700 red head over heating

yamyrider

yamyrider

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Northern Ontario
700 red head impeller was shattered from the bolt comming lose. installed new impeller with locktight. Bled the coolant very well. If you ride over 7000 rpm all is fine. When riding in lower rpms the temp light come on and she gets hot. Checked for head leaked, base gasket all is fine. not burning coolant. At a lose what to look for. motor is stock..no mods at all
 

Is she really getting hot,did you stop ASAP and feel the heads/cyls,coolers???

with cap off can you see coolant circulating?
 
it was boiling over..the overflow cap blew off it was sooooo hot. But if I manage to stay over the 7000rpm the light will go out and she will cool down.
 
yamyrider said:
700 red head impeller was shattered from the bolt comming lose. installed new impeller with locktight. Bled the coolant very well. If you ride over 7000 rpm all is fine. When riding in lower rpms the temp light come on and she gets hot. Checked for head leaked, base gasket all is fine. not burning coolant. At a lose what to look for. motor is stock..no mods at all
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could it be that there are pieces of the old impeller lodged some where in the cooling system causing a restriction but at 7000rpm and above the pump can create enuf flo to cool things off.
 
we pressure washed the coolant system for 6 minutes...inserted the pressure washer at one end and let it run for 6 minutes through entire system. It is really not possible to pieces of the impeller to flow through the system. It would have to be a very small piece to work its way up the cylinder coolant ports.
 
If the original over heating got hot enough to warp the head, you can be getting some compression air getting into the cooling system, this will exceed to pressure for the cooling system cap and overflow. Remove the cap and check for water flow and air bubbles. Al
 
when checking the flow there are air bubbles at first...then after hitting the throttle to increase rpm the fluid flows very well. If you close the cap and ride until the light come on, wait for the sled to cool a little and remove the cap there will be some air bubbles again. If it were the heads the motor would be burning coolant?
 
If it were the heads the motor would be burning coolant?
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not nessicarily, i just had a 454 last summer that had a head gasket leak, never lost a drop of coolant into the engine, it would pressurize the cooling system from the cylinder pressure, i realize this is a sled not a car youre dealing with, but it is possible
 
Im thinkin' your locktite wasn't tight enough. New impeller loose and just floatin in the fluid? You gotta see fluid flow at all RPMs. No restrictions and no flow means no impeller (or no fluid but that would be obvious).
 
mustangzrule said:
Im thinkin' your locktite wasn't tight enough. New impeller loose and just floatin in the fluid? You gotta see fluid flow at all RPMs. No restrictions and no flow means no impeller (or no fluid but that would be obvious).
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Nope..took the water pump cover back off the check the impeller. You cant hold the impeller if someone turns the clutch...the locktite is holding very well.
Two of us tried holding the impeller while the clutch was being turned and you cant stop the impeller from spinning
 
I'll bet head warpage, put a flat edge on it and see.

might not hurt gasket right away, making checking gasket area for cracks stuff no good.
 
no1chevyboy said:
did you (back) flush the system? hoses on correct? are heat exchangers hot? bleed the system?
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bacl flush.???????..we flushed the system using a pressure washer..hoses are all correct and we did bleed the system numberous times but there were always air bubbles in the system when checked again
 
Had same prob this year and end of last turned out it had a small crack in head gasket letting air into water jackets i did not find it till i took head off for the second time. I just took them apart and used two good gaskets on each cyc. More snapper
 
(back) opposite direction of the normal flow. when you are bleeding are you rising front and back of sled?
 
Is a hose kinked or crushed? I don't get this. It flows, but only under high pressure. It's strange. There has to be an obstruction or a hole in something big enough to divert flow only most of the time.

Recheck the obvious: worn parts, are the hoses connected correctly, coolant level, lift each end of the sled to remove air, have a second set of eyes look at it.

As a last resort, disconnect each exchanger and check for obstructions on each individual item including the motor to find it.
 
doesnt it have a thermostat on it ?? sounds like it doesnt work properly ..maybe try without it .. just for a test ....could be a air lock cause from a warp head too .. weird it doesnt do it at 7000 rpm maybe it flow enough to push that air that come from compression head leak ...
 
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