ST1100 Overheating issue

[PmodelinUS]

HI all, back agian in my spring of never ending maintenance. (AKA bike keeps needing new parts) The bike was running good and running temps were normal until Saturday night when I went out on a ride with my youngest. On the ride the temps started to running a bit high and didn't seem to want to cool down. All the radiator hoses are new within the last year and no signs of leaks, just replaced the filler neck hose yesterday, made sure I got the air out of the system, checked all my clamps and it seemed good. Then today on an errand it seemed to be running nice and cool them back to running hot and not cooling down. At this point all I can think of is teh radiator is toast (Doublt that) or the thermostat took a dump. So looking for other peoples thoughts and experiences.

Thanks
Brian

 

[red one]

Its been my experiences that the fan is not coming on when it should. Or your overflow hose is cracked or the thermostat is going bad. Might want to check those things first. When I change coolant in mine it will do like yours the first couple of cycles then stablize.

 

[Uncle Phil]

Since you changed the overflow hose (plenty of antifreeze in the overflow bottle?), my money is on the thermostat.
Unless the fan is not kicking on - which you will hear it when you stop the bike when hot (if you don't turn the key off - kill-switch it).

 

[dwalby]

can you be a bit more descriptive please, your OP is a bit vague on details.

Its normal for the ST1100 to run over a wide range of gauge temperatures during a ride, so saying "running a bit high" may be perfectly normal.

In general, it runs like this:

1. at continuous freeway speeds the gauge should stay towards the left of vertical
2. at slower speeds, say under 40-50mph, the gauge will climb, and often go past vertical and trigger the fan to come on.

Now, there are reports (and I am one of them) where the gauge shoots up to around vertical even at freeway speeds, but it eventually comes back down to the left side. Over time I've replaced the temp sensor, the T-stat, the water pump, all the hoses, and it still happens. The only other variable could be the wire to the gauge or the gauge itself, but I've learned to just live with it.

 

[ST1100Y]

The only time I had the needle raise to the right was with low coolant level, probe exposed to vapor on the highest point of the system... and the fan did not kick in as the fan-stat, still submerged in coolant on the bottom of the rad cooled by the airflow did not see high temperatures...
Fixed the leak (elbows, loss still minor at the time but enough to create the bubble mentioned), refilled, all fine...
When filling I however let the engine warm up with the rad cap off, observe the level and top off when required; once the coolant starts to wallow cause the thermostat is opening, I put the cap on...

 

[kiltman]

Around the 1 O’Clock position of the temp gauge the fan should kick in, does it do that?
There’s a possibility that it’s electrical as alluded in post #4 above. I have experienced the electrical and it was a bad ground. The behaviour of the temp gauge would be that for the first while the gauge operated as it should, on the highway it would be at the 10- 11 O’Clock position and in town between 12 -1 the fan would kick in then it would hang out near the red zone. I would turn the bike off and around 5 minutes later it was back to normal.
The culprit in my case was the ground on the loom was not fastened properly to the frame. You can check this at one of two locations. The bolt fastening the folding grab handle or the bolt holding the left pannier rail.
( I had put a ground wire to the temp gauge when I was troubleshooting and that resolved my issue)

 

[Capital]

Take out tstat, boil it in water. I bet it won’t open.
Had same symptoms, that’s how I know it (then blee head gasket with my ignorance…).
Iirc, with some patiemce you can take out tstat by removing right pocket fairing.

 

[PmodelinUS]

can you be a bit more descriptive please, your OP is a bit vague on details.

Its normal for the ST1100 to run over a wide range of gauge temperatures during a ride, so saying "running a bit high" may be perfectly normal.

In general, it runs like this:

1. at continuous freeway speeds the gauge should stay towards the left of vertical
2. at slower speeds, say under 40-50mph, the gauge will climb, and often go past vertical and trigger the fan to come on.

Now, there are reports (and I am one of them) where the gauge shoots up to around vertical even at freeway speeds, but it eventually comes back down to the left side. Over time I've replaced the temp sensor, the T-stat, the water pump, all the hoses, and it still happens. The only other variable could be the wire to the gauge or the gauge itself, but I've learned to just live with it.

When I say running hot, on the freeway or around town my temp gauge is to the right of middle and hangs around the high temp. This is not normal for my bike. Usually the gauge is to the left of center to about center is normal operating temp. The fan does come usually when I feel it should right at the right line before the your too friggin hot now red mark. Then as I pull away from the light the temp spikes into the red zone and very slowly works it way down. It's doesn't act like an air bubble that the temp goes up then drops once it passes. Acts like a car that has a bad thermostat, can't say bike as even thought I have had liquid cooled bikes never had a overheating issue.

 

[red one]

Look for the piston rubbing the themostat housing and sticking. You will find the wear marks on the shaft of the piston. At least that's what i found on mine.

 

[dwalby]

yeah, sounds like a probable T-stat issue.

If you want alternatives to the OEM part, Stant 13868 is supposed to work. The O-ring is 54x2mm.

 

[PmodelinUS]

Replaced the 50 dollar thermostat (you gotta be kidding)! At least it worked. Bikes back together and seems to be good. Old spring was awfully week feeling but not seized.

Thanks for the help as always.