Someone elses problem

[Cautrell05]

Starting to think thats what I bought. 84 VT700c 29,000 all original, over heats. At idle its fine. driving along at 15+ its fine. after its warmed up if its left to idle the temp will keep climbing up into the red pretty consistently. The coolant is full. In the 150 miles I have put on it so far it has never leaked coolant or needed refiled. Radiator cap was tested at the bike shop yesterday. Its fine. I have good circulation below the radiator cap with the PRMs raised. I pulled the radiator and t-stat housing tonight. Couple things I noticed. The coolant is VERY green. Just changed green. The upper hose at the raditor and the lower hose at the water pump came off very easy like they had been off recently. I ran water through the radiator and it had real good flow in either direction and no buildup inside at all. The tubes i could see were clear. The inside of the t-stat housing was also very clean with 0 corosion or buildup. I did the stovetop pan/ cooking thermometer thing. T-stat started to open at 185 and by 205 it was open a full 3/8 inch.

The fan runs all the time. The switch measures open with a volt meter regardless of coolant temp. Previous owner installed a fuse inplace of the switch. The fan runs strong and pulls a noticable amount of hot air out of the radiator when its running.

Im at the point where I have no idea where to look next. Any help would be great. Thanks

Nick

[gordo2472003]

Oil level good? Check the spark plug maybe running to lean.maybe your temp switch is faulty? Just ideas

[jpr1968]

Don't trust your temp gauge, it could be faulty. Get a infrared thermometer and point at different parts of the cooling system and see what temps you actually see.

[rkforrest]

Sometimes the Gauges lie.

[tcanthonyii]

My guess the gauge as well.

[John Hopkins]

The switch that reads open is the first thing to change..

let's hope the waterpump is ok.

drain the coolant.

fill the radiator cap with new coolant until it reaches the neck..

rock the bike from side to side and watch for air bubbles, then refill..

leave the radiator cap off and run the engine..

rock the bike from side to side and watch for air bubbles, then refill.

put the radiator cap on and run the engine

leave the engine to cool and open the radiator cap top up again

Now you should have about 2 litres of coolant in the bike

look in the reserve tank and see the fluid level, you will need a flashlight for this..

the level should be up to the top mark.

look for leaks under the bike..

John.

[jimnfor]

Don't over think it, I think we have all done that at some point with our bikes.

[Dropkick_pride]

Originally Posted by Cautrell05

Starting to think thats what I bought. 84 VT700c 29,000 all original, over heats. At idle its fine. driving along at 15+ its fine. after its warmed up if its left to idle the temp will keep climbing up into the red pretty consistently. The coolant is full. In the 150 miles I have put on it so far it has never leaked coolant or needed refiled. Radiator cap was tested at the bike shop yesterday. Its fine. I have good circulation below the radiator cap with the PRMs raised. I pulled the radiator and t-stat housing tonight. Couple things I noticed. The coolant is VERY green. Just changed green. The upper hose at the raditor and the lower hose at the water pump came off very easy like they had been off recently. I ran water through the radiator and it had real good flow in either direction and no buildup inside at all. The tubes i could see were clear. The inside of the t-stat housing was also very clean with 0 corosion or buildup. I did the stovetop pan/ cooking thermometer thing. T-stat started to open at 185 and by 205 it was open a full 3/8 inch.

The fan runs all the time. The switch measures open with a volt meter regardless of coolant temp. Previous owner installed a fuse inplace of the switch. The fan runs strong and pulls a noticable amount of hot air out of the radiator when its running.

Im at the point where I have no idea where to look next. Any help would be great. Thanks

Nick

Looks the previous owner had issues with it as well... changed out the obvious parts... and even went as far as replacing the switch with a fuse to keep the fan running all the time....


You have two problems.... 1) the overheating and 2) the potential hack job(s) the previous owner did to try and fix --- or try and hide ? --- the issue.


Go through all the basics. Step by step from the simplest, to the most in depth you feel comfortable doing. If you dont find the problem take it to a professional and get the whole thing looked through.


Edit: plus look very closely at the rest of the bike for "repairs" that the previous owner(s) might have done.

[csmbt]

I am also fixing a "someone else's problem" bike and in my case the actual water pump impeller itself was shot and I needed to replace the pump

if you can pull the pump cover it's not a bad idea to check

also check your thermostat is actually working it may be bad

Maybe you have a blocked pipe somewhere too ... not out of the question

But as mentioned it is likely to be the gauge itself - infra red thermometer is the way to go for sure to see if it is even an issue

[Cautrell05]

Thanks for the imput guys. I figure the next step before putting it back together is to put the lower hose to the waterpump in a bucket of water and see how much flow I get out of each hose going to the t-stat housing while I have it off. After that I guess its put it back together and check resistance of the temp sensor while its warming up. I'm pretty sure there was a chart in the manual for resistance at different temps. This is extremelyfrustrating for me because my dayjob is a gm mechanic. Diaging problems on new cars is one thing but the cooling system on an 84 motorcycle should be stupid simple. Same parts, just smaller. Hopefully I can figure something out tonight.

Nick