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Ok so here goes, Heat on my 2000 is almost nill.. Blower runs strong. I have checked the heat control valve and seems operational, when I turn the knob I can see the small metal pin move (on the firewall) in and out as I turn the knob as well as here something adjusting inside.
One of hoses to the firewall into the heater core is hot and the other is warm. I imagine this is the way it should be? I also replaced the cabin filter as some suggested with no change. If it were the thermostat I'd imagine I would not get a hot reading to hose to the heater core. Could it be a clogged core or perhaps air in the system. I'd never heard of a core clogging up, I know when they go bad they leak but this is not the case. I think heating on a vehicle is pretty straight forward , but this has me dumbfounded. Anyone please help with other suggestions. Please let it not be the core , else wife is getting a pair of warmer gloves and a heavier coat. Layers work best I advised her :)
 

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festor,

sounds like plugged core (hot inlet, cold or warm outlet). Try to remove the heater hoses and blast a garden hose through to see if you can free up any gunk. Reverse flow might be better here. Also, try to remove hoses from engine side since the firewall connections are more fragile. This should tell you if you had limited flow at first, and if it got better with some reverse/higher water pressure.

You guys use heat in Tampa? I guess cold weather is a relative term :)


couch
 

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Try some ear plugs or iPod so you can't hear the wife and dress warmly! LOL

Seriously, I bet the valve in question is messed up, or the temp blend motor is blown, they use a thin rubber diaphram typically, and your vehicle is old enough to have that go bad. usually heater cores either leak or something but fail to get hot sounds like either the blend door or the valve thing you talk about. Since I don't have one I'm not sure what I'm talking about LOL but I doubt it just clogged, that's not going to happen unless its in the hose.
 

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festor, clogging is a possibility, but if you've kept up on cooling system maintenance (drain & fill at appropriate mileages), you should not have that as a worry. I've taken apart a couple Honda radiators damaged by road debris, and if the coolant had been kept up, those radiators looked pristine. Same should go for the heater core.

Could be the valve, as mentioned.

The only way to check this stuff is to remove hoses and try to flush the core....I'll bet that if you run water through it using a funnel attached to a hose to the inlet, water will run right back out through the outlet. As well, see if the valve is actually working internally. I've removed one on our Accord (the Ody's is not very different at all), and you can clearly see if it is working by looking through it and moving the actuation arm.

Good luck.

OF
 

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Discussion Starter #5
Ok so I took it to the Honda dealer (they were running a $29 diagnosis special) after about 40 min the Service manager asked me to come speak with the mechanic that was 'diagnosing' the van. The mechanic ruled out the heater core , but said there something clogging the system on the Left (drivers)side of the engine. He had me touch a small hose near fender and said this hose should be hot as well. Long story short , he didn't know what the problem was and they wanted between $300-400 to continue diagnosing. I said 'no thanks' and pd my $29 fee.
 

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Just because your valve moves doesn't mean inside its working. Spend a few bucks on a new valve and replace it. That is almost always the problem on the 2nd gen vans from what I've seen. It was the problem on mine as well. Valve 'looked' okay but inside it had broken and was partially clogging the flow into the heater core causing the no heat situation. I tried the flushing and the thermostat replacement but this did the trick.
 

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Having the same problem...

""Our odyssey""" when you say change he valve...

PHP:
Just because your valve moves doesn't mean inside its working. Spend a few bucks on a new valve and replace it.
Where and what is the valve you are talking about

thanks..
 

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festor said:
Ok so here goes, Heat on my 2000 is almost nill.. Blower runs strong. I have checked the heat control valve and seems operational, when I turn the knob I can see the small metal pin move (on the firewall) in and out as I turn the knob as well as here something ...
The screw on the valve may be loose even though it doesn't look like it. See if you can tighten it. Set the thermostat to the lowest setting first.
 

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BAD THERMOSTAT is the problem. Stick with the simplest answer!

My Ody had little to NO heat on cold days unless I revved it up or was going really fast for a LONG time.
I replaced the T-stat with an 82 degree C thermostat which is a slight temp upgrade and I've had GREAT heat even on the coldest Chicagoland days and the Ody runs better.

T-stats are cheap and easy to replace.

PS: The thermostat is a DUAL stage part and if the bypass stage is stuck it will bypass the heater ALL the time.
 

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I had a similar problem on an '89 Caravan, would notice that the temp guage read just a bit lower than normal. changing the stat with an aftermarket didn't work either, replaced with the correct one for that engine fixed it. (over 100,000 miles had to do that a couple of times, each time OEM stat would be the answer)
One observation I had with that engine, was the stat would open, then modulate to keep the temp stable. A bad stat would just open too much and not modulate -- seems minor, but you could really tell when you wanted heat when it was cold.
 

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Repaired

The valve was broken on mine, it does not look like the best design
to put a bolt to hold a mechanism that is constantly changing
as soon as temperature vary.
Changed the valve, problem fixed
 

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I know this is an old thread. I am new here but have been searching for info. I recently picked up a 2000 ex with 260k. It had multiple problems. I have only one code left P0420 and the cat is bad. I had very low heat. I replaced in this order 1) cabin filter: filthy 2) heater valve; old one was ok 3) thermostat 4) drain radiator add flush and fill drive for a day. The next day and about 40 miles later I drained the radiator. I then put hose in radiator and flushed for about 10 minutes. I then removed the top hose on the front heater core and stuck hose inside it and clamped it. I flushed both the front and rear heater cores for 15 minutes. I then clamped the hose that comes out of the other side of the metal tee that i originally removed the top heater hose from. The water now was diverted back to the radiator and started pouring out the radiator instead of the point where the top front heater core hose was attached. I then reassembled and refilled with 50/50 mixes all. Ran the car with the rad cap off and shut down let cool topped off and then took for a long ride. BINGO Great heat. I probably should have started with a drain and flush and that probably would have solved my problem. I hope this helps.
 

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festor, did you ever get your heat up to snuff? I'm having the same issue - heat at the center vent does not get above 120F. I've had the cooling system flushed at Mr. Lube (bad idea, ended up lodging gunk in the rear heater core which I had flushed), Honda replaced the infamous heater valve near the firewall referenced above.

Next I'm going to have the tstat replaced because I don't think it's ever been done and I'm at ~240,000km. I'm also going to see if I can get the main heater core flushed.
 

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I'll add my tale of woe here as well. There are a lot of internet reports of heater failures like the ones described here, but very few success stories where doing X solved the problem.

We have had the thermostat, heater water diverter replaced, flushed the cooling system and still have nearly no heat. Our mechanic is wildly guessing at this point.

If you have had this problem and fixed it, please tell your story here!

Thanks,
Greg
 

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After the engine is at operating temp, feel both sides of the pipe by the heater control valve between the engine and the firewall with the heater set on high.
If you Ody has a rear heater, does it work? You could also try disconnecting the control wire at the heater water diverter and manually turning that valve to the max position (towards the engine, I believe). If it now works, it may be the heater control unit under the dash (pretty easy to get to) and there are several posts on how to fix that.
Buffalo4
 
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