it and topping off with coolant as needed. Go another 100K no problem.
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Correct, it's a technical death knell. I will be doing that ... maybe one of the stop leak products will help a bit too.
 
I've never heard of an MZ series engine with HG issues barring extreme abuse

Are you sure the water plate under the intake isn't leaking and it's just running down?

Toyota/Lexus 3.3L V6 Water Inlet (Valley) Plate Coolant Leak

Tip: if you own a Toyota 3.0 (1MZ-FE) or 3.3 (3MZ-FE) V6 and you see a buildup of pink crust around the thermostat, your water inlet plate is leaking. If it is leaking badly, coolant will drip down the transmission. This issue seems to be common on older 3.0/3.3’s after 120k. For some reason I...
bobistheoilguy.com
 
michaelluscher said:
I've never heard of an MZ series engine with HG issues barring extreme abuse

Are you sure the water plate under the intake isn't leaking and it's just running down?

Toyota/Lexus 3.3L V6 Water Inlet (Valley) Plate Coolant Leak

Tip: if you own a Toyota 3.0 (1MZ-FE) or 3.3 (3MZ-FE) V6 and you see a buildup of pink crust around the thermostat, your water inlet plate is leaking. If it is leaking badly, coolant will drip down the transmission. This issue seems to be common on older 3.0/3.3’s after 120k. For some reason I...
bobistheoilguy.com
Click to expand...

Thanks for the advice. I hadn't heard of a leaking water plate ... based on the pic I took it seemed to be weeping from headgasket; IE I couldn't see anything above it. But I'll take another look with more light.

EDIT. I took off top plastic valve cover bezel and looked around with a flashlight in the valley. It was all dry.
 
Check leaks from hoses first before tearing up the engine.
My former 2004 Sienna have some coolant drip on the back also when I bought it but it was fine till I sold it (driven for 120K miles).
 
slacktide_bitog said:
If you plan on replacing the van, consider the 4-cylinder Sienna made in 2011-2012, if you can find one :)
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What's the allure with the 4 cylinder Sienna? They didn't last long on the market and from what I read the fuel economy wasn't much better than the 6 cylinder and they were under powered.
 
JC1 said:
What's the allure with the 4 cylinder Sienna? They didn't last long on the market and from what I read the fuel economy wasn't much better than the 6 cylinder and they were under powered.
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Ever try to work on a transverse V6? :sneaky:

I love Toyota, but their transverse V6 designs are particularly difficult, even for a transverse V6. And the minivans are even worse!

The 4-cylinder is much easier to work on, only has one cylinder bank, one valve cover gasket, and one head gasket. Changing spark pugs and valve cover gaskets would be no problem on a 4-cylinder.

Also, the 2.7L 1AR-FE has the same amount of power as the 3.8L V6 that Chrysler used at the time.

The 4-cylinder would be great for commercial usage, deliveries, and stop-and-go scenarios where the 4-cylinder really would've gotten better mpg than a V6 in real-world commercial use. Too bad they never made more effort in that market.

The new Sienna released for 2021 is exclusively 4-cylinder hybrid.
 
Look around under your thermostat, it is at the end of the coolant plate near the transmission, take off the air box cover and intake tube to get a clearer view. That does look like an external leak of the head gasket to which there is some head gasket repair stuff might be better suited to repair that kind of leak, I'd study that first, and of course Scotty Kilmer has a video talking about sealers, start at 5m for head gasket information, yes not everyones a fan, but I would point out the man does have a lot of wisdom and knowledge;


And if you go here you can see the later Toyota 3.5 has problems with external head gasket leaks;
Toyota and Lexus 2GR-FE 3.5L V6 coolant/head gasket leak
And more on the 3.5 at 6:30m this video;
 
The Critic warned me the valley plates do leak on Toyota V6s. Their UR-series V8s also have the same issues - the valley plate is also the main coolant passage between the rear of the heads and the T-stat.

the older UZ-series V8s were a “dry” design, a pipe and coolant bridge was used instead.
 
Use some Subaru Coolant Treatment (same stuff as Blue Devil for about 1/6 of the cost) This is exact type of leak it will fix.
 
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slacktide_bitog said:
Ever try to work on a transverse V6? :sneaky:

I love Toyota, but their transverse V6 designs are particularly difficult, even for a transverse V6. And the minivans are even worse!

The 4-cylinder is much easier to work on, only has one cylinder bank, one valve cover gasket, and one head gasket. Changing spark pugs and valve cover gaskets would be no problem on a 4-cylinder.

Also, the 2.7L 1AR-FE has the same amount of power as the 3.8L V6 that Chrysler used at the time.

The 4-cylinder would be great for commercial usage, deliveries, and stop-and-go scenarios where the 4-cylinder really would've gotten better mpg than a V6 in real-world commercial use. Too bad they never made more effort in that market.

The new Sienna released for 2021 is exclusively 4-cylinder hybrid.
Click to expand...
Yes I changed the timing belt on my Sienna back in 2010. What a pain in the butt it was to do.

Also changed the power steering pump twice and that was a total pain as well. Almost no room in some spots.

One of the reasons I bought a Caravan, there is actually more room in the engine bay to access stuff.
 
Our '97 Mazda MPV (Mazda JE V6, N-S orientation/RWD) developed a coolant leak in 2011 which I traced to a leaking head gasket. Coolant to exterior only, with no oil in the coolant and no bubbles in the rad.

I lived with it until 2014, and finally committed to tearing down the engine to replace both head gaskets, and fix the various oil leaks as well.

To my relief, the coolant leak was actually the result of loose intake-manifold bolts. The coolant had filled up the vee, and then ran along the head gasket and finally down the block. Totally fooled me!

I didn't change the head gaskets, and they never did leak over the next few years.

As others have suggested, a leak elsewhere can certainly present as a leaky head gasket.
 
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