Sprint Overheating

My 1999 Sprint ST 955i likes to overheat. I have made sure the pump is working, the fan cuts in and the thermostat is not stuck shut and put a new radiator cap on. I have filled the coolant slowly and tried to make sure that there are no air locks by burping it. Yesterday I rode to work with the temp gauge slowly rising to the red and coolant coming out of the overflow (it is 12 miles). Today I removed the thermostat and went for a short ride once I had topped the coolant up. The gauge slowly rose up to the red and stayed there. Fan was working and still coolant being blown out. I am now at a loss to check next - I have flushed the system through with clean water and it all comes through with no issues. Am I looking at head gasket failure? Engine runs ok I think ( I have nothing to compare it to) although idle is a little up and down, stalls occasionally and can be difficult to start when hot. If it is the gasket how difficult is it to change? The bike has done 112k by the way!

 

Well I have concluded it is HGF. Milky oil and blows coolant out quickly. Do I change the gasket or sell the bike as is? Almost full MOT with no advisories.

 

I bought the bike knowing it overheated. I have replaced the water pump as the impellor blades had fallen off the previous one! That works as I checked it with the cover off to see if it rotated when the engine did. I have replaced the rad cap, replaced the oil as it was milky so the oil is fresh ( I did it twice with a new oil filter each time). I have removed the thermostat in case it was sticking - no change as well as changing the radiator. When idling the gauge slowly rises to the upper middle until the fan cuts in then it throws coolant out of the overflow. If I ride it the gauge goes into the red. I have filled it slowly massaging the pipes each time all of which get pressurised and hot. I have backflushed all as well as using a coolant flush today. Some stuff came out but since I put about the right amount of coolant in there does not seem to be any blockages. It is a little difficult to start when cold - it cranks over a good few seconds before firing and when hot it will either catch after a second or just keep going for ten to twenty seconds and try to fire. This all leads me to HGF as the symptoms are of that. If I ride it it will take the same amount of time to boil up. I have done this several times so I think it is HGF. 112k for a HG is not bad me thinks. I have a Haynes manual, a resonable tool kit, knowledge and am not afraid to take the head off. Unless I have to reseal the liners that is - that fills me with trepidation but all an experience! I thought about getting rid of it or breaking it but since I have just had it MOT'd with no advisories I feel I should change the HG as a last ditch thing!

 

Thats what I'm thinking. I've checked everything else and thats the last thing it can be I think. So new gasket and head bolts on order, just got to strip it.

 

Well took the head off and found a hole in the head gasket between two of the cylinders. So that solves part of the mystery! Got most of it back together this evening although I was so hot I looked like I had jumped into a swimmmimg pool! Tomorrow will get the rest back, work permitting, and then to start her up.

 

Well the moment of truth arrived today. I started it, it ran, it warmed up and didn't throw its coolant out. So next thing is a short ride to see if the temp needle stays at the lower end of the gauge!

 

Well after replacing the radiator, the head gasket, the water pump and the thermostat it seems I can do no more. It warms up ok but despite the temp gauge staying just above cold it throws coolant out of the overflow. I have back flushed it all to no avail. Unless anyone else has any ideas it looks like it's going up for sale!

 

Just had a suggestion from elsewhere. A warped head! Apparently not mine but on the bike! Guess its coming off again!