Radiator confusion ST1100

Zider drinker

Zider drinker

Joined
May 5, 2024
Messages
42
Age
59
Location
Somerset UK
Its another basic question but the manual says one thing and a Youtube video by a ST1100 fan says something else.
1.Do you top up the radiator by the overflow plastic bottle on the rear right or do you indeed have to take multiple plastic fairing pieces off to get to the radiator itself and the traditional screw on radiator cap?
My UK Haynes manual suggests the plastic overflow but its not very clear which to be fair is rare for that type of manual.I know in the states you have the Clymer manuals.
Also any type of coolant or should it be bike specific?
Regards Ziderdrinker UK
 
Needs to have no silicates in it as they will wreck the water pump, IIRC.
I used Honda HP for years but I have swapped over to Evans Waterless - more expensive but no water in it.
It's in two of my four ST1100s and will be in the other two when I do the water pump replacements.
You should be able to replenish from the overflow bottle - assuming the hose is good (notorious for cracking at the 'neck').
But I don't mind removing the bodywork and filling her up at the neck so I can 'see' it.
 
Top up the radiator by the thermostat housing where the main cap is (it’s not right on the radiator as would be thought). You need to remove: the hard bags, the 2 side covers (easy), then remove the false tank (air cleaner cover), then the right gray panel with the lockable compartment (and to remove this, you need to remove the right service cover (the rhombus shaped cover through which you can see the valve cover). Drain the radiator via the left lower (as if you’re riding the bike- left) petcock (little tough to access (better to take the left lower fairing off after removing the large gray fairing at the bottom). Once you drain the radiator, you use a short length of hose over the filler neck to blow (not too hard otherwise you’ll make a mess to get the residual coolant out)- (if you’re going to flush the system, you then use some distilled water and fill, run engine, drain, and blow it again). I just drained and refilled as my coolant was in very good condition (didn’t even have 20K miles on it). Use a syringe and flexible tubing to suction out the coolant of the overflow bottle as well (unless you’re removing it to clean it out).

The above seems very complex…it’s really not, just mostly getting the panels off. When I did my 2 ST’s I would say each took maybe an hour to do (OK, maybe an underestimate on the time). I didn’t use the Evans as Phil did- I used Prestone 15 year/ 350K mile coolant (and it is silicate free- it’s OAT, organic acid technology). As Phil said, no silicate formula only (a lot of folks here feel more comfortable using the Honda blue stuff, and that’s fine, just more $$$ (and I’m cheap!).
 
Last edited:
Thanks for this and now I know what the OAT stuff is.I think the non organic stuff is lethal for cats and dogs etc so ill keep an eye on where I store the old coolant.Much clearer now thanks Erdoc48 and as always Uncle Phil.
 
Putting distilled water in to flush it does very little because the thermostat prevents coolant from completely draining from the block. There are block drains but difficult to get to. Drain, add coolant it will be fine. Make sure the overflow to reservoir isn't plugged common problem. The hose should be tight. Over time the hose end becomes stretched so you can cut 1/2 inch off each end and that will insure a good seal.
 
Last edited:
This works for car or bike but a properly maintained cooling system will only require filling of the over flow bottle. I have probably 60K miles on Honda type 2 car fluid and my bike likes it. I figure if its good for an 80,000 dollar premium Acura automobile its good enough for my lowly St1100:rofl1:
 
As I understand it - If there is fluid in the reservoir bottle, you top up the bottle. If there isn't, then you need to top up at the radiator cap.

The bottle is there to ensure that excess fluid - due to heat expansion has somewhere to go. Similarly when the fluid contracts due to cooling, it can suck up fluid from the bottle.

The manual describes this as a 'siphon'. It needs fluid in the tubes and no air to work effectively.

Layman's description follows. Check it in the manual.

So a maintenance top up to replace fluid lost to small leaks or evaporation requires just the bottle to be topped up. Full fluid replacement or If the level has gone below minimum in the reservoir bottle - the fluid needs to be added at the radiator cap and at the bottle, and air needs to be bled from the system by blipping the engine with the radiator cap off.
 
jfheath said:
As I understand it - If there is fluid in the reservoir bottle, you top up the bottle. If there isn't, then you need to top up at the radiator cap.
Click to expand...
... and if the overflow line is cracked hence leaking air into the system, you'll end up with a solid looking level in the reservoir, but an already half empty cooling system, blowing your head gaskets while at it ... :cautious:

If it doubts you need to check proper levels via the rad-cap...
I'd managed to do that (and refill) by reaching up aside the RH fork tube, undoing the cab, topping up by using a small funnel with a piece of hose attached...
With bike on side-stand (ensures thermostat housing being the highest point, hence vent all tapped air), start the engine and let it idle (do not blip the throttle!) while observing the level in the filler neck, top off when required, but once the liquid movement inside gets stronger (=> thermostat opens), kill engine and place cap back on; remember to twist it over both notches to close fully.
 
ST1100Y said:
With bike on side-stand (ensures thermostat housing being the highest point, hence vent all tapped air), start the engine and let it idle (do not blip the throttle!)
Click to expand...
Ah. I assumed the ST1100 would be the same as the 1300 in this respect.
1300 manual says - (amongst other things):

Start the engine and let it idle 2-3mins.
Snap the throttle 3-4 times to bleed air from the system.
Stop engine and add coolant to filler neck.

The Honda common service manual says the same.

Is putting it on the side stand a better way of doing it ?

It's an academic question as whenever I change the coolant, the bike is up on the ramp - to save my aching bones - so the side stand option is not available.
 
I drained and blew out the old coolant then replaced with the ethylene glycol based coolant that I bought at Walmart. 8 bucks and everything seems to be working just fine. Took 3/4 gallon to refill. images (3).jpeg
 
Road Slug said:
I drained and blew out the old coolant then replaced with the ethylene glycol based coolant that I bought at Walmart. 8 bucks and everything seems to be working just fine. Took 3/4 gallon to refill. images (3).jpeg
Click to expand...
Does that stuff have silicates in it - just curious?
If it does, you will be in for a 'surprise' down the road.
 
Unfortunately you cannot fill the radiator/t-stat housing from the reservoir, since it’s located lower than the filler neck. Closely inspect the hose from the filler neck, if there are any cracks, replace it.
 
I have found 3 overflow hoses cracked/split right where it comes off the radiator on the bottom of the hose.
 
Ron said:
I have found 3 overflow hoses cracked/split right where it comes off the radiator on the bottom of the hose.
Click to expand...
Yep, frequent maintenance item to inspect, clip like 15mm off and re-attach the hose...
Installed a new line during my recent service of the '00 ST1100Y (t/belt, etc...), was looking to replace the overflow line with a fitting braided silicone one, but couldn't locate one in time (they only sell 1m long pieces) , so the OEM braided rubber it was...
 
You must log in or register to reply here.
Back
Top Bottom