Coolant hoses replacement

DikkieDikkie

Joined
Jul 22, 2026
Messages
8
Age
26
Location
Den Haag
Bike
ST1100 '96
Good morning! What do people buy when they replace the cooling hoses? Already over 100€ for 4 hoses, which feels a bit ridiculous to me since they dont have many crazy bends... Should I just buy some length and 90° pieces and make it fit that way?

Also, does someone know what diameter gas line the ST1100 uses?

Thanks very much!
 
My first set of these fitted perfectly, serving well in my '00 ST

www.ebay.at

Fits for 1991-2002 Honda ST1100 Silicone Radiator Coolant Hoses Kit Replacement | eBay

Fits for 1991-2002 Honda ST1100 Silicone Radiator Coolant Hoses Kit Replacement | Vehicle Parts & Accessories, Motorcycle & Scooter Parts & Accessories, Engine Cooling | eBay!
www.ebay.at

the next set I ordered for my '94 ST came with one hose missing >5mm in length, impossible to install...
eBay is like a box of chocolate... you'll never know what you get... ;)
I will however order there again the next time the '94 is in for overhaul...

for the overflow and bypass line I ordered some in proper dimensions here (also in black of course! ;)) :


also flawless in both bikes, might require new/different constant pressure clamps due the increased wall-thickness/outer diameter...


For safety reasons I'd go with OEM fuel lines...
 
ST1100Y said:
My first set of these fitted perfectly, serving well in my '00 ST

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the next set I ordered for my '94 ST came with one hose missing >5mm in length, impossible to install...
eBay is like a box of chocolate... you'll never know what you get... ;)
I will however order there again the next time the '94 is in for overhaul...

for the overflow and bypass line I ordered some in proper dimensions here (also in black of course! ;)) :

[/URL]

also flawless in both bikes, might require new/different constant pressure clamps due the increased wall-thickness/outer diameter...


For safety reasons I'd go with OEM fuel lines...
Click to expand...
Thank you again very much for the help! Good to hear these hoses are working well on the bike, I've read the silicone hoses are not as good with organic coolants used in for example the ST1100, as for example EPDM hoses. I will soon order a set (like end of next month) and who knows, I might be able to go for a ride before fall hits :o. Other parts are on their way (alternator o-ring, coolant elbow o-rings etc), so still plenty to do ;)
 
Dunno... :shrug2:

so I googled the issue:

Coolant Type
Silicone Hose Compatibility


Ethylene Glycol (EG)
Excellent


Propylene Glycol (PG)
Excellent


Organic Acid Tech (OAT)
Excellent


Hybrid OAT (HOAT)
Excellent


as for the mechanical shaft seal on the ST1100 w/pump its important to use silicate free, permanent coolant (OAT [organic acid technology]) and replace every 4 years to avoid acid buildup...
 
I have silicone hoses in my 300ZX that have been there 14 years with OAT coolant and zero issues- they are basically forever hoses. The OEM rubber hoses are a bit more expensive but I did buy them years ago for my hose changes on both bikes because I didn’t want to struggle with the bends in the hoses.
 
ST1100Y said:
Dunno... :shrug2:

so I googled the issue:

Coolant Type
Silicone Hose Compatibility


Ethylene Glycol (EG)
Excellent


Propylene Glycol (PG)
Excellent


Organic Acid Tech (OAT)
Excellent


Hybrid OAT (HOAT)
Excellent


as for the mechanical shaft seal on the ST1100 w/pump its important to use silicate free, permanent coolant (OAT [organic acid technology]) and replace every 4 years to avoid acid buildup...
Click to expand...
Well that definitely didnt happen here (as fas as I can tell), with every hose I pull off more (acid?) crystals fall out :LOL:! Ohwell, I reckon for the first start ill fill the system with demineralized water and flush all the crap out, then fill it with the appropriate coolant after.

Thanks @Erdoc48 and @ST1100Y, thats given me some confidence :)
 
DikkieDikkie said:
Good morning! What do people buy when they replace the cooling hoses? Already over 100€ for 4 hoses, which feels a bit ridiculous to me since they dont have many crazy bends... Should I just buy some length and 90° pieces and make it fit that way?

Also, does someone know what diameter gas line the ST1100 uses?

Thanks very much!
Click to expand...
I refurbished my 1991 about six years back and replaced ALL the tubes/hoses. I took the old hoses to a local auto part store and they let me match them up...inside diameter and bend. A lot of the new hoses had to be well trimmed to match the lengths of the old ones. vacuum, water, fuel straight tube ID's were easy....just make sure you don't confuse fuel with air hoses. Even found near-matches for the little 90 degree elbows under the fuel tank.
 
DikkieDikkie said:
... fill the system with demineralized water and flush all the crap out, then fill it with the appropriate coolant after...
Click to expand...
DI-water and dedicated coolant circuit cleaner (Liqui Moly 1804) is always a good plan on an older engine...

But as said, I'd go all the way, including the O-ring set on the chromed "water pipe" down between the cylinders...
 
ST1100Y said:
DI-water and dedicated coolant circuit cleaner (Liqui Moly 1804) is always a good plan on an older engine...

But as said, I'd go all the way, including the O-ring set on the chromed "water pipe" down between the cylinders...
Click to expand...
Almost forgot to mention this
As you remove hoses, note the condition of the fitting where the hose was attached. I simply can't leave a quick job uncomplicated so I bead blasted the radiator fitting....the one with the overflow hose and fill cap attached. What looked like good mating surfaces were exposed as having deep corrosion pits which had been filled with a pinkish-silver tinted aluminum corrosion. So I ended up replacing that one and the little fittings under the air cleaner in the area between the cylinders.
My bike looked nearly new when I bought it. The PO had apparently cared for it over the years it spent in his garage.
But.....'rust never sleeps'.
 
When you replace the radiator hoses, do NOT overtighten the clamps. Those spigots are thin metal and are easily collapsed by the clamp pressure.
 
When I was a kid, I remember watching our family friend mechanic replace radiator hoses on cars. He smeared a black gook on the metal spigot and slipped the hose on then tightened the clamp. Anyone know what that sealant was? Why do we not use it today?
 
Oldbikefixr said:
Almost forgot to mention this
As you remove hoses, note the condition of the fitting where the hose was attached. I simply can't leave a quick job uncomplicated so I bead blasted the radiator fitting....the one with the overflow hose and fill cap attached. What looked like good mating surfaces were exposed as having deep corrosion pits which had been filled with a pinkish-silver tinted aluminum corrosion. So I ended up replacing that one and the little fittings under the air cleaner in the area between the cylinders.
My bike looked nearly new when I bought it. The PO had apparently cared for it over the years it spent in his garage.
But.....'rust never sleeps'.
Click to expand...
Agree with that, if you pull the hoses, check all the fitting for corrosion, and change out the o-rings. If they have never been touched, they will be mush... recent example...


https://ohioriver.smugmug.com/May29-2025/i-6xhNXpx/A][/url]
 
I'd be changing the aluminum elbows as well as long as you're in there. Cheap insurance.

This is one of those very infrequently done jobs. I always take a slew of photos as I disassemble things to ensure I put it all back together properly.
 
ReSTored said:
I'd be changing the aluminum elbows as well as long as you're in there. Cheap insurance.
Click to expand...
not cheap insurance, its a necessity.

Reports here of people re-using them only to have them fracture later on (they're cheap pot metal).

And, after taking them off, the O-rings are usually a gooey mess that isn't worth cleaning out. The picture mello dude posted of his surprised me that they can even be pried out in a single piece. Just toss them and start over with new ones.
 
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