I took a ride on my 2003 ST1300a this morning from my house at 6000 ft elevation, down to the valley at 4500 ft elevation, up to a mountain peak at 9000 ft elevation, back to the valley, and then home again. Outside temperatures started in the 70s at my house, 80s in the valley, and mid 60s at the mountain top. During the ride down to the valley, my engine temperature gauge showed 3 blocks out of 6 total. It went to 4 blocks waiting for a traffic light in the valley. As I climbed up to the 9000 ft peak, it fluctuated between 4 and 5 blocks. It dropped to 3 again heading down the mountain on my way back, and was 4 again in the valley. On the final run up the hill to my house, the outside temperature increased to 90 degrees. The engine temperature stayed at 4 blocks until the last 5 miles of uphill twisties where I rode more aggressively and the temperature gauge stayed at 5 blocks for most of the uphill. Are these temperatures reasonable? I rode the same ride in the opposite direction a few weeks ago and was at 5 blocks for almost all of the uphill sections. I thought that was high, so I checked my coolant level when I got home and found it was low. I added coolant before today's ride. I'm wondering if low coolant was my only problem or if I need to look for more cooling issues. Thanks for any insight you can offer.
Acceptable Engine Temps when Climbing Mountains
- Thread starter devitotl
- Start date
drrod
Site Supporter
Low coolant may have been the only issue but to be safe I would say your cooling system needs to be checked and/or serviced. A good flush, maybe a new thermostat, and ensure the fans are working for a start. A proper functioning cooling system should remain stable (3 bars) through all of the rides you describe. As a note....I have ridden mine in very similar conditions, including traffic in Palm Springs where the ambient temp was over 110 F, and the bike never went above 3 bars. Up and over many high passes in CO and the temp never budged.
I’ve never seen the temp indicator go above 3 bars. My A6 used to get ‘tired’ in the hot summer climbs in the Pyrenees and Picos in Spain.The engine started to feel ‘tight’, which is not a diagnosis but my imagination thinking what was wrong. The pre-2008 models used to run weak, and pinking lightly was common under load and at higher altitudes. It was mentioned in the handbook manual. A brief rest to let it cool and all was well again. I found that higher octane fuel, and quality fully synthetic oil stopped it from doing it - but I’d done over 30k miles before I found that cure - so maybe it was just run in.
You are LOW on coolant and probably have air in the system. Take the cap off the radiator and make sure it is topped off running out full. I would even leave the rad cap off and run it with it tilted slightly with the rad cap high to purge it of air bubbles. Be sure the coolant is circulating in the rad. Close it up then make sure the overflow bottle is up to the max line. ST1300's can have small leaks on top of the engine that can be overlooked for years (without problems in my opinion) but you have to keep the overflow full.
Try filling the rad then ride again and see what happens.
Mine never went above 3 bars that I can recall.
Try filling the rad then ride again and see what happens.
Mine never went above 3 bars that I can recall.
Sadlsor
Site Supporter
I can't say I recall ever seeing mine go above 3 bars.
2008 ST1300A.
2008 ST1300A.
Thanks to everyone for the insights. It looks like I still have some work to do.
Andrew Shadow
Site Supporter
The ST1300 cooling system capacity exceeds what the engine needs. I always figured that it was to accomodate the police duty versions that are operated under severe conditions. If your temperature gauge hits four bars and beyond something is wrong.
The only time my 1300's temp gauge showed anything other than 3 bars was when the thermostat began sticking. At first, it took longer than the 1 - 2 mile run up the street to hit 3 bars (after my driveway warmup to 1 bar). Later it overheated on a hot day on the ride returning home after a 75 mile ride with no indications of trouble. Scratches on the stat's center post, Larry said, were indicative of failure.
Here's a related question. Do I need to take the front fairings off to get to the radiator cap? It looks like it might be possible to gain access if I just remove the right hand glove box.
Few weeks ago i was driving in the Dolomites in Italië. With passenger and trailer behind the st1300. Temperature above 90 degrees fahrenheit. Or 34 degrees Celsius. It always stays on three Blocks. Cooling is Great.
But only if everything is in good condition and serviced.
But only if everything is in good condition and serviced.
If you could take the right glove box out, you should be able to reach the radiator cap, but I don't think you can take it out alone. I think you need to take the right side panel off.
Sadlsor
Site Supporter
That's how I've always done it, but note... that is not the same thing as telling you it's the only way, or the best way.
I always took the fairing apart. While you can probably get the cap off without taking everything apart, you won't be able to check the right side of the engine for coolant tracks (blue/green deposits on the side of the engine near the square and round drain holes). Too, adding coolant if necessary will be dicey. While you are in there (fairing off) its a good idea to eyeball the hose clamps. To get to the thermostat, if necessary, you will have to remove the radiator (after undoing the fan's electrical connectors using a tiny screwdriver and removing the fastening screws, pull the bottom of the radiator forward as you lift it up off the top hooks. Then remove the frame cross brace in front of the thermostat housing*. Don't just try to pull it forward without that tilt.
The hose going from the radiator cap's fitting to the overflow bottle is notorious for splitting on older bikes. Be sure to check this too for leaks.
*You can also reach the 'stat housing from above - by removing the gas tank, air filter housing, etc.
I would recommand to take the fairings off and flush the old cooling fluid out with a water hose.
I am also not a fan of the Honda green cooling fluid. You can better fill it with the pink G12+ cooling fluid. Brand is not importand.
That will increase the cooling power.
And check or replace the thermostat.
I am also not a fan of the Honda green cooling fluid. You can better fill it with the pink G12+ cooling fluid. Brand is not importand.
That will increase the cooling power.
And check or replace the thermostat.
Andrew Shadow
Site Supporter
Starting with G12++ and now G13 these coolants contains a small measure of silicate. I don't know what that means insofar as whether or not that is a concern for engines where the manufacturer has specified the use of silicate free coolant. Might be a matter of how much is to much. Where is that line? I have no idea.
Last edited:
Do not forget that our motors are 20+ years old and that this was not on the market. Myself and others also use full synthetic oil. Also not recommanded by Honda.
Andrew Shadow
Site Supporter
Exactly the point. G12++ and G13 might be fine for vehicles with newer technology and composite metals. Are they good for metal compositions used in 20 + year old vehicles. I don't know.
It is my understanding that Honda says no silicates. you can either go with zero or roll the dice. It's only a water pump that silicates mess with...
If the G12 coolant is glycol based, I doubt it will increase the cooling power. If it is a synthetic coolant, like what @Uncle Phil uses, then it might. However, the cooling system is designed to handle more heat than the engine normally throws off, so an increase in cooling power is not needed.
Thats why G12+ and not ++
It is complely backwards compatible and mixable with pink, blue and green cooling liquids.
It is an OAD liquid. Organic Acid Technologiy
And the base is Mono Ethyleen Glycol
It can NOT be mixed with a synthetic cooling fluid.
It is complely backwards compatible and mixable with pink, blue and green cooling liquids.
It is an OAD liquid. Organic Acid Technologiy
And the base is Mono Ethyleen Glycol
It can NOT be mixed with a synthetic cooling fluid.
Thanks for all of your help. I took the fairings off and saw the radiator was low on coolant. I topped it off, burped it, confirmed the overflow bottle was full, and took it for a ride up and down the same mountain passes. This time the heat only rose to 3 bars, so that worked great. However, I was inspecting the bike when I got it home and noticed it weeping from the water pump inspection hole and looks like it has been weeping from there for quite some time. The Honda service manual says I need to replace the water pump. Do you agree? If so, can you offer any tips? Also, I'll eventually need to put the fairing back on. Do you have any tips for that other than assembly is the reverse of removal?