Still overheating - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 12 (permalink) Old 04-13-2012, 04:19 AM Thread Starter
Steve
 
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Still overheating

I am absolutley stumped. My 86 VN750 is still overheating. I have changed the coolant at all locations, ie heads as well as water pump, and overflow, changed the thermostat for a new one, changed the Radiator cap for a new one. The overflow tank is full when hot and medium level when cool.

The only thing I can think is the water pump is stuffed. When I take off the radiator cap and rev the bike the level does drop down about half an inch and rises and when it returns to idle. Is that normal ?

Its still overheats into the red in traffic. I am using 10/40 oil. And 50/50 coolant (green)

I have also ran the bike for 10 minutes with the radiator cap off it and rocked it from side to side to remove any air bubbles. What else can I try ?

The bike goes really strong so iassume not a head gasket. There is no oil in the coolant, and visa v.

Steve

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post #2 of 12 (permalink) Old 04-13-2012, 05:13 AM
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Is your radiator fan coming on?

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
TOC MCCTs
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R


1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

2014 Honda VFR800F

1989 Pontiac Firebird Formula 350
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post #3 of 12 (permalink) Old 04-13-2012, 05:28 AM Thread Starter
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Yes the fan comes on when the temp is about half way or a little higher. It only stays on for about 15 seconds at a time. Is that too short ?

Steve

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post #4 of 12 (permalink) Old 04-13-2012, 05:34 AM
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Quote:
Originally Posted by 350ernie2 View Post
Yes the fan comes on when the temp is about half way or a little higher. It only stays on for about 15 seconds at a time. Is that too short ?
I've heard my fan run for much longer durations than that.

It's possible the fan is not running long enough, resulting in the heat you're describing.

As soon as you start moving again, does she cool right back off?

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
TOC MCCTs
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R


1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

2014 Honda VFR800F

1989 Pontiac Firebird Formula 350
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post #5 of 12 (permalink) Old 04-13-2012, 06:32 AM
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Is it possible that your sensor or gauge are simply not reading right ? If you think they are check your fan sensor in the bottom of the radiator ,ground the wire going to it and it should run constantly.if it still kicks off in a few seconds the fan relay may be dropping out.It is internal to the JB and can be by passed with an automotive relay externally.

I had to bypass mine on my750 with an external relay,after I bought Fan.To check it unplug it and run two wires straight from the battery and see if it runs constantly before bypassing the relay,I suspect either the sensor in the bottom of the radiator or the relay,but the temp sensor on the t-stat housing may be out of range causing a false reading on the gauge.




If you see it on my bike I did it
VROC#30324
92 vn750(sold)
Current ride 05 1500 Classic FI
lovin' the new scoot



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Click on one x and drag to the other to read between them.

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XI waited patiently for the Lord; and he turned unto me, and heard my cry. X
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post #6 of 12 (permalink) Old 04-13-2012, 08:49 AM Thread Starter
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I think the temp guauge is correct. Its a replacement (due to tach not working). Both have shown overheating.

I will try the the fan option tommorrow by grounding the wire. Which wire should I grounds BTW, and what is a JB ? Excuse my ignorance.

When I start moving the temp backs off after about 30 to 40 secs, but not much. Even at 100 km the temps is still just over half.

When I bought the bike the guy had water in it . No coolant. I have flushed it twice. There was some rusted iron bits in the overflow tank. Could these be stuck in the system somewhere casuing a blockage ? Its just a thought. I am just at a loss right now.

Steve

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post #7 of 12 (permalink) Old 04-13-2012, 09:35 AM
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Quote:
Originally Posted by 350ernie2 View Post
I think the temp guauge is correct. Its a replacement (due to tach not working). Both have shown overheating.

I will try the the fan option tommorrow by grounding the wire. Which wire should I grounds BTW, and what is a JB ? Excuse my ignorance.

When I start moving the temp backs off after about 30 to 40 secs, but not much. Even at 100 km the temps is still just over half.

When I bought the bike the guy had water in it . No coolant. I have flushed it twice. There was some rusted iron bits in the overflow tank. Could these be stuck in the system somewhere casuing a blockage ? Its just a thought. I am just at a loss right now.
about halfway on the gauge is about right ,running down the road.At the bottom of the radiator there is a sensor that makes up a ground to complete the circuit for the relay circuit,unplug that wire and ground it and turn the key on the fan should run constantly.If it does you have found the problem .If it doesn't and still kicks off it is the relay in the JB(Junction Box) or the fan motor,which is less likely.If the fan runs constantly with the wire I mentioned the fan sensor switch is bad (the one you unplugged the wire from).




If you see it on my bike I did it
VROC#30324
92 vn750(sold)
Current ride 05 1500 Classic FI
lovin' the new scoot



Quote:
"When all is said and done,usually more is said than done" UNK
Click on one x and drag to the other to read between them.

Psalm 40:1...
XI waited patiently for the Lord; and he turned unto me, and heard my cry. X
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post #8 of 12 (permalink) Old 04-13-2012, 06:57 PM
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Check your overflow cap seal too. Mine was a lil too warm once, and when I removed the overflow cap, idle went up and it cooled down. Turns out the system was a lil overfilled, but the overflow tank wasnt allowing the extra to overflow ! Make sure your coolant level is right in the overflow as well.



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post #9 of 12 (permalink) Old 04-13-2012, 08:24 PM Thread Starter
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Thnaks Denny. I did the test with wire and the radiator fan runs constantly. The fan sensor switch needs replacing. Can I ask how this is done ?

Steve

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post #10 of 12 (permalink) Old 04-13-2012, 08:38 PM
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Fan switch unscrews from rad, where you pulled the connector off of! Got one, PM me

04-3,200 miles bought July 2011 with 928 miles. Loaded with acessories to many to list here, see my albums for more details! I also make a custom tank bib specific for the 750 if anyone is interested, ck my albums for some pics.
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