99 scrambler 400 coolant over-flow
After 20mins of riding the over flow cap starts to spits out coolant through the pin hole, then the light came on. Let it cool, radiator coolant level was below the top hose and sensor. Topped off coolant, lights goes out, but after warm up it's still spiting at the over flow. Fan works. Had the cap off and watched the flow inside, while revving I can see movement, strong current. At idle the flow is intermittent.
What does this tell me? Water pump?
Thanks in advance,
Rick

 

you might be leaking compression into cooling system through the head gasket.
if you can put coolant tester on the rad. or any way of measuring pressure. it will gain pressure as it runs without actually getting hot. blowing out water then it gets hot. that's what happened to me It will be more likely to get hot if it running lean as well.

 

Make sure the plastic screen in front of the radiator is clean not filled with grass seeds, etc blocking air flow and that radiator is clean front and back from any accumulated mud. Crack open the bleed bolt on the rear of the head by the temperature sensor to make sure no air is present in the cooling system then top off coolant. You can get a replacement 13 psi radiator cap for about 6 bucks at Napa or Auto Zone if you suspect the cap might be faulty, seeping past into the overflow reservoir under pressure and if you don't have a pressure tester. If head gasket is leaking you should notice more smoke than normal along with burning coolant smell. Normal for coolant flow to increase in the radiator as you get past idle and not as noticeable at idle. OPT

 

You can get a situation where the gasket is bad but not burning coolant.
just blowing all the water out. mine hit 10 psi with two blips of the throttle on a cold engine.
Does the fan come on before the coolant came out?
you may have to really flush the rad with a garden hose, or take it out wash it in the sink.

 

Thank you guys for the insite. I have changed the cap, still doing it.
I'll have to check the pressure.
The coolant will spit out before it gets hot and the fan does work when temp is hot. So sound like it might be a head gasket. How hard is it to change. It looks like I can do it with out removing the engine. What is the torque for the head nuts / bolt.

Thanks again!
Rick

 

18-20 pounds on head nut torque. Easier if you pull the tank or lift the rear of the tank up as far as getting access to rear head nuts,but not necessary,just a little tight at the rear of the head. Make sure you install the new head gasket with the word "UP" cutout toward the intake and the tab on the front of the gasket lines up with the exhaust tab on the cylinder. Don't forget to bleed all air out of the head after coolant is installed,then top off coolant in radiator and reservoir tank. OPT