Sticking Thermostat?

[bkuhr]

83VR STD

On cold start, warms up at idle or cruise until temp on gauge reads right at red/green line. Fan also comes on at red/green line, even at 50degF. Then suddenly starts to cool down to about 3/4 middle green. Then starts to rise all the way back to the red/green line. Does this cycle apx 3-4 times until finally cools to just above 1/2 middle green. Then it stays here rest of cruise, unless stopped in traffic, where it climbes back to red/green, fan cools to about 3/4, and cruising again cools to 1/2.

 

Thinking thermostat sticking when cold, and takes over high temp to get it to open.

 

Opionions?

[Rocket]

83VR STD

On cold start, warms up at idle or cruise until temp on gauge reads right at red/green line. Fan also comes on at red/green line, even at 50degF. Then suddenly starts to cool down to about 3/4 middle green. Then starts to rise all the way back to the red/green line. Does this cycle apx 3-4 times until finally cools to just above 1/2 middle green. Then it stays here rest of cruise, unless stopped in traffic, where it climbes back to red/green, fan cools to about 3/4, and cruising again cools to 1/2.

 

Thinking thermostat sticking when cold, and takes over high temp to get it to open.

 

Opionions?

 

Possible on thermostat, but fan operation is about normal, only kicks in when stopped.

There has been mention before, about guage calibration possibly being off.

[Dano]

There is a knob on the front of the engine, it's black and sits between the header pipes. Look at it closely, "off" should be at the 2 o'clock position. That's the drain valve. Check the coolant reservoir inside the right fairing making sure it's up to the line. You could also get a cheap infrared temperature gauge and check the temps at the thermostat.

[Venturous Randy]

There is a knob on the front of the engine, it's black and sits between the header pipes. Look at it closely, "off" should be at the 2 o'clock position. That's the drain valve. Check the coolant reservoir inside the right fairing making sure it's up to the line. You could also get a cheap infrared temperature gauge and check the temps at the thermostat.

 

To add to this, you may want to turn it to the open position and see what it does. This will by-pass the thermostat and should warm up much slower. I would not leave it in that position, but you could see what it does and it won't hurt anything. Down side is turning it may get it to develop an occasional leak and you will need to change the o'ring. You may have to loosen the screw in the side to get it to move.

RandyA

[bkuhr]

Thanks for all replies, aware of bypass-even has new o-ring, have not tried to run with bypass open, but once this calm down I seem to run just above 1/2 of green scale-seems about right. Coolant tank at 1/2 low and full. Fan appears to be working at correct temp-just at red, (BUT does fan actually help with cooling if thermostat is closed and no/limited flow thru radaitor)

 

Question is, is it normal for temp to run all the way up to the red? I am thinking the thermostat is sticking when opening, but when it gets open everything is as it should be.

Should thermostat be replaced? If so with what? OEM/auto(type?)

[Condor]

 

Question is, is it normal for temp to run all the way up to the red? I am thinking the thermostat is sticking when opening, but when it gets open everything is as it should be.

Should thermostat be replaced? If so with what? OEM/auto(type?)

 

When runing down the road the temp is very dependant on the air temp. It's not unusual for the guage to register in the mid-range at 50° ambient temperature and run close to the red in the high 90's to 100°+. while riding. At idle it -is- unusual to have the temp guage fluctuate up and down several times. I have seen this happen when a thermostat is installed backwards. It could also indicate a bad thermostat.

[skydoc_17]

I would defiantly check the overflow bottle and make sure you have coolant in there. I am thinking that after 27 years your thermostat has seen it's better day. Yamaha makes a very high quality, long life thermostat. Basically, it costs you $1.33 a YEAR for the last thermostat. Since it is a project to get to it and replace it, I would spend the extra money and put one in there that was going to last another 27 years myself. When I did mine I also ordered the thermostat housing cover, unlike the housing itself the cover is plastic and I have seen the cover leak AFTER the replacement of the thermostat. Because this is a messy, time consuming job, I put as many new parts in as my budget would allow. My thinking was, If I never have to remove this new thermostat again, that would be fine with me. I have a very nice down loadable instructional file of the removal/install with pics, I can also help with parts.

Earl

[GaryZ]

I have been riding my VR around without the fairing for the last couple of months. This means I have no over-flow tank and she spits out a little water each time I shut her down. When low on water she will run right up to red and then drop to normal (mid-gauge). In traffic she will cycle to red line and back to mid-gauge. Shortly after the cycling, she boils over. I would check your coolant level in the radiator and top off the overflow tank before changing the thermostat.

[capn eddie]

my 87 was doing this two months ago and i replaced the fan switch with the vmax switch that turns on at a lower temp. and changed the raditor cap and now it run at the middle of the green. i would start with replaceing the cap first since it is the chepest to do , i used a cap i got at napa.

[bkuhr]

Thanks all,

Before post had checked overflow tank, was and is at 1/2 between full and low mark.

This weekend pulled rad cap, stuck finger in hole:whistling:, and came up dry. Added about 1/4 gallon water. Not sure capacity, but 1/4 gallon in little tiny radiator was probably a lot!

 

This am rode and forgot to watch gauge as it warmed, but when I did look I was at middle green, and it stayed there for entire trip-even at stop.

 

Now I suspect due to having water in overflow tank, but not being drawn into low radiator during cooldown, that I have defective pressure cap. I think I need to replace it.

Does autoparts carry usable cap, or need OEM specific? BTW-83VS1200

[capn eddie]

Thanks all,

Before post had checked overflow tank, was and is at 1/2 between full and low mark.

This weekend pulled rad cap, stuck finger in hole:whistling:, and came up dry. Added about 1/4 gallon water. Not sure capacity, but 1/4 gallon in little tiny radiator was probably a lot!

 

This am rode and forgot to watch gauge as it warmed, but when I did look I was at middle green, and it stayed there for entire trip-even at stop.

 

Now I suspect due to having water in overflow tank, but not being drawn into low radiator during cooldown, that I have defective pressure cap. I think I need to replace it.

Does autoparts carry usable cap, or need OEM specific? BTW-83VS1200

 

I used one from autozone cst7513 is the one i bought but you can also use napa#bk7032443 or a stant #10227

[skydoc_17]

Hey Brian,

Take a GOOD CLOSE LOOK at the tube thar runs from the side of the overflow tank down to the nipple at the top of the Radiator. The tube gets crushed and plugged, the nipple on the overflow tank gets plugged, and this will keep the coolant from returning to the Radiator. When I got the 87'VR, I pulled the overflow tank, cleaned it good, and replaced the tube, (auto parts store, $1.00 a foot) and had no problems after that. Boy, was it clogged up. To get to the overflow tank, remove the Allen Head Cap Screws on the top of the fairing and it will expose the tank. Be sure NOT to overtighten those Cap Screws when you put it back together.

Earl

[GaryZ]

Hey Brian,

Take a GOOD CLOSE LOOK at the tube thar runs from the side of the overflow tank down to the nipple at the top of the Radiator. The tube gets crushed and plugged, the nipple on the overflow tank gets plugged, and this will keep the coolant from returning to the Radiator. When I got the 87'VR, I pulled the overflow tank, cleaned it good, and replaced the tube, (auto parts store, $1.00 a foot) and had no problems after that. Boy, was it clogged up. To get to the overflow tank, remove the Allen Head Cap Screws on the top of the fairing and it will expose the tank. Be sure NOT to overtighten those Cap Screws when you put it back together.

Earl

 

Today I replaced my radiator cap and discovered a simple way to check the hose from the overflow tank to the radiator. My MK1 overflow tank is physically higher than the radiator cap. If there is fluid in my overflow tank and the hose is not clogged, the tank will drain out the radiator cap when it is removed!

[bkuhr]

Today I replaced my radiator cap and discovered a simple way to check the hose from the overflow tank to the radiator. My MK1 overflow tank is physically higher than the radiator cap. If there is fluid in my overflow tank and the hose is not clogged, the tank will drain out the radiator cap when it is removed!

 

Good info, yesterday on way home stopped and picked up,

 

I used one from autozone cst7513

, fits great-thanks,

 

When I stopped at autoparts, Radiator was leaking from old cap, guess I didn't get it tight when I did the previous "finger test"

 

Radiator was hot-ie:full, even though I had lost fluid during leak, and overflow tank had not moved from previous position. Also per garyZ my tank did not drain. I topped off overflow with premix from autoparts and headed home. Guess tonight will check for overflow blockage, but temp gauge is doing great.

 

Ain't this a GREAT site:thumbsup2:

[jasonm.]

To add to this, you may want to turn it to the open position and see what it does. This will by-pass the thermostat and should warm up much slower. I would not leave it in that position, but you could see what it does and it won't hurt anything. Down side is turning it may get it to develop an occasional leak and you will need to change the o'ring. You may have to loosen the screw in the side to get it to move.

RandyA

The Yamaha manual makes no mention of loosening the small phillips screw by the drain.You should not have to loosen the screw. That screw is strictly an alignment screw to keep the valve from popping out and set at the correct depth. If you have to loosen the screw...then it's not the original.

Edited September 21, 2010 by jasonm.

[bkuhr]

Disconnected overflow hose at radiator, just a drop of antifreeze. Hooked up Mighty Vac to end of hose, just a couple of pumps and flowing. Disconnected Mighty Vac and entire overflow tank started draining by gravity-Just like GaryZ said. Put it all back together and hosed the mess off the scoot and the floor, and refilled overflow tank!

 

Able to complete all with just long curved nosed pliers, and didn't have to remove any plastic:)

 

Thank You all for input!

[jasonm.]

that's they way...good job

[N7228]

Sorry to intrude on this thread, but from what I read, I think you guys just stopped me from screwing up mine. I just need to confirm before I put my plug back in with new O-ring........That the screw actaully sits in the groove and allows the plug to spin all the way arround. The spring with a bearing sits in the small hole on the underside of the tube when it is RUN posission. Are both these statements correct?

 

(Didn't see any ball bearing when it came out - only the spring - and I was about to reinstall the plug so that the screw fit into the hole where the spring is located. Yeah, I know...... should have checked here before I decided to fix the drip.)

 

Roger

[bkuhr]

Sorry to intrude on this thread, but from what I read, I think you guys just stopped me from screwing up mine. I just need to confirm before I put my plug back in with new O-ring........That the screw actaully sits in the groove and allows the plug to spin all the way arround. The spring with a bearing sits in the small hole on the underside of the tube when it is RUN posission. Are both these statements correct?

 

(Didn't see any ball bearing when it came out - only the spring - and I was about to reinstall the plug so that the screw fit into the hole where the spring is located. Yeah, I know...... should have checked here before I decided to fix the drip.)

 

Roger

 

You are correct if talking about the bypass valve down low center. the screw goes in the slot and the valve can still turn, the spring presses on the missing ball bearing, and the bearing feels the detents (2 holes top and bottom) in the pipe. Normal is with writing upside down, and valve in detent. Guessing but about any ballbearing of about 1/4 inch diameter should work.

[skydoc_17]

Hey Roger,

You can use a 5MM or 5/32" Ball bearing to replace the missing ball from the radiator drain.

Just an FYI.

Earl

[Snaggletooth]

Once you get that cleaned up and back together you will feel the detent much better. Remember that the "OFF" goes to the 2 o'clock position for normal running and the "ON" goes to the 2 o'clock position to drain the system.

[N7228]

Thanks !!!!!! Once I knew what to look for I went back to the shop and, after some tedious crawling around on the floor and a few bumps to the head, I found the missing ball bearing. I got the assembly put back together. Bearing is in the down position (bottom hole) and writing is upside down and at the 2:00 o'clock. (with the tops of the letters at 5:00 c"clock) I appreciate your help & advise. Filled the radiator and the reservoir (spelling?) and placed a clean paper towel under the drain plug to check for drips after it sits all night. So far - so good.

 

Thanks

Roger