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Discussion Starter · #1 ·
I've been following a thread regarding the thermostat change from a 78 to 82C thermostat in the Odyssey and I just wanted to get an update on whether or not there was a Honda dealership available thermostat that would fit in the J35A7 VCM enabled engine. The threads about the t-stat seem to all coincide with a Motorad replacement however, I've had nothing but pure bad luck with them in the last 6 cars I've tried them on and have had 100% success with the Honda dealer purchased ones.

The issue I've had is leaks. Despite putting in a new gasket and installing them properly they seem to always have a slight leak to them.

So long story short is there no t-stat from say an Acura MDX or a new Accord or equivalent car with a J35 that uses a hotter t-stat?

To my knowledge from reading old threads Nippon, the supplier of t-stats to Honda doesn't make this particular one in a 82C variant.

Winter is coming soon and its cold out tonight...
thanks,
 

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Steve,

Couple things:

1. Motorad comes in 2 flavors:
- Standard... PN 302-180 (this is what I have now.....zero issues whatsoever)
- "Fail-Safe"...PN 7302-180. In theory, nice idea but even under normal operating temp, these tstats are known to wedge open in "Fail Safe" mode, causing a cool-running engine.

2. Gasket: use only Honda gasket.
Remember that the gasket has a groove where the tstat flange fits into (like a sandwich).

If you use Motorad tstat (PN 302-180) and Honda gasket (this exactly what I have), you should have zero issues.

BTW, you will need one gallon of Honda coolant because during the tstat change, you will lose roughly 3.5L of coolant (unless you drain the radiator first!).


For those reading this thread, here is the 82C tstat thread DIY. Very easy to perform:

http://www.odyclub.com/forums/52-20...t-changed-82-deg-c-motorad-thermostat-19.html
 

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Discussion Starter · #3 ·
Honda thermostat

Thanks CNN,

I figured that there likely wasn't a genuine Honda t-stat for the van as I'm sure many others like myself have probably looked high and low before.

In any case, yes you're correct in using the Honda gasket with the Motorad t-stat. I think what turned me off from Motorad in the past was the fact that everytime I put one in using the Motorad gasket that it's caused me nothing but headache and having to re-do the t-stat over and over and over again becomes a huge waste of coolant a more importantly a waste of my time hence why I stopped buying them when I fix cars for ppl.

I have read that buying the fail safe version isn't the best thing to do b/c apparently the t-stat can open a hair too far and then get jammed open even though the van isn't overheating. Best to stick with the regular version I think.

Since my van has 63, 000 miles on it I guess I'll drain the block and rad before I even bother removing the t-stat and just put in all new coolant too. Any tips to save me from having to look where the little block drain petcock is? I'm assuming right by the oil filter region and its probably a 12mm purge bolt like the one on my Honda civic.

I have small little hands so I'm sure swapping out the t-stat would be as easy as doing a 95 Accord V6.

Thanks!
 

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...Any tips to save me from having to look where the little block drain petcock is?...
Hello Steve,

Option 1:
- This is a picture from Honda Diagram, it is PN 90001-PM3-003.
- Right below cylinder #6 (Front leftmost cylinder).
- It requires 19-mm wrench, and is on super-tight like a wheel lug, you may scrape your knuckle doing this!
- If you do this from below, get out quickly just when the bolt comes loose, otherwise you get a shower of coolant.
- Note: there is a connecting pipe that connects the REAR (cylinders 1-2-3) and the FRONT (cylinders 4-5-6), so coolant may travel from the REAR to FRONT blocks and vice versa.

Option 2:
- Disconnect lower radiator "pet cock" (remove the plastic shield first).


Whatever option you decide, first remove the old tstat, then flush through the opening in the engine block and the upper rad hose, water will flow down and out of the rad pet cock.

PS: the problem is Honda only sells premixed coolant, which is 50-50 ratio.
Now you have water in the system that dilutes it further!
I have been to Calgary before in the winter and I will tell you this: with Calgary winter, you need a 60-40 coolant ratio (60% is coolant)!!!
- Check with the Honda dealer if they sell concentrated antifreeze (undiluted)
- If not then use Prestone Antifreeze (undiluted). I have used Prestone for many years, zero issues.


 

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Discussion Starter · #5 ·
I thought that someone here had posted a little DIY Honda service document showing that there was an actual petcock valve on the back of the block to remove the old coolant. The location you've specified is basically the same exact spot where my block heater in my 1991 Honda Civic is.

I'm surprised that car makers don't make an easy access plug to drain coolant like one that is used to drain like a transmission or engine oil....

Oh well, looks like I'll just make the mess in my garage and clean up afterwards.

Yes Honda does make a concentrated "dark green" colored coolant.

I am 100% positive that its available as I've purchased 5 cases from Honda recently.

The odd thing is that the coolant isn't something that is clearly listed in their parts catalog - even the parts manager couldn't find it intially. I had an older honda parts catalog that showed pictures and parts # of all their fluid line from 5 years ago and that concentrate was listed. After much arguing at the parts counter they found it and ordered it in for me. Right now my cars all have a 60/40 mix in it.

Thanks!
 

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Don't remove the drain bolt at the front if you also drain the radiator. Instead open the petcock at the right rear of the block - part 15 in the diagram above. You can also attach a plain rubber hose to it and save making a big mess in your garage.

You can reach the petcock from under the van by reaching up high or from within the engine bay if your hand is flexible.

BTW, that front drain bolt is where the Ody's block heater goes.
 

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Discussion Starter · #8 ·
excellent feedback guys. I figured that huge cap on the front of the block was for a block heater. I've remove that from other engines (mainly civics) but since my van already has a block heater then I might as well save myself some mess by draining it in a more controlled manner via the back drain petcock.

I'm assuming a 12mm wrench is all that is needed to open the valve?

When I drain the rad and the block from that valve does that mean that I've drained almost 90% of the coolant? Since my van has the original Honda coolant from the factory in it and my mileage isn't that high that I can simply do a drain of the block and rad and then fill up? How does one remove all the old coolant from the rear heater or is that coolant essentially stuck there until I either force flush it via a garden hose or just refill with fresh coolant to "refresh" that residual in the pipes going to the rear?

Since I'm asking all these questions I might as well ask how much coolant mixture do I need for a full drain of block and rad? I'm assuming at least 6 liters.

Thanks,
 

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I fitted one of the 82 degree C t-stat in my '07 a couple of weeks ago. While it hasn't gotten crazy cold yet, that thing will flat run you out of the cabin when set on full hot. Holy Cow! I followed cnn's DIY and just dropped the t-stat housing. Yes it makes a mess but not that big a deal. Buy the o-ring gasket from your dealer about an hour or so to do everyting start to finish. Bring on winter!
 

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Steve, the drain takes a normal-size wrench but I'm not sure of the exact size. Just loosen it, don't remove it, like with a brake bleeder fitting.

Draining the radiator and the block removes about 6 litres of coolant out of 9 1/2. Don't forget to change what's in the overflow tank too.

There's no drain for the rear heater. Just let the new mix with the old, like we do with the transmission fluid. That's why the first coolant change is after 10 years but the second is after only 5 years.

I wouldn't flush it with water. There would be no way to know how much water is inside so the mix would be unknown. Also, it's not good to leave municipal water in there because of the minerals and stuff.
 

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Discussion Starter · #11 ·
Well I finally did the T-stat swap out and holy sh*t does it blow hot now. Nothing compared to my original t-stat. I was breaking a sweat driving.

One thing I noticed that its about 2C outside and after a 15 KM drive the thermostat hose is pretty much cold while the other large hose beside it was hot. Engine temps are running exactly where they should be so I'm assuming the t-stat is blocking the coolant flow to keep the heater blowing hot?

Crazy how 5C difference can make a heater feel warm vs. hot.

Hoping that fuel economy will improve now too.

Thanks everyone for such a killer tip.
 

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...One thing I noticed that its about 2C outside and after a 15 KM drive the thermostat hose is pretty much cold while the other large hose beside it was hot...
This is normal for any car, once the hot coolant runs through the radiator, it is cooled down.
Nothing to worry about.

- Periodically check your coolant reservoir, after such a tstat change, it may take a few days for the coolant level to settle down (as air bubble if bled out of the system).

- Enjoy the Calgary winter LOL!
 

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I'm having a hell of a time finding this stat for my Odyssey. Absolutely no luck locally. Can any one recommend an online retailer for it?
 

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Thanks, I just ordered it from Amazon ( which I always forget about ). I was searching Motorad on ebay with no matches, but when I just put in the numbers that worked. Thanks again
 

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I haven't seen any improvement in fuel economy nor have I seen it deteroriate either since my t-stat change. We are running out warm days around here so my experiment with this mod will have to be suspended as winter blended fuels will be the order of the day for the next several months. With that comes a seasonal loss in fuel economy.

That being said I wouldn't necessarily expect better fuel economy with the hotter t-stat. As I would be more inclined to believe you would have better performance from as cool of an air/fuel mixture as you can get as its a density thing. This is especially true in normally aspirated engines, which I know our modern engiens are not. But some modern fuel injected engiens run a small portion of the the engine's coolant to the throttle body/air plentium to cool the air/fuel mixture. If my fuel economy stays in check after this mod I would be more than satisified.
 

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I haven't seen any improvement in fuel economy nor have I seen it deteroriate either since my t-stat change.
My fuel economy in the summer long trips is about 24-25 mpg.
Weight: 2 adults, 4 kids and standard luggage in the trunk.
Tire pressure at 35-38 psi.
Average speed was: 65-75 mph in the Midwest, no big hills/mountains.


...But some modern fuel injected engiens run a small portion of the the engine's coolant to the throttle body/air plentium to cool the air/fuel mixture.
I believe this setup of coolant hose feeding the throttle (as in Ody and my 1998 BMW also has this setup) is to bring hot coolant to the throttle to prevent ice build up during cold weather, and not to cool the mixture.
 
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