Boiled Ballz -- SOLVED

[Valkorado]

So I take the Silver Bullet out for a nice, brisk ride today weaving through the blessed tourists and enjoying some twisties.  Finally made 80* here, but I was experiencing schwetty balls more than expected for a Gunnison summer day.  Got home and shut down, and she's a bubbling at a full boil.  Pulled the left side cover and the overflow was like a cauldron, bubble bubble toil and trouble.    Temp light never came on.

I remember reading there's a module behind that radiator overflow tank that controls the temp dummy light on early models (this one is a 97 Tourer).  Either way, I'm overheatin'.  Where to start?

[indybobm]

Did the fan come on?

[Valkorado]

Did the fan come on?

No, but thanks for asking.  I was just in the garage trying to cool the hot mama down.  I grounded the switch, the fan does work.

I got behind the overflow tank, the temp module looks good, and is attached to the wiring.  Got me wondering.  I did replace the 3-pin flasher module behind that a while back with a 2-pin LED flasher.  Could that missing pin connection somehow be disabling the temp module?

[Valkorado]

Digging around some more.  Sending unit (thermo switch) bad?

EDIT: Ordered a thermo switch, 37760-MT2-003.  Hopefully that will do the trick!  I know I'll need to drain the antifreeze to install this switch, will I also have to pull the radiator?

[Gryphon Rider]

If it's running hot while you're moving relatively fast, I'm thinking failed thermostat.

[Tfrank59]

 yes thermostat first. something is preventing  adequate circulation in the system so the first place to look would be the thermostat not opening. Too bad it's such a pain in the butt to get to it. Let us know what you learn

Well my own comment about the difficult access to the thermostat made me think what about your water pump, is it functioning properly? Might want to check that out since it's fairly easy to do so.  Just a thought

[Valkorado]

Thanks for your replies.

Uggh, I was hoping not the thermostat.  I tested the 2-pin LED flasher theory, that had nothing to do with it as suspected.  I guess since I already ordered the thermo switch I'll install that first, if no luck I'll check the pump and thermostat.

Would the fan and thermostat still function if the temperature indicator unit is not working?  The temp indicator light does not come on when the key is turned on.

[Tfrank59]

Thanks for your replies.

Uggh, I was hoping not the thermostat.  I tested the 2-pin LED flasher theory, that had nothing to do with it as suspected.  I guess since I already ordered the thermo switch I'll install that first, if no luck I'll check the pump and thermostat.

Would the fan and thermostat still function if the temperature indicator unit is not working?  The temp indicator light does not come on when the key is turned on.

I think your temp light is simply not working, and should be, but that's a separate issue.  Looking at you location I was wondering if the high altitude there in CO has anything to do with the bike running so hot...again just thinking out loud.  doesn't the alt. affect other carbureted vehicles there? I remember driving an old mercury through the vail pass in 1989 and it was dogging so badly, and running very hot--carb was set for Seattle which is basically sea level.  Huge RVs were passing me like I was standing still

[Bagger John - #3785]

Check the fan thermostatic switch.

It's separate from the temp indicator circuit.

Next, check to see if the fan motor energizes at all when its control lead (which usually hooks to the switch) is grounded.

[Valkorado]

I think your temp light is simply not working, and should be, but that's a separate issue.  Looking at you location I was wondering if the high altitude there in CO has anything to do with the bike running so hot...again just thinking out loud.  doesn't the alt. affect other carbureted vehicles there? I remember driving an old mercury through the vail pass in 1989 and it was dogging so badly, and running very hot--carb was set for Seattle which is basically sea level.  Huge RVs were passing me like I was standing still

Altitude sucks a little power, but I rarely have vehicles passing me.       Sure hope it's the sending unit as opposed to the thermostat or water pump.  I'll update after it arrives.

[longrider]

You've got some good suggestions   A little more info would be helpful.  Did you notice the heat while riding highway speed.  Or when you were almost home in stop and go traffic.  If  not hot on the highway then your fan is not working correctly.  If you noticed it on the highway as well then I agree with the thermostat.  On our tourers the rad is easy to remove. I use a 1/4" drive socket for the back bolt on the t stat.  A new rubb r gasket should be used.  Remember to burp the rad by starting the engine for a moment on install.  While you have the rad out take the time and wash  it out from the backside.  Lay it on a nice large rag on the floor and give it a wash with a pressure washer that is dialed back and don't get too close.  You won't believe what comes out of it.  I think a new fan switch in the rad is a good idea as well. 

[Valkorado]

You've got some good suggestions   A little more info would be helpful.  Did you notice the heat while riding highway speed.  Or when you were almost home in stop and go traffic.  If  not hot on the highway then your fan is not working correctly.  If you noticed it on the highway as well then I agree with the thermostat.  On our tourers the rad is easy to remove. I use a 1/4" drive socket for the back bolt on the t stat.  A new rubb r gasket should be used.  Remember to burp the rad by starting the engine for a moment on install.  While you have the rad out take the time and wash  it out from the backside.  Lay it on a nice large rag on the floor and give it a wash with a pressure washer that is dialed back and don't get too close.  You won't believe what comes out of it.  I think a new fan switch in the rad is a good idea as well. 

All I can say for sure is it was mucho caliente after a brisk lakside ride (highway speeds and then some) -- like fry up some bacon and eggs on the valve covers hot.  Dang.  I don't really want to do the radiator drain/uninstall old part/install new part/refill/ AND THEN HAVE TO REPEAT!!!  Doesn't sound appealing.  Maybe I'll order the thremostat as well and kill both birds with the same stone.  Hopefully it'll be good for another 20+ years (1996 made bike). 

Oh yeah, how to burp a radiator?  Put it over my shoulder and pat its back?

[sandy]

Just fill and run it with the cap off. When the T stat opens, the level will drop. Now rev it a few times and refill. Check it again after a ride.

[Valkorado]

Woo-Hoo!  The Silver Bullet is back!  Being the highly skilled mechanic I am and since I love wrenching so, I figured I'd try the easy stuff first.  I decided to start with the temperature indicator unit first, then the the switch, and if neither of those panned out I'd move on to the thermostat and as a last resort the water pump.  

I checked around, and the temperature indicator unit is OBSOLETE.  NADA.  ZIP.  ZILCH.  Partzilla had it listed at $60.20, again obsolete.  I got mighty nervous and started looking around for 38710-MZ0-003 everywhere, no luck.  Couldn't even find it used.  Then, I saw a picture of an identical looking the part listed as a fuel pump relay.  Ordered it up, less than 15 bucks. It arrived today, and  IT WORKED!  Plug and play easy!  My temp light it's back, and my fan kicks on when the radiator gets hot!

Look for a TL-97A fuel pump relay -- it's actually the 38710-MZ0-003 that you won't find anywhere.

Hope this helps anyone who find themselves in a similar predicament.

TIME TO RIDE!

[Bagger John - #3785]

Look for a TL-97A fuel pump relay -- it's actually the 38710-MZ0-003 that you won't find anywhere.

Is this a Honda P/N, some other OEM or a generic?

[Valkorado]

OEM but not made by Honda.  Branded Shindengen, exactly like the unit that came out.     And eactly what Honda was calling 38710-MZ0-003 that is now discontinued.

Ge 'em used while they're hot.

[Tfrank59]

Great news.   

[Bagger John - #3785]

OEM but not made by Honda.  Branded Shindengen, exactly like the unit that came out.     And eactly what Honda was calling 38710-MZ0-003 that is now discontinued.

Ge 'em used while they're hot.

Got a link for us dummies?

And the 2000-up models don't use this part. IIRC, there's a Tech thread on how to convert a 97-99 over to the later model setup.

[Valkorado]

Got a link for us dummies?

Here ya go.

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR0.TRC0.H0.TRS0&_nkw=TL-97A+fuel+pump+relay&_sacat=0

[mrgeoff]

Valkorado...It seems like great minds think alike...Just yesterday I was searching for a replacement for my 1999 CT Temperature Indicating Unit that is not available any more...I came across this same relay : 96-04 Honda Magna 750 Vf750c Relay Indicator Unit module 38710-MZ5-003...Notice that the number is a little different  ( MZ0 and MZ5 ), but they are the same relay...check out this site...
http://www.ebay.com/sch/Electrical-Ignition/179853/i.html?_pgn=4&_skc=150&MMake=MZ
Scroll down to the relay unit... I really believe that this will work too...!!! Going to buy on and will get back to ya'll...I like the info you found too...I will definitely buy one of them too...!!!

[Valkorado]

Valkorado...It seems like great minds think alike...Just yesterday I was searching for a replacement for my 1999 CT Temperature Indicating Unit that is not available any more...I came across this same relay : 96-04 Honda Magna 750 Vf750c Relay Indicator Unit module 38710-MZ5-003...Notice that the number is a little different  ( MZ0 and MZ5 ), but they are the same relay...check out this site...
http://www.ebay.com/sch/Electrical-Ignition/179853/i.html?_pgn=4&_skc=150&MMake=MZ
Scroll down to the relay unit... I really believe that this will work too...!!! Going to buy on and will get back to ya'll...I like the info you found too...I will definitely buy one of them too...!!!

Yep, same unit functionality wise.  And more of 'em available. 

http://www.ebay.com/sch/i.html?_odkw=TL-97A+fuel+pump+relay&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.TRS0&_nkw=38710-MZ5-003&_sacat=0

[ridingron]

 TL-97A   Is this a Honda P/N, some other OEM or a generic?  

Generic. Every Honda part number I've ever seen was in the "38710-MZ0-003" format, 5 numbers-3 letters/numbers-3 numbers.

[Valkorado]

 TL-97A   Is this a Honda P/N, some other OEM or a generic?  

Generic. Every Honda part number I've ever seen was in the "38710-MZ0-003" format, 5 numbers-3 letters/numbers-3 numbers.

Nope, not generic. If you have a 97-99 Standard or Tourer pull yours out and look at it.  Shindengen TL-97A will be clearly visible on the relay.  Honda called this part 38710-MZ0-003 before they discontinued production of it.

BTW, Honda contacts out much of their "OEM" stuff, like relays, etc..

[gordonv]

Anything like these?

http://goldwingdocs.com/Store/Goldwing-GL1500-Relay-G8MS-H30.asp

I think all the 5 relays are the same on the IS. I can't see that they are not available as you found, from the original manufacturer.

[Valkorado]

#16, "part obsolete".
http://www.partzilla.com/parts/search/Honda/Motorcycle/1997/GL1500CT+AC/WIRE+HARNESS/parts.html

[Tfrank59]

Got a link for us dummies?

Here ya go.

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR0.TRC0.H0.TRS0&_nkw=TL-97A+fuel+pump+relay&_sacat=0

Hey I really appreciate the information. It's good to know that there's some interchangeability with this part from other Honda models. I'm not crazy about the fact that it is a used part – is there no way to get these new? I kind of gathered that from the thread here and everybody's responses.  I guess if we have to go with used we do it, but it would be nice to know if there is a vendor out there selling these parts new, especially since they are electrical parts.

[mrgeoff]

I'm thinking about buying one just to cut it open and see if I can figure it out...Shouldn't be to difficult...!!!

[Bagger John - #3785]

Look what we have here, gang:

http://www.partzilla.com/parts/detail/honda/HP-38710-MZ5-003.html

Showing as still current/in stock.

For comparison purposes I searched that site for the '97-'99 GL1500C part and it comes up "Obsolete".

Since I need a few goodies for one of my Valk projects, I'm going to add this to my order.

[indybobm]

The Temperature Indicator Unit is an electronic module. It takes the voltage reading from the Thero Unit on (#9) the thermostat housing and depending on the voltage (based on water temperature) decides when to turn on the coolant light.
Some cycle refitters do not not what it is and call it a fuel pump relay. It is not a relay.
There are similar units used on different models of Hondas but they are calibrated differently for that bike.
The Temperature Indicator Unit has nothing to do with turning on the fan. Proper operation of the fan is controlled by the Thermo Switch Assembly on the lower rear corner of the radiator. This switch can go bad and connection at the switch can get corroded. When the engine water temperature reaches 208 - 216 degrees, the switch turns on the fan until the temperature goes back down to below 199 - 207 degrees.

[jim@98valkyrie.com]

The Temperature Indicator Unit is an electronic module. It takes the voltage reading from the Thero Unit on (#9) the thermostat housing and depending on the voltage (based on water temperature) decides when to turn on the coolant light.
Some cycle refitters do not not what it is and call it a fuel pump relay. It is not a relay.
There are similar units used on different models of Hondas but they are calibrated differently for that bike.
The Temperature Indicator Unit has nothing to do with turning on the fan. Proper operation of the fan is controlled by the Thermo Switch Assembly on the lower rear corner of the radiator. This switch can go bad and connection at the switch can get corroded. When the engine water temperature reaches 208 - 216 degrees, the switch turns on the fan until the temperature goes back down to below 199 - 207 degrees.

Great information, thanks for clarifying it! I had thought that since it was a "relay", we could figure out how to sub out a generic part for it. Your explanation of it being electronic and having different set points based on application, clears that up really quick.

[Valkorado]

The Temperature Indicator Unit is an electronic module. It takes the voltage reading from the Thero Unit on (#9) the thermostat housing and depending on the voltage (based on water temperature) decides when to turn on the coolant light.
Some cycle refitters do not not what it is and call it a fuel pump relay. It is not a relay.
There are similar units used on different models of Hondas but they are calibrated differently for that bike.
The Temperature Indicator Unit has nothing to do with turning on the fan. Proper operation of the fan is controlled by the Thermo Switch Assembly on the lower rear corner of the radiator. This switch can go bad and connection at the switch can get corroded. When the engine water temperature reaches 208 - 216 degrees, the switch turns on the fan until the temperature goes back down to below 199 - 207 degrees.

Thanks for the information.  Now I'm going to double check that thermo switch since I have a new one sitting right here.

Aaaaaand...  the Woo-Hoo has become a Boo-Hoo.  I was thinking since I didn't have an indicator light before replacing the part and I did have the light after installing it my problem had been solved.  After reading IndyBob's post I wasn't so sure.  Warmed it up, no fan joy.  Drained the antifreeze and installed a new thermo switch assembly, filled the radiator again and warmed it up.  TO A @#$& boil!    Damn, looks like thermostat will be next.  Then the water pump???

[indybobm]

I grounded the switch, the fan does work.

First question, when you grounded the wire from the fan, did you ground it to the radiator or the bike frame? If the fan does not come on with the wire grounded to the radiator but does come on when you ground to the frame, then the radiator is not properly grounded to the frame.

If the fan comes on when you ground the wire to the Thermo Switch on the radiator but the fan does not come when the engine is hot, the Thermo Switch must be bad. Also remember that the fan gets its ground through the Thermo Switch and through the metal radiator.

[Dale_K]

My 98 model temp light doesn't come on when I turn on the key.  I was thinking about ordering the alternative part mentioned in the thread until I got to the post that says the bike doesn't use a relay to turn on the light.  Made me think that even though the two parts look identical on the outside that they're not interchangeable but I'm a little confused.

Is the alternative part a genuine substitute?  Or should I look up the info on converting to the newer style system for the indicator?

[indybobm]

I did a poll years ago asking owners of 97-99 Standards and Tourers if the coolant light came on when the key was turned on. If I remember correctly, over 95% did not come on. I believe that the section of the Honda Service Manual is wrong concerning this. Maybe it works that way for the IS, I do not know. Do not expect it to come on when the key is turned on.

Dale_K, I do not think either is a relay. They are electronic modules that are designed for a certain model.

[MaverickValk]

The Temperature Indicator Unit is an electronic module. It takes the voltage reading from the Thero Unit on (#9) the thermostat housing and depending on the voltage (based on water temperature) decides when to turn on the coolant light.
Some cycle refitters do not not what it is and call it a fuel pump relay. It is not a relay.
There are similar units used on different models of Hondas but they are calibrated differently for that bike.
The Temperature Indicator Unit has nothing to do with turning on the fan. Proper operation of the fan is controlled by the Thermo Switch Assembly on the lower rear corner of the radiator. This switch can go bad and connection at the switch can get corroded. When the engine water temperature reaches 208 - 216 degrees, the switch turns on the fan until the temperature goes back down to below 199 - 207 degrees.

Thanks for the information.  Now I'm going to double check that thermo switch since I have a new one sitting right here.

Aaaaaand...  the Woo-Hoo has become a Boo-Hoo.  I was thinking since I didn't have an indicator light before replacing the part and I did have the light after installing it my problem had been solved.  After reading IndyBob's post I wasn't so sure.  Warmed it up, no fan joy.  Drained the antifreeze and installed a new thermo switch assembly, filled the radiator again and warmed it up.  TO A @#$& boil!    Damn, looks like thermostat will be next.  Then the water pump???

A water pump failure is normally a shaft seal (leaking) or a bad bearing (noise). I've never heard of a water pump fail to pump water properly as a failure mode. Just sayin'.

[Valkorado]

I grounded the switch, the fan does work.

First question, when you grounded the wire from the fan, did you ground it to the radiator or the bike frame? If the fan does not come on with the wire grounded to the radiator but does come on when you ground to the frame, then the radiator is not properly grounded to the frame.

If the fan comes on when you ground the wire to the Thermo Switch on the radiator but the fan does not come when the engine is hot, the Thermo Switch must be bad. Also remember that the fan gets its ground through the Thermo Switch and through the metal radiator.

Wow, is this ever maddening.  I got a new thermostat today, and installed it.  Didn't much enjoy getting to the back bolt on the thermostat housing, man was that ever a bitch to get to even with a wobble wrench.  But I digress.

So, with both the new thermo switch and the new thermostat installed, I started the bike and let it get to operating temperature.  NO fan.  Plus it looks like the radiator gets to come off again for an upper hose leak. Oh, boy!!!

I came back in and read your post.  Another friend mentioned it could be a bad ground, so before I started replacing stuff I tried a grounding wire from the radiator to the frame.  That didn't do anything.  But when I grounded the thermo switch wire to the bike crash bar the fan ran, so I knew it wasn't a bad fan motor.

So, just now I just ran a ground from the themo switch wire to the radiator and the fan starts up.  Then I ran the same wire from the thermo switch wire to the bike's crash bar and again the fan runs.  BUT when I run a wire directly from the (new) thermo switch to either the radiator or the frame the fan does not operate.

Where does the radiator normally ground to the bike?  I'm confused how I could have lost ground to the radiator.

What next?  I see there is a part Honda calls an Engine Coolant Temperature Sensor 36151-MT8-003 that attaches to the thermostat body.  The service manual lists it as a possible culprit after the thermo switch.

I am on a MISSION to get this overheating problem fixed.

[Valkorado]

A water pump failure is normally a shaft seal (leaking) or a bad bearing (noise). I've never heard of a water pump fail to pump water properly as a failure mode. Just sayin'.

Good!     One less thing to worry about!  This is really starting to drive me nuckin' futz!   

[indybobm]

If your engine is boiling over and the fan is not running, that is your problem.
There is nothing on the thermostat housing that has anything to do with turning the fan on when tbe engine gets hot enough. As long as the fan has 12vdc, it is strictly up to the Thermo Unit on the radiator to provide the ground that turns the fan on.
Next time the engine is hot and the fan should be running, leave the fan wire on the Thermo Unit and ground the body of the Thermo Unit. If the fan turns, then you have bad continuity between the threads of the Thermo Unit and the radiator.

[Valkorado]

Next time the engine is hot and the fan should be running, leave the fan wire on the Thermo Unit and ground the body of the Thermo Unit. If the fan turns, then you have bad continuity between the threads of the Thermo Unit and the radiator.

What would cause this, or better yet how would I solve it?  The OEM and likely original thermo unit is not triggering the fan, nor is the brand new one I just installed.  

Using a ground wire triggers the fan when grounded between the thermo unit and the radiator (as long as the thermo unit is plugged in) but it runs constantly that way.  

Thanks for your suggestions, BTW.

[Savago]

As a quick and dirty solution you could add a switch that would ground the sensor (therefore allowing to manually turn on the fan in case of need).

Do you have a water gauge or maybe one of those oil dip stick thermometers to monitor the engine temperature?

I was able to run my I/S for over one year with the radiator fan motor not working without ever boiling the engine water (had the warning light turning on twice when stuck in the traffic).