S4R Coolant Leaking when Bike Reaches 245 Degrees

[TitanMonsterS4R]

Please shed some wisdom on a fellow rider.

Installed the new exhaust from StradaFab and rode to and from work. 35 minutes there and 45 minutes back. The morning ride was uneventful but since it was cooler around 45/50 bike didnt get too hot. On way home it was warmer closer to 65 and was in stop and go traffic. 3 times the engine temps rose to 245 degrees at which point I saw a steady stream of coolant coming from a hose on the left side of the bike. Once I got her below 245 it stopped.

Can anyone tell me why this is happening? Is the new exhaust not allowing the engine creating too much back pressure causing the engine to stay to hot? How can I remedy this issue? Both fans are working as well.

Thanks for the help.

[Speeddog]

That's quite hot.
The stream of coolant is overflow from the overflow tank, which is being fed coolant from the motor boiling the coolant inside the engine.

Have you replaced the coolant recently?

Are you using a 50/50 coolant mix?

Did you do anything else when you put the exhaust on?

Please shed some wisdom on a fellow rider.

Installed the new exhaust from StradaFab and rode to and from work. 35 minutes there and 45 minutes back. The morning ride was uneventful but since it was cooler around 45/50 bike didnt get too hot. On way home it was warmer closer to 65 and was in stop and go traffic. 3 times the engine temps rose to 245 degrees at which point I saw a steady stream of coolant coming from a hose on the left side of the bike. Once I got her below 245 it stopped.

Can anyone tell me why this is happening? Is the new exhaust not allowing the engine creating too much back pressure causing the engine to stay to hot? How can I remedy this issue? Both fans are working as well.

Thanks for the help.

[TitanMonsterS4R]

Hey Speeddog, the coolant was changed not to long ago, within the last 3 months and it was a 50/50 mix. Other than installing the exhaust I moved the oil cooler a bit to accommodate the exhaust. i will have new lines tomorrow to reroute the oil return line.

Other than that nothing was done.

Do I just need to change the coolant? Do I need to top off coolant since I've lost some?

[Speeddog]

Definitely top off the coolant in the radiator, or at least check it.

If there was coolant in the overflow tank before this episode, there may have been enough to refill the radiator as it cooled.

If there is coolant in the overflow tank now, *and* the radiator is low, there's a problem with the radiator cap, or the overflow hose from the radiator to the tank is punctured, preventing it from sucking coolant back into the radiator.

The radiator cap may be faulty, which could prevent the system from pressurizing, and thus not working properly.
Thermostat may have failed.
Not common events.

Just start it and let it run at idle and warm up, when it's up to 200 degF or so, give the hoses a squeeze, see if there's some pressure in the system.

Don't ride it very far (preferably not at all) until you get this sorted.
If it pukes coolant on your tire, it can end badly.

[TitanMonsterS4R]

Checked radiator, pretty full with coolant and the overflow is empty. Checked the top and it fastens properly.

Is the next step to run it until at 200 degrees and test hoses for pressure?

[Speeddog]

That's what I'd do next.

[TitanMonsterS4R]

Ran the bike for about 10 minutes in 40 degree weather and got her to >200 degree right around 215 for majority of ride. @ 220 the fans come on as expected and at 200+ degrees when I touch the hoses, they are not super firm and I can hear the fluid being pushed back into the radiator when I tested the hoses with the bike off but still more than 200 degrees. The overflow is empty.


Thoughts....

[Speeddog]

I suspect something's wrong with the radiator cap, but I'm not completely convinced.

The major issue is in 40 degree ambient, it shouldn't be getting over 175-180 when you're riding with any speed at all.
Something is definitely haywire.

[Speeddog]

Just got curious and looked at your newly-fitted exhaust.
Much different from what I expected.

My best advice at this point is to swap back to the previous exhaust to remove/confirm it as a suspect.

You *may* have suffered some kind of coincident failure, but likely not.
That pipe may need a good bit of fuel re-mapping.

Does it seem to run OK with it?
Idle speed?
Backfiring on overrun?
Surging?

[TitanMonsterS4R]

Just got curious and looked at your newly-fitted exhaust.
Much different from what I expected.

My best advice at this point is to swap back to the previous exhaust to remove/confirm it as a suspect.

You *may* have suffered some kind of coincident failure, but likely not.
That pipe may need a good bit of fuel re-mapping.

Does it seem to run OK with it?
Idle speed?
Backfiring on overrun?
Surging?

SD, with the other exhaust, the bike didnt do this. It rarely got to 245 degrees and ran fine.

With the new exhaust, the bike does idle fine, in fact, better than with the other exhaust. It feels like there's more back pressure, she runs like she's really tight. The bike doesn't surge much but it does have some backfiring issues. Randy and I suspected that the bike would likely have backfiring issues. I might have it tuned by Redline which has a Rexxer.

So you suspect it's either the cap or the exhaust?

[Speeddog]

I'd say it's the exhaust.

I've not seen a rad cap on a Ducati fail.
Doesn't mean it can't happen, but unlikely to coincide with exhaust fitment.
I am concerned that the hoses aren't quite firm at 200 deg.

All water-cooled Ducs in my shop ATM are non-running, so I can't check the hoses at temp.

[Moronic]

As someone who has just suffered from a coincident failure after a dyno tune, I'm sympathetic to that possibility.


Either the problem is with the cooling system, or the cooling system is fine and the problem is elsewhere.


Thing is, if the cooling system is fine, then what could be wrong that would overload it so much in such cool weather?

Especially as your primary concern seems to be the temp reading, rather than poor running.


My suspicion - it is no more than that - is a faulty thermostat. Partly because I had a similar issue intermittently on my bike a while ago.

Just sometimes, and usually after the bike had been sitting for several days, the temp reading would very quickly rise to 100C (212F) and more in cool weather when waiting at an intersection during my morning commute.

I also notice that your new exhaust runs very close to a coolant hose and the water pump area. Could that be relevant?



Very nice looking bike BTW.

Another possibility is some other obstruction to coolant flow through the system.

[TitanMonsterS4R]

Moronic, thanks. I'm hoping its a small thing as well.

I did end up wrapping the part of the exhaust that runs by the hoses to lower the heat emitted. I'm also thinking about going with Samco hoses and engine ice to lower the bike temps. I know it will only mask the true issue which is what I need to get solved before spring gets here. Riding in the temps I did a couple of days ago will be nothing compared to May, June, July and August temps.

If I can't solve I'll likely have her sent to Fast By Ferracci or Redline to have her solved and tuned. Redline might in out since they have  Rexxer.

[TitanMonsterS4R]

My suspicion - it is no more than that - is a faulty thermostat. Partly because I had a similar issue intermittently on my bike a while ago.

Where is the thermostat?

[Moronic]

Appears to be part No. 19:





Please bear in mind I have no expertise, just wanted to contribute from my experience. Had to check myself using google. In my case, mentioned the problem to my shop when they did the major service, and they checked the thermostat was operating properly and found it fine. No problems since though.

Googling S4R thermostat brought up several helpful posts on the old board from Speeddog, including this explanation of its function.