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2008 Toyota Sienna Engine over heating


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BigChefff
New User

Feb 17, 2021, 4:30 PM

Post #1 of 7 (589 views)
post icon 2008 Toyota Sienna Engine over heating Sign In

Ok so I’m only a hobby mechanic and have run into something I can’t figure out.
My wife’s 2008 Toyota Sienna keeps running hot sporadically.
I’ve had a block test done which came back good.
Compression tested the radiator which also came back good.
Replaced the radiator cap and a hose clamp on the lower reservoir hose, topped off coolant.
Stopped running hot for about 8-9 days but the issue is happening again and the coolant level was low again after being filled up just over a week ago.
Van is parked in the same place everyday and I don’t see any leaks.
I have seen and can hear the fans running.
Any help or advice is greatly appreciated and I’ll answer any questions I can to help on my end.
Removed e-mail


(This post was edited by Hammer Time on Feb 17, 2021, 4:37 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 17, 2021, 4:45 PM

Post #2 of 7 (574 views)
Re: 2008 Toyota Sienna Engine over heating Sign In

Ok, first let me correct a few things you said

Block test - Totally unreliable. The only time those thing return a positive test, the problem was already totally obvious with steam out the back.

Leaks - Many leaks burn off on hot engine or exhaust and never hit the ground.

You obviously have a coolant loss somewhere that you just haven't found yet. You could still have a blown head gasket. They are very hard to confirm. You could also have a leak that is slow enough to avoid detection. You would need to do a pressure test and keep it under pressure for 1/2 hour or more and examine it very closely with a flashlight.

PS, I removed your email as that will expose you to some ruthless spammers. We don't respond by mail anyway.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



BigChefff
New User

Feb 17, 2021, 6:57 PM

Post #3 of 7 (560 views)
Re: 2008 Toyota Sienna Engine over heating Sign In

Ok I was only going off of what my really good friend who owned his own shop for 45 years was telling me.
Thanks for the info.
The motor itself has about 85k miles on it and it’s never been run into the red. Wife knows if it’s starts climbing to pull over and let it cool down from a junker we had when we were younger.
It’s not driven hard and always has maintenance on time.

Compression test on what though?
The radiator was compression tested during the same visit I had the block test done and the visual inspection of the head.

Again I’m good with my hands from being a chef for a bit over 20 years but I know how to follow instructions and do the majority of my vehicle repairs myself as long as I have the appropriate tools.

Thank you for your time in helping me with this.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 17, 2021, 7:03 PM

Post #4 of 7 (556 views)
Re: 2008 Toyota Sienna Engine over heating Sign In

I never said anything about compression.

You need to do a long cooling system PRESSURE test.

Don't rule out anything based on history. The only accurate way to test for head gasket is with an exhaust analyzer to sniff for hydrocarbons at the radiator. Nothing else is very reliable.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 17, 2021, 8:28 PM

Post #5 of 7 (545 views)
Re: 2008 Toyota Sienna Engine over heating Sign In

I didn't see this thread for some reason.

Question and problem is one thing said up near top of this already. "You added coolant" to this cooling system, VOILA!

It has air or vapor in it somehow or someway either defect or not properly filled IMO find that now and fix that if you vacuum fill coolant is the only, perhaps the only way on this vehicle,

T



BigChefff
New User

Feb 23, 2021, 2:48 AM

Post #6 of 7 (488 views)
Re: 2008 Toyota Sienna Engine over heating Sign In

After having both the exhaust sniff and the long system pressure test done which both checked out.
Found a very small hole in the lower part of the coolant reservoir tank close the the hose.
Replaced the fan shroud/res tank combo part and so far haven’t had an issue.
Will update the thread if I have any further issues from overheating.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 23, 2021, 8:04 AM

Post #7 of 7 (482 views)
Re: 2008 Toyota Sienna Engine over heating Sign In

That can cause this problem! Fix or replace?

Some can be fixed with Permatex, clear adhesive/sealant if new or good used not available or practical right now. Assorted ones can require removing other parts that might bust do replace hose to it with proper hose! Just found locally was impossible to find is an unusual size by chance just happed Advance Auto knew what I was after, Tom







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