Honda Shadow Forums banner
1 - 20 of 31 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter · #1 ·
Hi fellow riders,

I have an overheating issue with my Shadow 750 ACE ( 98 ) and I'm running out of ideas. Maybe I could get some pointers here.

Everything started with the overheating light turning on one evening while coming back from work in medium traffic. With the help of the manual, I discovered that the fan was not starting because the heat sensor was not working anymore. I went to the garage and explained the issue to the mechanic guy. The sensor was burnt and the guy changed it. The fan was starting again and I was happy.

Unfortunately, in the following week the overheating light lighted red again on my way to work. Being caught in traffic, I didn't really noticed because the light stopped as soon as I was able to gain speed. But as days passed, the light turned red sooner and sooner and it began to really worry me. I checked to cooler level and the fan twice, but nothing odd. Then I went back to the garage and the mechanic guy told me that my thermostat was stuck close. The guy changed it and the heat sensor. He told me that the coolant was flowing normally and that everything would be ok from now. I really hoped he would be right because it costed me a lot of money.

The next day, the red overheating light turned on again and for 4 days in a row, it turned on sooner and sooner to a point that it would turn red after 15min of riding. Sometime the traffic was heavy and I understand that a motorcycle can finally overheat, but 15 minutes is a very very short time, isn't it ?

I left my motorcycle parked at home since (it's been 6 weeks) to save enough money to bring it back to the garage. I just rode it 3 or 4 time around the neighborhood, but even without traffic, the motorcycle was way too hot for such a short ride.

Maybe some of you may have experienced such issues. I'd appreciate advices and pointers to understand what's happening because I begin to think that the issue may not be "not enough cooling" but "too much heating".

My motorcycle is a Shadow ACE VT750 from 1998 with 120000km on the odometer. I joined a picture of the bike to help identify the model if that can help.
(imgur: the simple image sharer)

Thank you for any help you could bring !
 

·
Registered
Joined
·
354 Posts
Thornska, overheating like you describe happens occasionally but what you and your mechanic have already covered all the usual things it could be, so I can't give you the magic answer but I'm sure someone here will. Coolant level good, fan operating and thermostat functioning? Is the fan running each time it has overheated? Radiator fins clean and in good condition? The coolant actually circulating through the system?
It only happens when stuck in traffic? That's gotta be air circulation.
My brother had a similar problem once so he connected a simple toggle switch across the fan's thermostatic switch terminals. He could manually energize the fan in emergencies like you describe. I'll shut up and give the others a chance to help. Good luck, looking forward to seeing this mystery solved.
 

·
Registered
2001 Valkyrie I/S
Joined
·
6,478 Posts
Well if your mechanic isn't ripping you off and really changed the thermostat and your fan is turning on when it should you might start with a new radiator cap. Normally when a waterpump goes it starts leaking so is there any antifreeze leaking anywhere? How is the fluid level in your expansion tank? Also may need to flush your radiator.
 

·
Registered
99' Valkyrie/North Central Indiana
Joined
·
9,575 Posts
As mentioned I would check to be sure the coolant tank is topped off @ cold/level. 75,000 mi. on a 16 yr. old bike, could be just a good coolant system cleaning and replacing coolant and the thermostat. Be sure to "burp" the system according to the OEM manual. If that don't work/help I'd say the waterpump would need to be replaced.
 

·
Registered
Joined
·
18,122 Posts
I cannot add what I was going to...Being as, it has already been suggested...;)

I well imagine, with what has been done, I`ve gotta ask was the coolant changed, and burped properly???
I sure hope your mechanic is trustworthy...

I wish I knew more,
D
 

·
Registered
Joined
·
4,076 Posts
I begin to think that the issue may not be "not enough cooling" but "too much heating".
Have you checked your oil level? Of course your water pump is working okay?


With the manual, I discovered that the fan was not starting because the heat sensor was not working anymore.
If by the "heat sensor" you mean the 'coolant temperature sensor' (not the thermostat), the sensor only lights up the dashboard warning light. The sensor isn't connected to the radiator fan in any way. They're on separate circuits. The thermostat exclusively triggers ON the radiator fan. True, the warning light should light up at the same moment the fan goes on, in unison, but the two units aren't daisy chained to each other electrically.

Just out of curiosity, did the mechanic replace the coolant temperature sensor twice?


Then I went back to the garage and the mechanic guy told me that my thermostat was stuck close. The guy changed it and the heat sensor.
  • He told me that the coolant was flowing normally and that everything would be ok from now.
I really hoped he would be right because it costed me a lot of money.
The thermostat has noting to do with the 'coolant flowing.' The last I checked, the waterpump operates continuously once the engine is running. The thermostat turns ON the radiator fan. The thermostat doesn't activate the water pump. Perhaps the confusion for this is that people mistake the bike's water pump for those type of water pumps that you plug into a wall outlet that's powered by electricity such that the thermostat serves as an On & Off switch.
 

·
Registered
Joined
·
354 Posts
Have you checked your oil level? Of course your water pump is working okay?




If by the "heat sensor" you mean the 'coolant temperature sensor' (not the thermostat), the sensor only lights up the dashboard warning light. The sensor isn't connected to the radiator fan in any way. They're on separate circuits. The thermostat exclusively triggers ON the radiator fan. True, the warning light should light up at the same moment the fan goes on, in unison, but the two units aren't daisy chained to each other electrically.

Just out of curiosity, did the mechanic replace the coolant temperature sensor twice?




The thermostat has noting to do with the 'coolant flowing.' The last I checked, the waterpump operates continuously once the engine is running. The thermostat turns ON the radiator fan. The thermostat doesn't activate the water pump. Perhaps the confusion for this is that people mistake the bike's water pump for those type of water pumps that you plug into a wall outlet that's powered by electricity such that the thermostat serves as an On & Off switch.

We gotta be careful here. There are three thermostats. A. Switch that operates the light. B. Switch that operates the fan. C. Thermostat that blocks water from the radiator until the engine is full operating temp.
Has anyone really had the misunderstanding that the water pump is switched? I didn't know.
 

·
Registered
Joined
·
4,076 Posts
We gotta be careful here. There are three thermostats. A. Switch that operates the light. B. Switch that operates the fan. C. Thermostat that blocks water from the radiator until the engine is full operating temp.
At least on the OP's ACE 750, there's only 2 thermostatic switches for the cooling system. The switch that operates the light (A, above), and the switch that operates the fan (B, above). So by my math, 2 switches.

There might be an additional switch on other engines as you state that temporarily stops the coolant from circulating until the engine reaches full operating temp. But are you sure on that? That would require shutting off the water pump which is questionable since the water pump is gear driven and runs continuously. That leaves looping the coolant around the radiator, instead of through it? I guess, possible. Anyways, in this instance, the thermostatic sensor isn't a valve, nor does it control a valve stationed in the coolant line.

Has anyone really had the misunderstanding that the water pump is switched? I didn't know.
Well, are there any electrical wires connected to the water pump to trigger the water pump OFF and ON?
 

·
Registered
Joined
·
354 Posts
I remember my Dad in 1962 took me to an auto supply to get our Buick a thermostat. Little thing that went into the manifold under the top radiator hose. He called it a thermostat. The word "THERMOSTAT" was offset printed onto the box. I got my first car. 1964 Fairlane 500. 289. It had an overheating problem. Turned out to be the THERMOSTAT. Exactly the same as the Buick. In the next four and a half decades I've replaced probably ten of them. In cars and liquid cooled motorcycles and other than the bike's THERMOSTATS being slightly smaller they were almost identical. Just like the one under the water neck of my Dodge Truck, Mazda Miata, Honda Goldwing, Ford Tractor, Mercruiser inboard, Honda Goldwing, VTX and Shadow. The motorcycles all have three thermostats Two of them are thermostatic switches and the third is a thermostatic valve. Come on guys. This dead horse is getting thrashed to ribbons. Two thermostatic switches, fan and indicator. One thermostatic valve.
 

·
Registered
Joined
·
4,076 Posts
  • Two thermostatic switches, fan and indicator.
  • One thermostatic valve.
Good to know. Duely noted. I owe you a drink. It's safe to say that *THERMOSTAT* usually means the valve thingie located under the radiator cap, instead of the senors for the fan & light. I've never had trouble with that thermostat.

This dead horse is getting thrashed to ribbons.
Really? Go easy on us now.
 

·
Premium Member
Joined
·
2,129 Posts
Replace the radiator pressure cap with a new one. Keep it simple!
 

·
Registered
Joined
·
208 Posts
What Beezer said.

Pull out the diagrams and read some. Idle to low, low circulation also throw that in the mix.
 

·
Registered
Joined
·
11,525 Posts
At least on the OP's ACE 750, there's only 2 thermostatic switches for the cooling system. The switch that operates the light (A, above), and the switch that operates the fan (B, above). So by my math, 2 switches.

There might be an additional switch on other engines as you state that temporarily stops the coolant from circulating until the engine reaches full operating temp. But are you sure on that? That would require shutting off the water pump which is questionable since the water pump is gear driven and runs continuously. That leaves looping the coolant around the radiator, instead of through it? I guess, possible. Anyways, in this instance, the thermostatic sensor isn't a valve, nor does it control a valve stationed in the coolant line.



Well, are there any electrical wires connected to the water pump to trigger the water pump OFF and ON?
The thermostat doesn't control the cooling fan. It keeps coolant from going to the radiator until it reaches operating temperature. It doesn't harm thee water pump at all. Cars, trucks, water cooled bikes all have thermostats that work the same way. The fan is controlled by a temp sensor that is in the bottom of the radiator. The third temp sensor is the one that goes to the over temp light and it's mounted in the cover for the thermostat.
 

·
Registered
Joined
·
4,076 Posts
The thermostat doesn't control the cooling fan. It keeps coolant from going to the radiator until it reaches operating temperature. It doesn't harm thee water pump at all. Cars, trucks, water cooled bikes all have thermostats that work the same way.
yes, I already said I owe Breezer a drink on that. No need to repeat. That 'thermostat' is the thing you boil in water to test it. I knew the test, but it slipped my mind. The differentiation is this thermostat is actually a valve, rather than a sensor like the other thermostat nomenclatures that gets thrown in the tossed salad.


Worth repeating the below ....
The fan is controlled by a temp sensor that is in the bottom of the radiator. The third temp sensor is the one that goes to the over temp light and it's mounted in the cover for the thermostat.
 

·
Registered
Joined
·
354 Posts
Oh hell, this wasn't an argument. This was a misunderstanding. Things like this happen a lot when the only way we have to communicate is typed responses.
For the record. I have never whipped a horse, dead or alive. I have beaten a horse with my fists though. I was a kid and my sister's horse stepped on my bare foot. And just stood there. I yelled and pounded the animal but it wouldn't move. That had a lot to do with my decision to NOT get a horse, but a motorcycle instead. I couldn't shift it, my foot was sore.
 

·
Premium Member
Joined
·
8,072 Posts
I thought all liquid cooled engines needed a thermostat bypass hose until the thermostat opened. Am I incorrect with this thinking.
 

·
Registered
Joined
·
18,122 Posts
I ain`t confused no more... ;)
Whew!!
Now that the word thermostat has been explained by the user...
Being a TV technician, I consider the temperature controlled switches = electrical switches, and the thermostat a valve which operates with temperature, opens at 170 degrees for example...

Ain`t the internet fun & confusing sometimes,
D


I repeat my question, has the coolant been changed and the system burped correctly??

Air causes problems when trapped inside the engine...
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #20 ·
Wow guys, thanks for so much replies ! The thing is I have close to 0 skill in mechanics, so I likely misused some words and I may not understand some things.

To sum up my situation in simpler, (and I hope) more accurate words :


  • The first time the warning temp light switched on, the fan was never starting.


  • I checked the fan by connecting it to the frame and it started


  • The mechanic changed the fan heat sensor and, according to his words, everything was working as expected.


  • During the following weeks, the warning temp light switched on again but would switch off as soon as I was able to gain speed.


  • Then, the warning temp light started to switched on more often, almost each trip to or from work. I ride twice 12.5 km in Paris to go to work, sometime with heavy traffic.


  • I went to a different mechanic and he told me that the thermostat (the thing you boil in water to test it) was stuck close, preventing the coolant to flow.


  • This guy changed the thermostat and one heat sensor that had melted. But I don't know if it was the fan heat sensor or the warning light heat sensor. The bill just says "contacteur thermique" (Google translates this to "thermal contactor").


  • According to the bill, the coolant was completely replaced. The mechanic said "the coolant is flowing as it is supposed to do" (but in french of course :p).


  • From this point, it went from bad to worse. The warning light switched on for each trip, sooner and sooner, and harder and harder to switch off by gaining speed. The last time I used my bike to get back from work, it switched on after no more than 15 minutes in traffic. I didn't think to check anything, I was too upset and worried to burn my engine.

Anyway, from what I read here, I should check for the water pump and the radiator cap. I have no ideas how to check those parts. Are there some easy checks that I can perform myself or should I go straight back to the mechanic ?

Again, thank you very much for your support and your replies. I don't feel alone anymore !
 
1 - 20 of 31 Posts
Top