Faulty rad cap? - Hoping not a head gasket

5.5 days into our 7 day road trip through the Snowy Mountains region in Australia I noticed my bike had started pushing coolant out the overflow. No abnormal temps on the dash or anything like that. Kept an eye on the engine temp and rode 40 odd km to the next small town to strip the fairings off and see what I could find (still drips out the overflow). No oil / water mixing evident at all so I went on the hunt for another rad cap which was always going to be a long shot for a higher pressure cap in a tiny country town. The best I could do was a 1.1 bar cap when I needed a 1.6 bar item. Knew it wouldn't do the job but filled and bled the cooling system and threw it on with the hope it would get me to the next biggest town about 60km away.

Bike was still spitting coolant as expected when I arrived with temps the whole way only in the normal range of 2-3 bars on the dash. Still couldn't track down a high pressure cap anywhere within the town or a 300km radius. Called it, put the missus into a motel and jumped on her RSV4 to freeway it 400km home. Grabbed the trailer, got back there at 1:00am and towed the bike home next morning.

My Dealer is relocating and appears won't be open for another few weeks. I don't trust the other new dealer around me mechanically. Proven pretty hopeless to me in past and I won't go back for service work. I'll try the 1.8 bar cap off my track bike and vacuum bleed the cooling system to check for myself meantime but the questions are how many people had had issues with radiator caps and what's the likelihood of a head gasket issue? Bike is a 22 build pani V4S with 15,000 kms on it now. Never overheated only road use. Obviously if the cap doesn't fix the bike pushing coolant it'll go to the dealer and is what it is.

Forgive my naivety if this is a foolish question - since it wasn’t actually overheating, could you just add water to the overflow occasionally and continue riding?

If you have a blown head gasket you can usually see a stream of bubbles coming to the top of the radiator when the cap is off and the thermostat is open. On the Pani's/SF's it seems the thermostat opens a little before the 3rd bar lights.

craig bush said:

Forgive my naivety if this is a foolish question - since it wasn’t actually overheating, could you just add water to the overflow occasionally and continue riding?

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To me wasn't worth the risk of dumping too much coolant and overheating when I was 250+ miles from home and pretty much in the middle of nowhere. When I saw both reservoirs had no fluid in them it wasn't a small volume lost at all.

baggerman said:

If you have a blown head gasket you can usually see a stream of bubbles coming to the top of the radiator when the cap is off and the thermostat is open. On the Pani's/SF's it seems the thermostat opens a little before the 3rd bar lights.

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Yeah I know what you mean but hard to tell in this situation on the side of the road if that's air bleeding out of combustion that keeps coming through. I'll do a proper vacuum fill of the system and check. Maybe easier to just buy a tee kay tester.

Ok so still learning all the Ducati V4 things and it appears to be a water pump. Was unaware that the water pump weep hole in the V has a hose connected to it and tees into the second coolant reservoir drain. Booked in at dealer for warranty. Fingers crossed for good parts supply.

Mcv4 said:

Was unaware that the water pump weep hole in the V has a hose connected to it and tees into the second coolant reservoir drain.

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What year bike?

ETA: The parts diagram for the 2023 reflects this change. I've read about guys drilling and tapping the weep hole for a hose barb and running a line but didn't know this was a factory change. Sucks that they haven't found a way to make a water pump that doesn't grenade itself though.

Before I decided to travel on mine long distance I cogitated on this a bit. Every failure, except one, I found was to the outside. The exception was on a bike with the original pump part #. I think for revision 1 the face load on the seal that is to the outside is made lower by intent. This helps insure that when the bike gets overheated, which is easy to do on these, that it always fails allowing coolant to leak to the outside instead of into the oil. My bike has the first revision pump (2nd part #).

Given what they'd already done for the first revision adding a hose to the weep hole to recover coolant is a reasonable solution. The real solution would be to increase the diameter of the pump shaft. Cheaper to do what they've done. This way the original pump housing is retained etc.

bp_SFV4 said:

What year bike?

ETA: The parts diagram for the 2023 reflects this change. I've read about guys drilling and tapping the weep hole for a hose barb and running a line but didn't know this was a factory change. Sucks that they haven't found a way to make a water pump that doesn't grenade itself though.

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It's an MY23 so makes sense. 15,000kms so I'm not that unhappy but seems like it's been common for a while now and you'd think they could do something about it to rectify. Interestingly enough the dealer said they'd done a few in earlier years but not as common of late. Maybe because nobody puts miles on these bikes.

baggerman said:

Before I decided to travel on mine long distance I cogitated on this a bit. Every failure, except one, I found was to the outside. The exception was on a bike with the original pump part #. I think for revision 1 the face load on the seal that is to the outside is made lower by intent. This helps insure that when the bike gets overheated, which is easy to do on these, that it always fails allowing coolant to leak to the outside instead of into the oil. My bike has the first revision pump (2nd part #).

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Definitely no overheating for me (which makes sense now) and you'd think that the overflow reservoir system should take of this with the water pump not being part of the equation.

baggerman said:

Given what they'd already done for the first revision adding a hose to the weep hole to recover coolant is a reasonable solution. The real solution would be to increase the diameter of the pump shaft. Cheaper to do what they've done. This way the original pump housing is retained etc.

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The only thing they've done with the additional WP weep hose is drain the leaking coolant to the ground instead of into the V of the block. Sounds like they need to do something to the pump though!

So no recovery geez ducati. The shaft diameter needs to be increased. But this won't allow for direct replacement on earlier models, plus they had inventory so instead of really fixing it they reworked the inventory so they could insure it leaks to the outside cause it's cheaper to replace the pump under warranty instead of the motor if it's been pumped full of coolant. They'll correct this when they rev the whole motor. These motors run really hot. Someplace I converted the bars to temperature (at least at the transitions between bars). When mine hits 4 bars if it doesn't recover immediately I'll shut it off. This discussion was useful because I think I'll drop the cap a couple of PSI.

Mcv4 said:

It's an MY23 so makes sense. 15,000kms so I'm not that unhappy but seems like it's been common for a while now and you'd think they could do something about it to rectify. Interestingly enough the dealer said they'd done a few in earlier years but not as common of late. Maybe because nobody puts miles on these bikes.

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I think prior to 2021 water pump failures were more common and there was a revision to the water pump for the 2021 model year. The new tube routing just allows the rider to know there’s a problem before there’s a really big problem.

bp_SFV4 said:

I think prior to 2021 water pump failures were more common and there was a revision to the water pump for the 2021 model year. The new tube routing just allows the rider to know there’s a problem before there’s a really big problem.

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Agreed. Easier to spot.

baggerman said:

So no recovery geez ducati. The shaft diameter needs to be increased. But this won't allow for direct replacement on earlier models, plus they had inventory so instead of really fixing it they reworked the inventory so they could insure it leaks to the outside cause it's cheaper to replace the pump under warranty instead of the motor if it's been pumped full of coolant. They'll correct this when they rev the whole motor. These motors run really hot. Someplace I converted the bars to temperature (at least at the transitions between bars). When mine hits 4 bars if it doesn't recover immediately I'll shut it off. This discussion was useful because I think I'll drop the cap a couple of PSI.

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If you lower the cap pressure from 1.6 bar it will also lower the boiling point of the coolant which has the potential to make things worse no?

With the factory coolant mixture the boiling point is way up there. The seals leak because the pressure forces fluid past the seal lip. Lower the pressure less leak. That being said mine doesn't leak and has about 10K miles. Yours had a bad pump because it shouldn't be leaking at 2 or 3 bars. With the std cap I think the boiling point of the mixture I use (25% coolant, distilled water, redline) is about 280 degrees F. If I lower it to 250 I'm good. The heads are heat treated to harden. If you keep cycling the heat way up the heat treatment starts checking out which causes all kinds of other issues.

I think there’s a higher pressure cap on there for a reason tbh. The engine runs hot so it makes sense to raise the boiling point of the cooling system. All my s1000’s had a 1.2 bar cap. I had to swap my track s1000 to a 1.8 bar from a K series bmw which is exactly what bmw does on the HP4 Race. Rest of the cooling system is the same as a normal K46 road bike s1000rr. Helped a lot with temp and associated spitting coolant out the overflow.
The heads are cast aluminum right? Normally a lot of high heat cycles in a cast alloy head will soften the head. At least in all the sport compact circuit and drag vehicles I’m involved with for work.

Mcv4 said:

I think there’s a higher pressure cap on there for a reason tbh. The engine runs hot so it makes sense to raise the boiling point of the cooling system. All my s1000’s had a 1.2 bar cap. I had to swap my track s1000 to a 1.8 bar from a K series bmw which is exactly what bmw does on the HP4 Race. Rest of the cooling system is the same as a normal K46 road bike s1000rr. Helped a lot with temp and associated spitting coolant out the overflow.
The heads are cast aluminum right? Normally a lot of high heat cycles in a cast alloy head will soften the head. At least in all the sport compact circuit and drag vehicles I’m involved with for work.

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You’re in the sport compact community? In what capacity? I have a big turbo Supra and have been active in the community here in the US since ‘07. My car is originally sport roof now converted to hardtop with a roof skin purchased from one of your suppliers there in Australia.

craig bush said:

You’re in the sport compact community? In what capacity? I have a big turbo Supra and have been active in the community here in the US since ‘07. My car is originally sport roof now converted to hardtop with a roof skin purchased from one of your suppliers there in Australia.

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Cool! Shoot me a pic though.
I’ve been the sales manager for Nitto Performance Engineering since the start of the business about 16-17 years ago. Same at Turbosmart for many years prior to that. We do a lot of Nissan RB parts but also work closely with Gas Racing over here with their 2J packages. Do all their custom piston and alloy rod drag stuff. New crankshafts coming for them too. Not as big / fast as 2J’s in the states but still running high 5 second passes with our gear. Many of the well known RB / SR / 4G / Barra cars internationally running our parts.