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You should check to make sure both of the fans working.
1 on mine had brushes on fan motor stuck so it won't spin.
Odyssey got overheating when I was stuck in 100F going up a mountain while running A/C.
 

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... bigger radiator for longer life on water pump and any other parts to it.
I think the stock radiator has plenty of reserve cooling capacity. I have a screen (to catch bugs and road debris) in front of mine that probably reduces air flow by 10-15%. Even so, the ScanGuage reported no change in coolant temperature before and after installation.

When I was searching for a new radiator for my previous Olds, a local well-known radiator shop showed me the BTU ratings for the OEM (AC-Delco) and two compatible aftermarket products that they sold. The OEM was highest. The others were significantly less. Moral of the story: go with OEM to maintain stock cooling performance.

Dave
 

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Hello all,

I have a 2000 Odyssey that is just ready to turn 232,000 miles. This car has been one of the best I've ever owned and still runs strong and has always run cool, with the temperature gauge showing about 4 on a scale of 1-10.
Yesterday after making a short run, I noticed the A/C fluctuating a bit and did not think to check the temperature gauge at first but after a few minutes I did and saw it at about 7 on the same scale.

I was just pulling into my garage so killed the A/C and shut the engine off and let things cool down.

After 2 hours I checked the overflow reservoir and it was empty yet there were only a few spots of coolant on the garage floor. I checked the hoses and all seems good. I saw some coolant on the drivers side fan blades (these fans were replaced by my mechanic about a year ago). I topped off the reservoir with 50/50 coolant and managed to drive back to another destination of about 18 miles. The temperature gauge pretty much stayed around the 5 mark but occasionally went to 7 and then back to 4. This fluctuation seems odd.

I'm suspecting it may be the water pump finally failing as I opted not to replace it with the timing belt change at about 131,000 and at this stage I am due for the second timing belt change. Also visually seems there could be a leak in the upper section of the radiator in front of that drivers side fan. Sticking thermostat perhaps? But then why the leakage?

I have had the coolant serviced regularly over the years. Any opinions on what may be the issue?

Thanks in advance and I will continue to scour the forum.

Bob Seitz
Your in-dash temperature gauge is not linear. It will read at "4" while the temperature can vary maybe 30 degrees. The temperature is hottest on a hot day with the engine idling with the A/C running. That's when to look for a coolant leak. If the temp gauge goes above the mid-level hash mark the engine is starting to run hot, and the coolant will soon boil.

A loose or defective radiator cap could be at fault. Is coolant in your engine oil (you could see it on the dipstick)? That could indicate a blown head gasket, which could result from an engine severely overheating. The good news is that if you see coolant in your engine compartment, it's not in your oil!

Could it be that the radiator cap doesn't hold pressure and the fluid is blowing coolant out of the reservoir (a wildass guess)? You never mentioned if you could smell antifreeze or if you could see "steam" under the hood when it gets hot. If an engine is overheating, you may hear water boiling in the engine right after shutting it off, which is a great time to visually look for a leak.. If the water pump is leaking it will leak out of the timing belt cover near the bottom, in the vicinity of the crankshaft pulley. Newspaper under the vehicle may help pinpoint the leak. And - radiators are relatively simple to change out, if you DIY.

Someone else recommended replacing the radiator cap if you don't find the leak. Me too.
 

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I just went through similar situation on my '04 with 178K. It overheated half a mile from home and when it cooled down I went to fill with coolant via the radiator cap. It came off in three pieces! No pressure in the system resulted in lost coolant & overheating. I replaced the cap, added coolant and while burping the car saw coolant on the ground. I found that the water pump had developed a leak, probably when it overheated. Since it is behind the timing belt, I was in for a replacement of both. Almost $1300 later, all is well (except my wallet). I was due for a timing belt soon ( #2 ) anyway, but probably could have been all started with the radiator cap. The cap is less than $10.
 

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I think the stock radiator has plenty of reserve cooling capacity. I have a screen (to catch bugs and road debris) in front of mine that probably reduces air flow by 10-15%. Even so, the ScanGuage reported no change in coolant temperature before and after installation.

When I was searching for a new radiator for my previous Olds, a local well-known radiator shop showed me the BTU ratings for the OEM (AC-Delco) and two compatible aftermarket products that they sold. The OEM was highest. The others were significantly less. Moral of the story: go with OEM to maintain stock cooling performance.

Dave
Thanks Dave I'll stick with the OEM radiator then.
 

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Thanks Dave I'll stick with the OEM radiator then.
Koyo and Denso radiators are top notch for the Ody and can be found on ebay, etc for a decent price, inc shipping.
Just don't buy a cheaper unbranded one, like I did, :(
They are hard enough to change, at least for me, that it really pays to buy a quality one like Denso or Koyo.
Buffalo4
 

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Thanks Dave I'll stick with the OEM radiator then.
Re: radiator screens - a screen (1/16' x 1/16" window screen or similar) in front of the radiator significantly reduces airflow through the radiator more than you might think. I put one there and removed it when I saw what it did. I had a transmission cooler that dropped the transmission temp maybe 20 degrees on the highway with no screen. Surprise! The window screening reduced it to maybe 7-8 degrees. What I replaced it with is a stainless steel screen with 1/4" x 1/4" mesh. That stops the rocks and the big bugs, and lets most of the airflow through. The radiator seems to have ample cooling power. It is in stop and go summer traffic that the screen would possibly cause a problem. Remember - the dashboard temperature gauge reads the same, slightly below the hash mark, while the water temperature can vary 30 degrees or more. If you see the in-dash temp go over the midpoint hash mark, you're starting to overheat.
 

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Another rare possibility is that you lost some of the core capacity inside the radiator. Happened to me. It was running a bit warmer than I expected uphill, then next vacation on level ground. Then it spit up coolant, so I ran to a friends house since we were 100 mi from home. Spent 5 hours and 3 trips to Autozone. It would not have taken so long if it wasn't #1 in the dark, #2 116F outside and #3, a disorganized and packed full garage which required periodic tool searches. Plan to drain about 1/2 pint of tranny fluid in the changeout.
 

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Your in-dash temperature gauge is not linear. It will read at "4" while the temperature can vary maybe 30 degrees. The temperature is hottest on a hot day with the engine idling with the A/C running. That's when to look for a coolant leak. If the temp gauge goes above the mid-level hash mark the engine is starting to run hot, and the coolant will soon boil.

A loose or defective radiator cap could be at fault. Is coolant in your engine oil (you could see it on the dipstick)? That could indicate a blown head gasket, which could result from an engine severely overheating. The good news is that if you see coolant in your engine compartment, it's not in your oil!

Could it be that the radiator cap doesn't hold pressure and the fluid is blowing coolant out of the reservoir (a wildass guess)? You never mentioned if you could smell antifreeze or if you could see "steam" under the hood when it gets hot. If an engine is overheating, you may hear water boiling in the engine right after shutting it off, which is a great time to visually look for a leak.. If the water pump is leaking it will leak out of the timing belt cover near the bottom, in the vicinity of the crankshaft pulley. Newspaper under the vehicle may help pinpoint the leak. And - radiators are relatively simple to change out, if you DIY.

Someone else recommended replacing the radiator cap if you don't find the leak. Me too.
It was overheating for a while and came to find out I was low on fluid since my cap had broke ( how I have no idea) but I got a new one. But now its leaking a little from underneath which I'm pretty sure now my water pump is bad. I added fluid about a week ago and so far good. I hope it stays that way but I'll be checking on it from time to time. Here in Phoenix AZ it gets pretty hot in summertime but finally cooled down.
 

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Another rare possibility is that you lost some of the core capacity inside the radiator. Happened to me. It was running a bit warmer than I expected uphill, then next vacation on level ground. Then it spit up coolant, so I ran to a friends house since we were 100 mi from home. Spent 5 hours and 3 trips to Autozone. It would not have taken so long if it wasn't #1 in the dark, #2 116F outside and #3, a disorganized and packed full garage which required periodic tool searches. Plan to drain about 1/2 pint of tranny fluid in the changeout.
My cap had been the problem and was changed. So far it's good but at first had a leak, small but still for concern. So far so good but I will keep up with it. I've looked up on how to change water pump and man.....that's gonna be a duzzy.
 

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It was overheating for a while and came to find out I was low on fluid since my cap had broke ( how I have no idea) but I got a new one. But now its leaking a little from underneath which I'm pretty sure now my water pump is bad. I added fluid about a week ago and so far good. I hope it stays that way but I'll be checking on it from time to time. Here in Phoenix AZ it gets pretty hot in summertime but finally cooled down.
Too bad you're not in Tucson. I have a good Honda indy.
 

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But now its leaking a little from underneath which I'm pretty sure now my water pump is bad.
Cooling system leaks often occur after replacing a faulty radiator cap. The new cap restores the normal amount of cooling system pressure. Parts and seals are stressed by the pressure and any weak ones could leak.

Just for the record, avoid the temptation to add any leak-stopping chemicals to the coolant. Those can cause even bigger problems.

Dave
 

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Re: radiator screens - a screen (1/16' x 1/16" window screen or similar) in front of the radiator significantly reduces airflow through the radiator more than you might think. I put one there and removed it when I saw what it did. I had a transmission cooler that dropped the transmission temp maybe 20 degrees on the highway with no screen. Surprise! The window screening reduced it to maybe 7-8 degrees. .
That's a very good point about the radiator screen's effect on ATF temperature when an aux ATF cooler is installed.

The engine has a thermostat to regulate coolant flow through the radiator to maintain a constant temperature.

But the transmission doesn't. It pumps the same volume of ATF through the coolant loop regardless of temperature. So ATF temperature is inversely proportional to the amount of heat removed by the cooling loop. Reducing air flow would certainly reduce cooling thus leading to higher ATF temperature.

I have to check if my screen covers the ATF aux cooler. If it does, I will cut an opening for the cooler, or relocate it to behind the cooler.

Dave
 

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Cooling system leaks often occur after replacing a faulty radiator cap. The new cap restores the normal amount of cooling system pressure. Parts and seals are stressed by the pressure and any weak ones could leak.

Just for the record, avoid the temptation to add any leak-stopping chemicals to the coolant. Those can cause even bigger problems.

Dave
Oh that is so true about adding any stop leak, I avoid those since I don't want to have to add to any issue o may have and end up with something worse.
 

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I think he was referring to his trusted Honda independent shop...

Dave
 

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Now my 99 got a leak on the radiator.
Have you replaced yours with the Denso? $250 from dealer or $80 retrofit?
 

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Now my 99 got a leak on the radiator.
Have you replaced yours with the Denso? $250 from dealer or $80 retrofit?

Haven't checked around much but if that is truely a genuine Denso that fits your Ody, it is a good price---$89.99 with free shipping.
I would also advise installing a new radiator cap and an OEM thermostat. Upper and lower radiator hoses would also be recommended. Pretty easy to do when the radiator has to be removed anyways. :D

Buffalo4
 
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