Time For Another Uncle Phil ST1100 Mystery Thread

Uncle Phil

Uncle Phil

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In The Holler West Of Nashville, Tennessee
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4 ST1100(s)
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Frost, my 97 ABSII has now decided to start running hotter than normal.
Not in the danger range but mid gauge when there is plenty of air flow.
Fan is kicking at the right spot, plenty of coolant, overflow bottle hose good on both ends, new water pump, no signs of coolant leakage, overflow bottle at correct level, all hoses new. With Evans Coolant you can run it with the radiator cap off so I made some interesting observations -
1. There appears to be little flow until it gets hot enough for the fan to kick on.
2. The flow is good until the fan kicks off then again there is little flow.
I know I what I think it is but say ye?
 
Seems your thermostat is about to buy the farm...

When I fill an ST coolant system, I let it idle/warm up with the rad/cap off and observe; and that thermostat opens long before the temps get even near where the fan comes on...
 
New thermostat in (BTW you don't have to remove the upper fairing as the Service Manual states, the fairing pocket is enough).
I reckon I'll see if that was the issue when I have time to take her out for a road test.
It never overheated it just ran hotter than a ST1100 should normally be running.
Now the fan kicks in about halfway on the gauge so maybe that was it.
 
FWIW, mine has been doing that same thing with the gauge for many years. Its erratic, sometimes it does it, sometimes not. Seems like when the weather heats up its more likely to do it, but its still pretty random. I suspect its the gauge itself because sometimes it will creep up quickly, and then go back down quickly sometime later. That also, is random, only does it occasionally.

I never opened up the rad cap to observe coolant flow for obvious reasons, but I've replaced the T-stat, the temp sender, the water pump, and the rad cap. Nothing changed.

It hasn't been discussed here in recent years, but others mentioned similar symptoms quite a while back IIRC. When I replaced the WP and saw the condition of my old one, I was sure that was going to fix the symptom, but it didn't.

Since it doesn't affect the running of the bike, I just ignore it. When my gauge creeps up at speed it usually only goes to just left of vertical, so not into the fan-on zone. When I'm stopped or moving very slowly, the fan will kick in at just past vertical as it should, every time.

So I'm curious about yours and if the new T-stat has any effect.
 
All the grounds are fine AFAIK at this point.
It just started on the last trip so once I road test it I'll see if the TStat fixes it.
I chased a similar problem a while back and it appeared to have been lack of flow in the radiator.
When I replaced it, the problem 'solved' itself.
If the new TStat doesn't fix it, I'll probably swap out the radiator next.
But after I replaced the TStat on this one, I saw a much more normal flow with the cap off.
That's one of the things I really like about Evans Waterless coolant - you can run it while hot without the cap and see what is going on.
The only 'disadvantage' with Evans is if you spring leak and fix it, you can't use water to top it up.
But chances are if you spring a big leak, you ain't gonna fix it on the road anyway. ;)
And you could always drain it out and put in 'normal' antifreeze to get you home I guess.
 
When I was trying to diagnose the gauge issue on my 97, I used an ohm meter connected to the temp sender on the right side of the engine. The workshop manual will give you the resistance value of when the Tstat opens and when the fan should kick in. In my case the system functioned normally but my gauge did not, and eventually I found the ground issue. I did a temporary fix by putting a ground jumper to the gauge. It was months later I found that the main ground was loose on a bolt to the folding grab handle.
 
When the temp is up check the radiator for cold spots, The cooler sections are probably internal blockage. When the fan comes on check for air flow, Or pull it and hold it up to the light to see if the fins are plugged.
If the entire radiator is warm, the entire internal portion is getting coolant flow. Now it becomes a external check. My ST1300 radiator has become plugged with road grit enough that it has become inefficient and I couldn't soak the stuff out,
Did locate one with lower milage and installed fender extension and back to better cooling again.
 
Tell me if I’m wrong…with Evans coolant, you don’t need a high pressure cap (my brother uses Evans in his 300ZX and said he went with a low pressure cap- keeps the hoses soft/non pressurized, even when the engine is hot, so even if you have a leak, it drips, doesn’t shoot from any hole in the system)- for water/coolant cooled systems the pressure cap (1.1 Bar/ ~ 16 PSI) is needed to avoid the coolant boiling off due to lack of sufficient pressure in the system. I just experienced this with my 2000 as it wasn’t overheating but for certain was running hotter on the gauge than what I’m used to seeing. On a hunch, I changed the cap (was the original) and this corrected the problem (also smelled a very slight odor of the coolant but didn’t see it all over when I took the plastics off)- changed the cap pre-emptively on the 94 as well. There was a very modest loss of coolant in the overflow (just a few fl. oz.) and I had previously filled this to the upper line when I recently changed the coolant (at the cap neck it was completely full). I took the bike out yesterday and it runs as it did in the past (warms only to just above the second line on the left (~ 10:30 position). Also, no coolant smell yesterday when riding. From what I understand about Evans (and I’m no expert), since is is 100% glycol, it’s not quite as heat absorbing as water or a water solution, but there’s also no points of ‘steam formation’ in the cooling system that can occur with a water/ coolant mix, so therefore is technically a better product (and officially boils at 365 degrees F if memory serves). As Phil said, it can’t be mixed with water (or should not be), and typically is permanent coolant.
 
Erdoc48 said:
Tell me if I’m wrong…with Evans coolant, you don’t need a high pressure cap (my brother uses Evans in his 300ZX and said he went with a low pressure cap- keeps the hoses soft/non pressurized, even when the engine is hot, so even if you have a leak, it drips, doesn’t shoot from any hole in the system)- for water/coolant cooled systems the pressure cap (1.1 Bar/ ~ 16 PSI) is needed to avoid the coolant boiling off due to lack of sufficient pressure in the system. I just experienced this with my 2000 as it wasn’t overheating but for certain was running hotter on the gauge than what I’m used to seeing. On a hunch, I changed the cap (was the original) and this corrected the problem (also smelled a very slight odor of the coolant but didn’t see it all over when I took the plastics off)- changed the cap pre-emptively on the 94 as well. There was a very modest loss of coolant in the overflow (just a few fl. oz.) and I had previously filled this to the upper line when I recently changed the coolant (at the cap neck it was completely full). I took the bike out yesterday and it runs as it did in the past (warms only to just above the second line on the left (~ 10:30 position). Also, no coolant smell yesterday when riding. From what I understand about Evans (and I’m no expert), since is is 100% glycol, it’s not quite as heat absorbing as water or a water solution, but there’s also no points of ‘steam formation’ in the cooling system that can occur with a water/ coolant mix, so therefore is technically a better product (and officially boils at 365 degrees F if memory serves). As Phil said, it can’t be mixed with water (or should not be), and typically is permanent coolant.
Click to expand...
Interesting - I never thought about a low pressure radiator cap as I just use the one I already had. But since there is no pressure that should be fine. I've got Evans in one of my other ST1100s have had no issue using the OEM cap. And this one had no problem until this last trip, which I do think was a thermostat going south. When I do the water pump/timing belt change on the other two ST1100s, they will get Evans also.
 
Is it the guage or the felt heat that is higher? I run across this occasionally on my 1100. Its more noticeable right after I change coolant then it gets ok a couple of weeks later its ok. I will look and see if my exhaust header bolts are loose or the gasket has gone bad since my exhaust seems louder than it did.
 
The cap change is only based on less pressure in the system as the boiling point of the Evans is so high (my brother indicated you can run the car hard- his is a twin turbo version- take the radiator cap off and the coolant just sits there- doesn’t boil over). If you use a lower pressure cap (and I wouldn’t blame you at all for NOT changing it as it’s a PIA to get to it on the 1100) I guess it exerts less pressure on the hoses, etc. so less chance of a ruptured hose. As for red one’s post, it didn’t seem any hotter just the indication per my gauge. Now all is well with mine specifically with the new cap- maybe mine wasn’t holding pressure (as much) as for what it was rated. I had a similar experience on my 300ZX years ago (mine with Prestone coolant) and a new cap fixed everything then (mine is the non turbo version). My brother’s 300 is running Evans for the past several years.
 
I am not understanding this low pressure cap with Evans waterless coolant. If it doesn’t boil under regular or hard running, then where is the pressure coming from, besides the water pump and differentials of smaller diameter hoses, and radiator channels?
 
Sunday Rider said:
I am not understanding this low pressure cap with Evans waterless coolant.
Click to expand...
An OEM cap is set to ~1.5 Bar (~21psi) to lift the boiling point of the (regular) water based coolant well over 120°C/250°F...
As Evans has a higher boiling point to begin with (AFAIK 190°C/375°F) no increased pressure required; a "softer" cap will ease venting any trapped air into the expansion tank...
 
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