Coolant system service

[2004Tiger]

I have spent several days changing my coolant and learning how the system works. Thanks for the previous posts with information on refilling fluid and the overflow tank. I might still have a problem: my system would only accept 2 quarts, which is .95 quart short of the spec in my owner's handbook.



I wanted to do this because my engine temp guage was approaching the danger zone when running at low revs around town and when idling. The fan would come on but the temp would continue to rise (not moderate at mid-gauge as others have posted to be normal). Last week I was gadding about town on errands and I let it idle in front of a shop as I ducked in. (Had a starting problem, fixed with a new battery now.) When I came out there was a large puddle of coolant under my bike and the temp guage was in the red. Rode it home one mile and the temp dropped somewhat.



I drained the fluid from the plug halfway up the cylinder and also at the bottom hose connection. (Did all the fluid come out? I don't know as I didn't measure it because of the puddle already mentioned.) I disassembled the cap/filler/thermostat and tested the t-stat in boiling water. Works OK. Reassembled. Fill system slowly at cap neck until fluid rises in the bleed screw hole. Seems to be full. Remove windscreen and cowl to access overflow tank, discovered overflow hose and vent hose are reversed from the factory. This was apparently causing my overheating condition by stealing fluid from the engine and not replacing it. Also the plastic hose elbow at the side of the tank (the vent hole which was wrongly connected to the coolant system filler neck) was broken, probably from my overtemp blowout. So I emptied the overflow tank, bought a new elbow, and connected the hoses properly. (Foothill BMW/Triumph in Lakewood did not have the part, as they have not had anything I needed either BMW or Triumph. Erico in Denver had it and was much cheaper, only 90 cents. I'm finished with Foothill.) I filled the overflow tank up to the MIN mark. At this point I have used only 2 quarts of fluid.



Install gas tank, start the engine. Idle and rev until hot, and fluid dribbles out of the overflow hose. The fan starts and temp gauge max at mid-dial. Good, no overheating as before. Shut off engine to cool. Remove gas tank, remove coolant cap to check level. Full. Remove bleed screw, full of fluid on other side of t-stat. Squeeze hoses, no bubbles.  Also, no fluid has been drawn from overflow tank to engine upon cooling.



Again, install gas tank, run engine until hot, fan runs, temp guage max at mid-point. I have a house fan directed at the radiator and ambient temperature is 90F. Operation seems to be correct. Stop engine, let cool, remove gas tank, check coolant level. Full. No change in overflow tank.



I have now ridden a little around my neighborhood and the temp gauge stays just above the low mark. At idle it rises to mid-point and the fan keeps it there. No overheating. Much better. I need to go on a longer ride to verify.



It all seems good now, but has anyone ever poured more than two quarts into their system? Is the handbook wrong at 2.95 quarts?

[Jim S]

I don't think you could completely drain the fluid without stripping the engine so probably some coolant lift in the system when you drained it. If all's working as normal then I reckon your problems are over.

With the engine up to temp and the t/stat open it should bleed any air back to the expansion tank so if it's settled down now that should be it. I've drained mine but didn't notice how much I put back in, sorry.

I've not had any issues since I refilled mine, over 3000 miles since.

As long as there's no sign of bubbles or excess coolant coming from the overflow then I reckon it's sorted.

[2004Tiger]

I have now ridden an hour loop into the foothills, twisty paved and unpaved. Before my cooling system service on this ride the temp gauge would fluctuate from normal warm up to almost red. Now it stayed at normal warm the entire loop.



I also rode downtown, mostly freeway, some stop and go. Ambient temp 90F. Before, the temperature would rise at each stop. Now it stays low.



I'm gaining confidence that the overheating problem has been solved. Thanks for your reinforcement.