# mk3 overheating issue?



## ccmd8v (Mar 22, 2007)

I have an issue with my mk3 overheating, it's a 2.0, I went over everything I could think of: thermostat, the water pump works, plugged hoses, radiator, fans dont come on, but when I run them with the ac it still overheats, leaks, yadda, yadda. Anyone have any other solutions?:banghead:


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## jorge r (Apr 27, 2006)

do the top and bottom radiator hoses heat up? as an indication that coolant is flowing into the radiator.


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## ccmd8v (Mar 22, 2007)

they do, but apparently the bottom hose doesnt get hot enough.


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## jorge r (Apr 27, 2006)

When the coolant level is low, coolant will not flow well into the radiator. With the coolant not making contact with the radiator coolant temperature sensor, the radiator fan will not turn on. The coolant level needs to be checked after each time the engine cools down until the coolant stays topped.
The thermostat long part should be inside the water pump housing, in case there's a coolant flow problem.


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## ccmd8v (Mar 22, 2007)

something somewhere isnt working right, i checked the impeller on the pump and its fine, im starting to think the overheating was from the leak, but when i ran stop leak in it (one of the stupidest things ive prob. done) it partly clogged the radiator.


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## jorge r (Apr 27, 2006)

I used stop leak on my car, and made it home across the Mojave dessert. It was a leaking water pump to engine block o ring. I used half the bottle of stop leak or so, fixed the severe leak almost instantly. 
I replaced the water pump and flushed it a couple of months later, AND, the steam hole on the head was clogged, I poked it with a wire, a guitar string actualy. The steam hole is where the small hose to the coolant jug top connects, make sure that one is cleared out.


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## ccmd8v (Mar 22, 2007)

Ahhh, i'll get on that. but how would that contrubute to it overheating? (sorry dont know much about the cooling system)


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## ccmd8v (Mar 22, 2007)

no more overheating! think the radiator had a plug.


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## jorge r (Apr 27, 2006)

After using a sealer, I think the steam hole will clog. Not related to the overheating issue but the head needs to circulate coolant properly, including steam buildup relief.
Any steam or gas in the engine coolant jacket will go to the top, to the head, need to get rid of that gas thru the small hose or the head may get some hot spots.


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## ccmd8v (Mar 22, 2007)

Thanks for all the help! I went and flushed the system, so its all good now.


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## dkfackler (Feb 8, 2010)

jorge r said:


> The steam hole is where the small hose to the coolant jug top connects, make sure that one is cleared out.


Yeah, if that is clogged you get an air bubble at the top of the system and the pump can't push coolant past that because the air just compresses. That WILL cause an overheat. Look in to the coolant reservoir with engine running to see if the small hose from the cylinder head is streaming a bit of coolant. It's small at idle and increases with engine RPM. If you get nothing, or just a tiny bit well above idle, raid your Les Paul or Strat for a string and clean that port.


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