1999 Honda Odyssey Overheating and blows cold air

VIVI1964

MEMBER
1999 HONDA ODYSSEY
6 CYL
FWD
AUTOMATIC
175,000 MILES

Hi there, my 99 Odyssey occasionally overheats (normally at higher speeds) and while it's o/heated it blows cold air out of the heat vents, even though the heater is on max heat. It only lasts a few minutes then goes back to normal, for every trip.
I've already changed the t/stat, and also tested the temp gauge, and changed the coolant temp gauge sending unit, and performed an air bleed on the cooling system as per repair manual.
Can you suggest any other tests or changes to fix this? I can't think of anything else except maybe water pump or head gasket issues, and hoping it's not! Could it be a faulty t/stat? Tried to test that too and seemed to open at the right temp.
Thanks for any help you can give.

5 Replies

IMPALASS

MECHANIC
3,112 POSTS

Hello -

For the overheating...

Open your hood and look at your two cooling fans. Start the car and see if they are turning. Turn the AC on and see if they turn... Let me know what you see here.

When it is blowing warm air inside - both heater hoses going in and coming out of the firewall should be hot. When it goes cold... Are both still hot or is one cold?

I take it you changed the items because of the symptoms it was doing... And still is doing the same thing?

Next, please go to Auto Zone (AZ) or O'Reilly's (OR) and for FREE they can pull the codes to the car. Most important: Once they check your codes, if they find something and you don't get it fixed and need to get back with us, please make sure you tell us exactly what the code was, number and all. Example, if the code was E0568 O2 Sensor bad. Then make sure you give us all of that. While there for FREE also they can bring their tester out and check your battery, alternator and starter.

Also is this a EX or LX

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Saturday, December 6th, 2008 AT 8:40 PM

VIVI1964

MEMBER
3 POSTS

Thanks ImpalaSS I'll explain a little more:
I did my own scan for codes, nothing came up.
Both cooling fans turn on occasionally, and definitely when I turn on the A/C.

I have a repair manual for this car and thought there is air in the system. So I did an air bleed by following the steps in the manual to purge it out and top up coolant.

As mentioned before I tried changing the temp gauge sending unit and the temp sensor, (and the thermostat of course), and after all this I still have the overheating problem at some point on every trip.

I'm worried it's the head gasket, or the water pump. Anyone had similar problems which got solved by changing these?

Thanks guys I'll try to return the favour with any of my own experiences.

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Monday, December 8th, 2008 AT 8:13 PM

IMPALASS

MECHANIC
3,112 POSTS

Hello -

Thanks for the info.....

Okay, fans okay... Yes good thinking on the air in the system; I did think about the air in the system but the heater comes and goes... That is an indication that either the water is stopping at the inlet of the heater core and not moving through it...(Blocked heater core) so one hose hot the other not, or not circulating very well, both cool down, the coolant not moving.

Did you get a chance to do the other check? When it is blowing warm air inside - both heater hoses going in and coming out of the firewall should be hot. When it goes cold... Are both still hot or is one cold?

My thought is since you have 175K..... Your radiator may be plugged and I would change my radiator cap also.

Still let me know about those heater hoses though.....

If it were the water pump... You should see leaks or the shaft is loose or the getting hot is not erratic.....

What type of coolant are you using?

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Monday, December 8th, 2008 AT 9:36 PM

VIVI1964

MEMBER
3 POSTS

Thanks again ImpalaSS.

The rad is not a problem, visually inspecting the elements seems clean. No obvious corrosion there.

The hoses as you said, when it's blowing hot, both are hot, and when it blows cold one is cold and one hot.

Now that you mention the coolant I put the green no-mix type. Tomorrow I'm going to the Honda dealer to buy their specified "type 2" I keep hearing I should have used. (Heard it's blue, but I bought this van used and it's had the green up till now)

You're right about the water pump if it was bad then I'd not have the heat etc working some of the time. (Duh)

I'll let you know, IF after all the fuss it was the wrong coolant all along?

Have a good weekend,
Vince

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Friday, December 12th, 2008 AT 6:57 PM

IMPALASS

MECHANIC
3,112 POSTS

Vince

Thanks for the update/info. . .. . .. . .just a couple of things. . .. . .. . ...

My idea on the radiator is that you may see the top looks okay. . .. . ..but it’s the inner coils, that may be plugged. . ..thus causing the overheating. The air should be moving through to cool and the fluid moving through the coils. You might also check to make sure the outside part of the coils is clean to allow good air flow. Many times folks remove them and have a radiator shop bore them out.

Since it is overheating at times. . ...you did bring up a concern for blowing a head gasket. . ..it if overheats too much. . ...it will.

Auto Zone is about $248 for one and the Radiator Barn is about $146.

Since one hose is hot and one not, that means the coolant is not moving through your heater core. If it were more constant I would say your core is plugged. It may be partially blocked or. . ..there may be air trapped. I would back flush the core.

So � since it was overheating prior to you changing the thermostat etc. . .. . .unless you got air in the system prior. . .. . .something may be partially blocked.

Another thought is your radiator cap. . .. . .if not in good condition it will also make the temp fluctuate.

Me, I would not worry about the exact Honda specific unless your feel it’s best. As long as you did a 50/50 mix of the green, that is still good. It needs to be 50/50 though.

Seems like you are doing a good job on the troubleshooting. . .. . .. . ...I again, am just a little concerned with why was it overheating at times in the first place before you did any work.

My suggestion if you do decide to change the coolant. . .. . .. . .. . .. . .

First, back flush the heater core to ensure good movement of liquid through the core.

Next, new radiator cap and bleed the air really good when you put the coolant in.. . ..

If that doesn’t work. . ...then go with the radiator. . .. . .. . .. . .(I guess as long as you know it isn’t the gauge acting up.)

Please keep me posted. . .. . .. . ..want to make sure we take good care of you.

Last, it looks like you may have some recalls on your vehicle. The dealer may fix these for free. Please contact the dealer service department, give them the VIN number of your car and have them check on these to see if they apply to you.