2002 VTX1800S - Overheating Issue

Tech Q&A for the VTX 1800 - PLEASE keep this section tech-oriented only!

2002 VTX1800S - Overheating Issue

Postby armyjag » Tue Jul 11, 2017 8:15 am

I was out riding with my son yesterday and the hot engine light came on going about 55 on the road we were riding. I stopped and the light went off, but as soon as started to ride shortly after going, it came on again. In addition, my son was riding behind me, said he seen coolant spray out the back end. Checked for hose cracks, and didn't see any.

Got it home and lifted the tank and took off the ECT Sensor from behind the radiator cap. The reason took this, was in one of the threads on this site, I believe you stated if the temp light does not come on for a second or two when you turn the key, this sensor may be done. In addition, after pulling it, it was dry as a bone. Coolant was low as well.

Did the grounding of the fan, it works.

Question is, do you think it is only the ECT Sensor or could the problem also be the sensor in the bottom of the radiator as well?

Any recommendations on where to get this part for the best price?

Any help to get my bike back on the road again is appreciated.
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Re: 2002 VTX1800S - Overheating Issue

Postby Bareass172 » Tue Jul 11, 2017 9:50 pm

Check your coolant reservoir - many will crack when hit with road debris. If reservoir goes dry, the cooling system will eventually do the same. Also check the lower radiator mounts as they are known to crack from metal fatigue over time. Often the rad can be fixed with a quick touch up weld if you have access to a welder. If not I know guys who have run it to a muffler shop and thrown $20 at one of the guys to run a bead.

I would not replace any sensor until you refill the coolant and run it again. Your sensor/light coming on in the conditions you describe are perfectly consistent with low coolant in the system. The coolant can overheat and when you blip the throttle or accelerate hard the water pump pushes fluid past the sensor, triggering the light. The sensor may be fine, the low coolant may be your entire issue. Just be sure you figure out the loss of coolant before you repeat the entire situation.

If it still persists, tell me the conditions afterwards, but I believe the sensors are acting as they should. ;)
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Re: 2002 VTX1800S - Overheating Issue

Postby armyjag » Sun Jul 16, 2017 9:06 pm

Checked the overflow tank for any cracks etc, nothing that we can see. Filled the bike with coolant, changed the oil while I was at it. Checked the lower radiator mounts and everything looked fine.

Took the bike out for a ride today - about 90 degrees, and within 5 miles the light came on again. Got it home and the fan was not running, and the overflow tank was still full.

Later we let the bike run in the driveway @ 97 degrees for awhile and the light came on again. Fan didn't turn on again.

Not sure what we should do next to try and resolve this issue.
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Re: 2002 VTX1800S - Overheating Issue

Postby Bareass172 » Tue Jul 18, 2017 8:44 pm

Given what you said, now I do agree that the lower sensor/switch must be bad. Unfortunately you'll have to drain the system again, but you'll need the parts Honda calls:
SWITCH ASSY., THERMO - #37760-MT2-003
O-RING (13.5X1.4) - #91307-PH7-660
It's just the switch and the O-ring that seals it.
If you hadn't taken the wire off/on to test it already I would have said to do that just to rule out corrosion. Bottom line, you tested the fan by grounding it and it worked, so that thermal switch is the only thing left that could be causing the problem.

Was the dash light at least constant on this time? It sounds like it was.
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Re: 2002 VTX1800S - Overheating Issue

Postby armyjag » Wed Jul 19, 2017 7:39 am

The dash light was on constantly when it was overheating. Should I be checking the Thermostat while I am at it to ensure that is not an issue as well?
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Re: 2002 VTX1800S - Overheating Issue

Postby Bareass172 » Thu Jul 20, 2017 10:31 pm

Honestly, the thermostat is likely fine but it's certainly something you could replace if you want to eliminate the problem once and for all. The OEM is kinda pricey for what it is, so I would probably do a quick google search and see if anyone ever found a cheaper alternative. There is a process to evaluate yours, the old remove it and put it in a pot of boiling water to see if it opens thing. If there is no cheaper alternative I'd consider trying it that way before I dropped $30-40 on a new OEM. The thermostat should start to open around 180 degrees and the little valve should move 8mm (about 1/3").

Let me know how it goes! ;)
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Re: 2002 VTX1800S - Overheating Issue

Postby armyjag » Fri Aug 04, 2017 5:51 pm

Changed the fan switch, checked the thermostat (works) and the bike still has the overheating light come on.

It is either the etc or water pump. Any recommendations where to go from here?
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Re: 2002 VTX1800S - Overheating Issue

Postby armyjag » Fri Aug 04, 2017 7:05 pm

ECT or water pump?


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Re: 2002 VTX1800S - Overheating Issue

Postby Bareass172 » Tue Aug 08, 2017 8:11 pm

Sorry it took me a few days to reply. At this point it must be one or the other. The ECT is directly responsible for the dash light, so it's definitely a culprit. I would pull the plug on it and make sure all the pins look clean and that it's not just a corrosion issue. To check the pump, check out this link:
viewtopic.php?f=144&t=2107

That's what you're looking for from the weephole under the bike, if it's leaking the instructions are attached in that link. I hope it helps!
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Re: 2002 VTX1800S - Overheating Issue

Postby armyjag » Wed Aug 16, 2017 7:40 am

Replaced the ECT thermal sensor, cleaned the connection, and found no indications of the water pump leaking. Started it up yesterday and let it idle to see if the overheating light came on. It didn't come on and the fan started up when the bike was warm. However, I started it again yesterday afternoon - around 6:20 pm and let it idle. This time, fan didn't come on and the overheating light came on. Rechecked the coolant and the overflow tank - all full.

For curiosity sake, contacted the local Honda dealership and posed the question to them in reference to the ECT and water pump. They stated the water pump may be leaking inside? Is that a possibility - doesn't sound right to me anyway.

Not sure where to go from here - any recommendations?

David
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Re: 2002 VTX1800S - Overheating Issue

Postby Bareass172 » Sat Aug 26, 2017 1:31 am

David,
Sorry for the really slow replies of late, I've been burning the candle at both ends with work.

So I have an idea, I'm embarrassed to say I didn't bring it up sooner, but it's been years since I saw this problem. The early model VTX's had a notorious problem with the radiator cap not working as intended. You could fix it by either replacement OR, if it's not too bad, you could scrub the cap with a toothbrush and some coolant. Scrub all over, under and around the spring and the little gasket/seal, etc. The caps used to have a nasty habit of sticking and preventing good flow through the system as well as back and forth to the reservoir. This would cause random overheating, collapsing of the upper radiator hose, and a "gurgling" sound from the bike after it was shut down. So you could try that, it sounds trivial but it can be an issue.

Last question - have you ever run anything other than coolant and distilled water in the system? I ask because that would cause scale buildup and possibly some blockages.

Outside of that, it's a tough call since there's not much else you haven't already gone over. I agree that the "internal leakage" thing is bullshit. Pumps like this have some internal "slip" built into the design because the pump is not 100% efficient, but that's designed and expected. Any "leakage" you'd see at the weephole, that's what it's for.
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Re: 2002 VTX1800S - Overheating Issue

Postby armyjag » Sat Aug 26, 2017 12:14 pm

I will clean the cap good and see what happens. I had noticed it gurgling a couple times after shutting it down. I haven't ran anything other than coolant and distilled water. I had the motor rebuilt several years ago, wouldn't know what went through it prior to my purchasing it from the previous owner.

One thing I did notice is that the bottom radiator hose is much cooler than the top after running it for awhile. Not sure if that is an issue or not.


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Re: 2002 VTX1800S - Overheating Issue

Postby Bareass172 » Sat Aug 26, 2017 8:45 pm

If it's run good until now and you've always run the right coolant mix then I see no reason to question that further. It was just a thought as it's actually a problem I fought on my Jeep a few years back.
Your lower rad hose should be cooler as the flow is hot in the top, cooled out the bottom. The temperature variant should be noticeably different if everything is functioning well. The cap should only control flow between the reservoir and the cooling system, but when it's screwed up it can cause issues. I hope it's that simple because at this point I feel as if we're chasing the problem...
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Re: 2002 VTX1800S - Overheating Issue

Postby Super 8 » Sat Aug 26, 2017 10:13 pm

May want to try a new cap to get rid of the gurgling. I hope you did a complete flush and fill of the anti freeze.
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Re: 2002 VTX1800S - Overheating Issue

Postby armyjag » Tue Sep 05, 2017 11:11 am

I went out a rode the bike for several days in cool temperatures, and didn't have the overheat light come on at all. However, on Saturday temps were in the upper 80s/lower 90s. I took it out for a ride and the light came on a couple different times. First time was when I was riding at a steady 50-55 mph, it went off after a couple minutes. The second time was close to home and when the light came on, it didn't turn off.

So I decided to drain and flush the system yesterday. When I took out the bolt on the lower 5 o'clock position on the water pump, I expected a gush to run out of the hole. However, it was a very slow dripping of the coolant out of the system. What really amazed me was the upper bolt in the picture behind the wire, as soon as I loosened it, the flow would increase, but not by much. I finally got the system drained and flushed with Distilled water, as well as flushing the radiator directly really good and let it flush out of the bottom where the sensor was. I did not refill the system, because something tells me the slow dripping of the coolant from the bolt hole in the water pump doesn't look right. Not sure if there may be a potential issue or not. Could there be some buildup in the system?

Also checked for any cracks etc on the radiator which did not find any.

Looking for some advice going forward. This problem is becoming very frustrating.


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Short Video:
http://www.dabecker.com/pictures/vtx1800s/waterpump.mov
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Re: 2002 VTX1800S - Overheating Issue

Postby Bareass172 » Tue Sep 05, 2017 9:04 pm

The slow drip from that drain hole is normal and infuriating (I did watch the video to be sure). It is the reason I don't use it as a drain, I remove the lower radiator hose and drain it that way. That is a tiny hole to drain the system, and it's like holding your finger over a drinking straw - the liquid stays put or very slowly drains out as air can get in. Even if you remove the radiator cap, there are still restrictions that slow it down. Dropping the lower radiator hose speeds the entire process along, it just makes it a little harder to flush both ways through the system.
The remaining bolts aside from the drain hold the pump together (it's a split housing) so loosening the other bolt you mention is likely allowing air to seep in through the outside of the case and making it flow a little faster.

So I can completely appreciate and relate to your frustration trying to solve this problem. In that spirit I'm beginning to think maybe we should look at this from another angle. At this point, you've gone over almost everything in the system with the same problem. Is there any chance something else on the bike could have changed to cause the bike to run hotter than usual? Maybe the overheating is being caused by something else. I remember in previous posts we discussed that the bike used to have a fuel manager - have you installed another one or is the bike without? I ask because if the bike were lean it would run hot, and I've seen many times over the years where a fuel manager will lose it's map. It's just a thought, looking at this from a different perspective. Have you done anything else prior to this which might be related enough to cause the issue? Did you fool with the cap? I wish I could give you the answer to solve this, but if I were in your shoes I'd be doing everything you're doing and I've been working on these bikes 15 years. :huh:
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Re: 2002 VTX1800S - Overheating Issue

Postby armyjag » Tue Sep 05, 2017 9:13 pm

I did clean the radiator cap as you stated. I have not put a fuel manager back on the bike. The only other thing I did was put the plates on that I ordered from you to finish out the desmog process.

Makes sense that the hole would flow a bit faster when losses other bolt - it was a long process. Gave me time to do some other things around the garage.

In your opinion, would a radiator cap be an item to try just on the off chance it may be the problem?

I appreciate all the advice as always.


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Re: 2002 VTX1800S - Overheating Issue

Postby Bareass172 » Fri Sep 08, 2017 12:34 am

There are plenty of good condition used caps on ebay for really cheap, so it can't hurt to try it. In truth, I'm not seeing that as the cause of your problems at this point but we're nitpicking things before we have to start looking at other causes so I think it's worthwhile.
Other questions... When you checked, drained, and flushed the system, did you check to see how easily you had flow through the radiator and the engine? When you bled the system did you do it at the radiator cap? If so, did you see that you had good flow through the system once the thermostat opened? I'm curious to establish if the system is functioning as intended, because now I'm beginning to wonder if you have another contributing issue. I'm a big believer that the simplest solution is usually the right one, but we're narrowing this down one item at a time and still no solution so...

Let me know and we'll work from there.
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Re: 2002 VTX1800S - Overheating Issue

Postby Super 8 » Mon Sep 11, 2017 8:21 am

I don't remember mine flowing out of the drain that slow but I did have the cap off.
Here is a video of a how to and it's flowing out quite well.
https://www.youtube.com/watch?v=Ryi6cXfwhBM
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Re: 2002 VTX1800S - Overheating Issue

Postby Bareass172 » Mon Sep 11, 2017 9:34 pm

Holy hell! That has got to be under pressure! Never in my life have I seen the coolant do more than dribble out of these bikes. They do make pressure caps you can use to test a coolant system for a leak. My guess is they used something like that to put pressure behind the coolant, because that's downright comical how fast that comes spraying out.
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