Coolant leak after thermostat opens 2004 sienna - Toyota Sienna Forum - siennachat.com
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post #1 of 16 (permalink) Old 03-12-2017, 04:23 PM Thread Starter
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Coolant leak after thermostat opens 2004 sienna

I did a bunch of maintenance on my 2004 sienna this weekend.

1. New radiator, upper & lower hoses, thermostat and seal
2. Timing belt, tensioner, pulleys, and water belt, & new oil pump seal

I started it up and ran great. no leaks. Ran it again today, and now i'm getting a leak after the thermostat opens. I had issues on getting the upper engine mount off, and I'm afraid I tweaked the coolant outlet pipe.

Now, i'm looking for some brainstorming as I can't see where it's leaking other than its high on the engine. I confirmed it's not the thermostat housing, but obviously the water pump would be a chore to see. It drips down both sides of the engine, so I'd have a hard time believing it's the pump.

The manual is a joke in the html format and trying to find anything that shows me where the coolant outlet hose comes out is a big mystery. I can see the hose coming in to the outlet pipe portion that connects to the upper hose. I see coolant, but I'm not sure its leaking and it could be remnants of what may have split pouring fluid in.

Any one have any thoughts?
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post #2 of 16 (permalink) Old 03-12-2017, 04:49 PM Thread Starter
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Re: Coolant leak after thermostat opens 2004 sienna

One additional thing I just noticed, that below the back intake manifold, there is evidence of old cotton candy looking coolant leak. I can't see the cross over hose (does this engine have one? another thing I can't find in the FSM). So I wonder if thats what is failing. Seems like a big PIA to access that hose.
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post #3 of 16 (permalink) Old 03-12-2017, 05:26 PM
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Re: Coolant leak after thermostat opens 2004 sienna

I've seen posts about the metal plate leaking, which is UNDER the crossover hose. Got a pressure tester so you can confirm without the engine running?


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2005 sienna xle limited, 230k miles
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post #4 of 16 (permalink) Old 03-13-2017, 07:54 PM Thread Starter
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Re: Coolant leak after thermostat opens 2004 sienna

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Originally Posted by bsedgal View Post
I've seen posts about the metal plate leaking, which is UNDER the crossover hose. Got a pressure tester so you can confirm without the engine running?


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Thanks for the heads up. Your right there is some sort of plate below the cross over that is leaking. I just went ahead and started taking it apart. I didn't have to get to far to see the cotton candy.

Its basically the whole inlet housing. See last page in the engine mechanical > partial engine assy > last page of pdf

That's a PIA!

I've look around and can't find anyone that fixed it. Do you have any thread links to someone that did?

I'm pretty much there. I just have to take off the intake manifold, but I can't tell by the manual if that plate (inlet) will come off without taking the heads off.

In the order it has you place the inlet pipe first (its a liquid gasket (of course i'm sure the factory crap failed)) then the heads...
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post #5 of 16 (permalink) Old 03-13-2017, 08:01 PM
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Re: Coolant leak after thermostat opens 2004 sienna

Oh geez I dont think you have to take the heads off. Otherwise I'm sure this guy would have mentioned it...

Intake Manifold Gasket Coolant Leak on 2004ienna?

2005 sienna xle limited, 230k miles
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post #6 of 16 (permalink) Old 03-13-2017, 08:09 PM Thread Starter
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Re: Coolant leak after thermostat opens 2004 sienna

thank you sir thats what I needed. Diving in now...
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post #7 of 16 (permalink) Old 03-13-2017, 08:28 PM
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Re: Coolant leak after thermostat opens 2004 sienna

On my 2004 Sienna the Coolant inlet housing was leaking. I did not take the heads off. The inlet housing is held on by the bolts going through it. It does not have a gasket. It uses Toyota Seal Packing 1282B which is a silicone liquid gasket for Long life and Super Long life coolant (check ebay). I had to remove the knock sensors to remove the coolant inlet housing..

If you have ever changed the plugs you go through the same procedure with the added task of removing the intake manifold. I did not have to touch my heads to do this job. One extra bit of advice - cover all the openings that are exposed- ex intake manifold openings - you do not want to accidentally drop any crap into these.
You will need new intake manifold gaskets, the sealant I mentioned and a new intake plenum gasket. This job took me about 6 to 8 hours to do. Not difficult but time consuming. There are no tricks or quick ways to do this.
I would also plan on replacing coolant bypass hose #3 which is connected to the top of the coolant intake manifold and hidden until you remove the intake manifold.
Look at entry #19 in this post for additional info 2004 loosing coolant, don't no where

Last edited by Johnxyz; 03-13-2017 at 08:34 PM. Reason: additional info
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post #8 of 16 (permalink) Old 03-14-2017, 09:16 AM Thread Starter
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Re: Coolant leak after thermostat opens 2004 sienna

Quote:
Originally Posted by Johnxyz View Post
On my 2004 Sienna the Coolant inlet housing was leaking. I did not take the heads off. The inlet housing is held on by the bolts going through it. It does not have a gasket. It uses Toyota Seal Packing 1282B which is a silicone liquid gasket for Long life and Super Long life coolant (check ebay). I had to remove the knock sensors to remove the coolant inlet housing..

If you have ever changed the plugs you go through the same procedure with the added task of removing the intake manifold. I did not have to touch my heads to do this job. One extra bit of advice - cover all the openings that are exposed- ex intake manifold openings - you do not want to accidentally drop any crap into these.
You will need new intake manifold gaskets, the sealant I mentioned and a new intake plenum gasket. This job took me about 6 to 8 hours to do. Not difficult but time consuming. There are no tricks or quick ways to do this.
I would also plan on replacing coolant bypass hose #3 which is connected to the top of the coolant intake manifold and hidden until you remove the intake manifold.
Look at entry #19 in this post for additional info 2004 loosing coolant, don't no where

Thank you sir. That sums it up. I actually have everything off the intake manifold except the fuel line, which you provide me a great pdf to release that clip. I already had done the spark plugs when I did the thermostat / radiator so most of this stuff came off pretty quick.

I also have a crack in the outlet pipe (part that has the radiator cap) as I knock the upper engine stay into it when I couldn't get the stupid bolts out.

Well I should be able to get this done now... Thanks guys!
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post #9 of 16 (permalink) Old 03-14-2017, 07:43 PM Thread Starter
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Do you guys think permtex ultra grey or black would be an equivalent?

Dealership wants $100 and eBay is a distance for shipping 1282b.
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post #10 of 16 (permalink) Old 03-14-2017, 10:36 PM
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Re: Coolant leak after thermostat opens 2004 sienna

I think Ultra Grey would work. Another option: I used Permatex Right Stuff for that same repair on my '04 Sienna and it has held for the past 50K miles.
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post #11 of 16 (permalink) Old 03-18-2017, 03:51 PM Thread Starter
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Re: Coolant leak after thermostat opens 2004 sienna

Anyone that has done this repair, question.

I had to remove the knock sensor studs to be able to get the inlet housing out. I kind of seems it might have had some sealant on them, is that correct?


I found the section in manual on replacing the sensors, but I can't find the section where they take out the studs. I see the senors are 14lbs torque, but I can't find a torque spec on the studs...

Thanks, you guys have been a big help.
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post #12 of 16 (permalink) Old 03-18-2017, 07:02 PM
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Re: Coolant leak after thermostat opens 2004 sienna

When I did this I did not use any sealant on the knock sensors and as you mentioned the manual does not call for any. I can't be any help on torque for the studs. You are right about the 14# on the sensor torque. I didn't use a torque wrench for the sensors I just tightened them until I felt they were the same tightness as when I took them out. As far as the studs I wonder if they had anti-seize on them so that you would be able to remove them and they wouldn't seize in place.

Last edited by Johnxyz; 03-18-2017 at 08:01 PM.
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post #13 of 16 (permalink) Old 03-19-2017, 12:07 AM
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Re: Coolant leak after thermostat opens 2004 sienna

I only took out one of the studs to get it to clear. I also did not use sealant on the stud when reassembling and 'torqued' by feel.
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post #14 of 16 (permalink) Old Yesterday, 01:25 PM
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Re: Coolant leak after thermostat opens 2004 sienna

Thank you for the info. I went to replace the lower radiator hose yesterday and found a cracked inlet pipe instead. Removing that lead me to all kinds of cotton candy between the cylinder heads.

Manifold is coming off to see if it is the hose or the plate.

New hose, inlet pipe, spark plugs, thermostat seal and manifold gaskets so far. (Figure i will replace the spark plugs while i am at it.)

Any wisdom on re-using the thermostat? Car has 130K miles on it. No issues.

Anything else while i am in there.

Thanks
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post #15 of 16 (permalink) Old Yesterday, 01:41 PM
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Re: Coolant leak after thermostat opens 2004 sienna

I would make sure I cleaned the throttle body and replaced the PVC valve. When I did this job others on the site recommended this and they were right. My PVC valve cost $6.42 which wasn't too expensive and cleaning the throttle body involve some cleaning fluid, if memory serves me maybe $3.98. You may want to check the coolant bypass hose #3 which runs right over the top of the coolant inlet housing under the intake manifold I replaced this hose. Mine was fine but because of this hoses location and relative low cost I replaced it.
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