Want to Replace Thermostat


Information and questions on GL1800 Goldwings (2001-Present)
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kenwantz
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Want to Replace Thermostat

Postby kenwantz » Sun Sep 25, 2016 1:57 pm



My 2003 Goldwing 1800 overheats. It has 27000 miles and has been regularly maintained, except for the air filter replacement. There are no signs of coolant leaks and the coolant is only two years old. So after checking around with other bikers on the various forums there are some who I think the problem may be the thermostat is staying open and needs replacing. Referring to the service manual, it doesn't look like a particularly easy task for the DYI'er. Says that the fuel tank, starter, and alternator all need to be removed to gain access to the water pump which contains the thermostat. My question is: has anyone done a DYI thermostat replacement and if so how difficult is the job? Is there a DYI instruction available out there? Any comments/suggestions would be appreciated. Thanks in advance for the help.



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gipsy42
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Re: Want to Replace Thermostat

Postby gipsy42 » Sun Sep 25, 2016 5:25 pm

kenwantz wrote:My 2003 Goldwing 1800 overheats. Referring to the service manual, it doesn't look like a particularly easy task for the DYI'er. Says that the fuel tank, starter, and alternator all need to be removed to gain access to the water pump which contains the thermostat. Thanks in advance for the help.

I'm thinking out loud, so no warraties implies, Ok?, that statement sounds to me like a joke, where is located the water pump, at rear of engine by the alternator, or on the right side by the starter??.
On the 1500 is located in front, under and very close to radiators right were it's supposed to be, and even whitout knowing the 1800 I can bet that just by removing the cowl you'll get access to it. Justa thought!
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702scottc
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Re: Want to Replace Thermostat

Postby 702scottc » Sun Sep 25, 2016 7:45 pm

Doesn't look like something you couldn't do. A good weekend project. I looked in my repair manual and removing the fuel tank is no big deal, just take your time. Once the tank is out remove the alternator and it's between the alternator and starter. You can probably get to the mounting bolts without removing the starter, but the alternator needs to be removed. I would recommend replacing the water pump and thermostat assy rather than just the thermostat, it's about $195 on bikebandit and I would bet the same thru cyclemax. For the amount of work involved to get to it just makes sense.
When exactly is your engine overheating? If the thermostat is stuck open it will usually run cooler at low speed and idle and heat up at highway speed. If it's stuck closed it will overheat all the time.

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themainviking
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Re: Want to Replace Thermostat

Postby themainviking » Mon Sep 26, 2016 6:36 am

Keep in mind that you are riding in a warm area. If your indication of overheating is the fan coming on occasionally, then perhaps you are not really overheating. I live in a much cooler climate than you do (most of the time, anyway) and after a days ride, when getting the bike ready to put away, my fans come on. This is at about 60 to 65 degrees F.
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kenwantz
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Re: Want to Replace Thermostat

Postby kenwantz » Mon Sep 26, 2016 7:43 am

Under normal conditions, i.e. near level riding, the temp gauge remains at normal level. But when riding upgrade or at slow speeds in lower gears, the temp gauge climbs and approaches near red line. Yesterday, the gauge hit the red line when the ambient temp was around 85F, but will cool down to normal gauge level (which is just south of mid-level) when stopped and idling.The fans are running when idling. I might question the accuracy of the gauge except I can feel the excessive heat and smell the overheating. Thanks for the suggestion, 702scottc, if I do go to the trouble of tearing the bike down, I agree I would definitely want to replace the water pump as well as the thermostat.

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702scottc
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Re: Want to Replace Thermostat

Postby 702scottc » Mon Sep 26, 2016 8:05 am

The way the fans operate are a bit unconventional, at speeds under 15 mph they run, over that the incoming air takes over. If you are tooling along in traffic around 20 mph the fans won't run and the engine will run warm. Once your speed drops the fans run and it cools down. I found this out when riding in California freeway traffic.lol.

kenwantz
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Re: Want to Replace Thermostat

Postby kenwantz » Mon Sep 26, 2016 8:27 am

702scottc, I understand that's how the fans operate. But what concerns me is that the temp doesn't just warm up, it pegs the red line. This just doesn't seem normal which lead me to think what could be the real problem here. My friend who was riding with me on a 1500 Goldwing doesn't experience the overheating. His gauge never rises above 1/2 way. Any thoughts?

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702scottc
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Re: Want to Replace Thermostat

Postby 702scottc » Mon Sep 26, 2016 9:49 am

The cooling fans and radiator placement on the 1500 is different, better actually. I have both bikes, 1500, 1800 and you would be hard pressed to overheat a 1500. I live in the hottest part of the US and rode all summer and my 1800 never got above 3/4 on gauge. It will heat up if you are moving around 25 mph just creeping, the fans won`t engage. Since the fans push air out the front of the bike on an 1800 vs drawing it thru the radiator like the 1500, the engine will run warmer but shouldn`t really overheat. I`m sure the engineers at Honda tested the cooling system on the 1800 rather vigorously before they sold the bikes, They have made them for many years now and its still the same setup. I have read where folks have rewired the motors run in the opposite direction and flipped the fan blades but you really shouldn`t have to do anything as long as the system is operating properly.
If your bike is heating up pulling hills and you are traveling at least 30 mph it definitely seems like the thermostat is stuck partially open. A bad radiator cap will cause issues as well along with running in to high a gear for the speed your are traveling.

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MikeB
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Re: Want to Replace Thermostat

Postby MikeB » Mon Sep 26, 2016 10:46 am

I can only assume that you have checked the quantity of fluid in the radiators as well as the fluid in the overflow because you do not say anything about it.

I have noticed that the 2001 thru 2005 all have the same heating issue. As stated above, the fans do not come on until you are at 15 mph or lower and this is for all generations of the GL1800 that I know of. At speeds below 25 mph or so, there is insufficient cooling air going through the radiators and the temp will climb. The 2006 and later GL1800's have larger radiators.

This August, my 2003 temp gauge was indicating above the red line and the needle was over the H on the gauge. That was due to a long uphill, behind a line of cars behind a large truck doing 20 mph on Lookout Pass going into Idaho. I was two up and pulling a cargo trailer. There were no pull offs and no way around. The ambient temp was 90 degrees Fahrenheit. There were two other wings in the group, a 2003 and a 2006. The other 2003, a single rider, experienced the same issue as mine. The 2006, which was riding two up, temperature climbed but the indicator only went to the line below the red line. We were only about 45 minutes from stopping for the night when this happened.

Later that evening, I checked the antifreeze and it was down in the radiators and the overflow was empty. Shocking since I had just replaced, burped, topped off and rechecked it two days earlier. Fluid had been up to the radiator cap and the overflow was showing fluid between the upper and lower marks on the dip stick at that time. Now, with the fluid down, I had to add a quart and a half to the radiator and then refill the overflow. There were no more issues with heating to that level.

I routinely see the needle climb on the temp indicator when in stop and go traffic when the temps are at 80 degrees or more. Once I exceed 30 to 40 mph, the needle will start back down. Yes, the temp will still climb but it is manageable with speed or stopping to let it idle and allowing the fans to run.

Changing your thermostat may help you but try not to be too disappointed when there is no change to the status quo.

The answer seems to be either install larger radiators or buy a newer, 2006 or later, GL1800.
MikeB
Tacoma, WA, USA

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Steve F
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Re: Want to Replace Thermostat

Postby Steve F » Mon Sep 26, 2016 11:39 am

Just an observation about you wanting to change the thermostat.... If it's stuck open, that would prevent the engine from reaching it's normal operating temp, not cause overheating. A stuck open thermostat is bad for the emissions settings in the ECU and may cause a fuel mixture problem.
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kenwantz
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Re: Want to Replace Thermostat

Postby kenwantz » Mon Sep 26, 2016 1:50 pm

Great explanations and suggestions. Happy to know my thermostat is probably operating normally and the overheating is temporary and manageable. I will get to the radiator, put on a new pressure cap and refill fluids, if needed. Thank you all and happy riding!

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702scottc
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Re: Want to Replace Thermostat

Postby 702scottc » Mon Sep 26, 2016 9:29 pm

Here is something you might want to try:

The ECM controls the fans by simply supplying a ground to the fan relay according to the wiring schematic. A simple secondary ground connected to a rocker switch mounted someplace easy to access would allow you to override the ecm control of the fans, say at any speed below 30 mph. Any faster than that would be of no value to run the fans, nor would you need them. The ECM would still control the fans under normal conditions with the switch off but this would allow you the option on those occasions when you are in traffic or pulling long grades at slow speeds. It would be prudent to install a diode ahead of the installed ground wire to avoid grounding the ECM circuit. The wire is easily accessed behind the relay panel so you wouldn't need to get to involved taking off any plastic.

Something to consider.

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Re: Want to Replace Thermostat

Postby MikeB » Mon Sep 26, 2016 9:49 pm

I'd be very interested to know if anybody has tried this yet. I'd like to know what they're experience was and if it actually helped or not. It sounds like a logical approach.
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Steve F
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Re: Want to Replace Thermostat

Postby Steve F » Tue Sep 27, 2016 6:31 am

MikeB wrote:I'd be very interested to know if anybody has tried this yet. I'd like to know what they're experience was and if it actually helped or not. It sounds like a logical approach.

Regarding the fans on a manual switch....A couple of potential issues I can see, 1) You forget to turn off the switch and proceed down the highway with the fans fighting the natural air flow.....you may overheat. 2) ---OR--- To have fans that aren't going to be fighting the normal air flow, others have reversed the fan blades on the motor shaft and then reversed the motor polarity to get the air to be blown out the sides instead of forward. NOTE: The fan blades are engineered to rotate in only one direction and are quite inefficient running in the wrong direction.
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702scottc
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Re: Want to Replace Thermostat

Postby 702scottc » Tue Sep 27, 2016 7:21 am

You are right, forgetting to turn them off would be an issue. A person would need to be mindful. I think it's an easy solution and it would correct the low speed overheating issue. I've read where folks have rewired the motors and flipped the blades, probably works ok but like you say the blades where not designed that way. A lot of work to get to.
Too bad Honda couldn't reflash the ECM to leave the fans run a bit longer, say 25 mph shutdown rather than 15 mph, this issue would disappear.

kenwantz
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Re: Want to Replace Thermostat

Postby kenwantz » Tue Sep 27, 2016 9:37 am

Considering the fan switch installation. If I were to do it, could someone please provide details how exactly this installation is done. I definitely would appreciate the help.




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