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Intermittent coolant blasting out from overflow tank that has no low or high markings.

This topic has been covered by a few threads but I still have a question.

I purchased a 2008 Corsaro Avio second-hand, downloaded a manual and have sorted, fixed everything except this one sporadic issue.

It has an intermittent habit of blasting coolant from the overflow container after I’ve come to a stop, sometimes with the motor still running or after I’ve just switched it off. This does not necessarily occur when the bike is hot, eg it can occur prior to the fans kicking in at 95 degrees or afterwards. The bike is definitely not overheating.

At first I thought the previous owner might have overfilled it but it happened a few times without me topping up the coolant. When I checked the radiator (engine cold) the fluid level seemed low (about half full). In summary I don’t think it was overfilled.

All the radiator pipes are still fixed with the original Morini clamps and I haven’t seen any evidence of other sources of fluid leaks including from the well documented problematic one on the right hand side.

There is no water in the oil, the coolant does not seem to be contaminated (visual inspection only) and I am hoping ‘fingers crossed’ there is no head gasket issue leading to an over pressurisation of the cooling system.

I am hoping for the quickest/easiest fix being a faulty radiator cap not holding pressure/spring not allowing the coolant to escape or drain back into the radiator at the right pressure.

As they don’t cost much I have just ordered the equivalent KTM 1.0 bar radiator cap part (p/n 45135009000) as they have these in stock in Australia so I should have it within a few days.

I am hopeful (really, really hopeful) the replacement radiator cap will fix the problem.

Before I get too excited I want to make sure everything is OK by ensuring that I have the correct amount of water/coolant in the system noting that I have not topped/replaced the coolant that was previously spat out.

The painful thing is that the coolant overflow tank has absolutely no low or high marks on it anywhere. I even pulled it out to check and there are no marks at all!

Can someone with a Corsaro that is lucky enough to have these markings on their overflow tank please post a good quality photo so I have something to use as a guide.

Other questions……………

1. With the bike level should I top up the radiator up to just below the filler neck and leave the overflow tank empty? or
2. With the bike level should I top up the radiator up to just below the filler neck and fill the overflow tank to the imaginary/estiamted low mark? or
3. With the bike level fill the overflow tank to the imaginary low mark when cold without topping up the radiator (currently the tank looks like it’s about ½ full) and slowly toping it up this way until the levels align with the Low (cold) and High (warm) marks?

Cheers

hello X1er
on the first image you can see Ive marked 2 lines (to show you) where I keep my coolant level, on the second picture it shows the expansion pipe from the rad it is important that the coolant level is always above this pipe as it relies on a vacuum within the circuit created by the coolant expanding as the engine gets hot and then contracting as it cools this ensures the rad is always full and airlock free
when you top the rad up it needs to be completely full including the pipe running to the top up bottle (expansion tank pictured) there is a small bleed screw to help achieve this shown on the works manual pg142 11/06
also there is a small hole in the centre of the cap on the expansion bottle make sure it is not blocked as it needs to let air in as the engine cools
give the top hose a good squeeze after you have topped up as I have known it to push trapped air up into the expansion bottle
the only other thing is the thermostat but I don't think you have a thermostat problem as you either see it taking forever to get up to temperature (meaning its stuck open) or over heating (stuck closed)
Hope this helps you find a solution
vtxbrit

Hi X1er;

I had a similar problem on my GP (which is not quite the same as the reservoir filler cap has a pipe that runs back to the radiator), except this resulted in loosing coolant through the pipe from the pump blowing off - twice. This was cured - I hope - after the second time by the then importer under warranty back in 2012, using a more prosaic jubilee clip fixing as opposed to the original elegant clip (this is became a standard Factory solution until they changed the casing design). The GP runs hotter - the fans come on at 98 Celcius instead of 90 - and the warning light comes on if it exceeds 103...

Since then I've kept a close eye on engine temperature and coolant level. I noticed on one run shortly after the second fix that the coolant level was up to the filler cap, and so I reduced the level by taking a small amount out. When cool, I noted where the level was and did similar to vtxbrit by marking the reservoir with a felt tip line (long since gone).

My rule of thumb is that the tank should hold coolant over the bottom third with the bike held level - I'd suggest that on your next run where the fans come on, you check the height of coolant in the tank and if it's within a limit you feel acceptable mark the level when home (and the engine has cooled) as your 'max'. Minimum level needs to be at least some coolant showing in the reservoir to cover the radiator intake, again as noted by vtxbrit.

It's worth noting that in the Corsaro user guide (page 58 if you have it in English) suggests leaving the engine running for a few minutes if it's been used "at high environment temperature"; I've always taken this to mean if the fans are running when you stop, let them run until the thermostat switches them off!

Let us know how you get on, and Good Riding,

CC

When I return from the IoM I'll be servicing the Corsaro - including changing the coolant. Mine has never had much in the expansion tank. I will refill and see what happens. Bleeding the system of air is important, I had a VW Golf with air in the system - did not end well for the engine!

Always a good idea to leave running if fans on, the engine will get hotter for a short while when switched off so advisable to let it cool to fans off before switching off.

Sorted.

When draining the coolant I noticed that it did not drain out constantly. At one point nothing came out followed by more coolant. I'm guessing it had some air in there.

Replaced coolant and followed the air bleeding procedure as per the manual.

New KTM radiator cap installed, these are available locally here in Aust for $13 (7GBP?) and the KTM part is EXACTLY THE SAME as the original Morini one. I probably didn't need to replace it but did so anyway.

Overflow container topped up to the level as per the pictures.

A few test rides later and everything is as it should be.

Thanks

The KTM looks - but isn't - the same, as it has a different valve that opens at higher pressure. The morini original opens at 1.0 bar.

The KTM equivalent radiator cap is identical to the Corsaro’s.

It is 1.0 bar and has the same valve set up.

The KTM part number is for KTM LC 50 as per the table of interchangeable parts listed on this website. This table lists the correct part number.

Both are the same internally and externally and have all the same identical markings on the cap. Both are made in Italy. It’s safe to assume that they’re produced by the same manufacturer and used by various motorcycle makers

I have seen on this forum a thread / picture of 1.4 bar(?) KTM radiator cap. This is not that cap and I ‘m not sure why you would even consider fitting a cap that operates at the wrong pressure.

Hope this clears things up.

Certainly did! Thanks a lot for the part number