KV6 looks like coolant leak

[SD1too]

Thanks for your helpful description Billy.

I'd suspect that the expansion tank cap is venting coolant so it's back to the basic checks:

• Is the running temperature in the low nineties (except when stationary)?
• Does the radiator fan work?
• Is the level in the expansion tank at or below the MAX marker?
• Are the expansion tank cap 'O' ring seals flattened?
• Is there an airlock (has it been filled and bled according to the MGR method)?
• Are the serrated clips hard up against the water pump and thermostat housings and tight?
• Is there any coolant residue in the 'V'?

Simon

[BillyMG]

Hi Simon



-Coolant temp was running 90-99

-Fan is good
-I fill the expansion tank to the maximum mark inside the tank as you look in but it obviously drops when it leaks

-I've bought another cap - apparently on 48 hour delivery a week ago but there's no sign of any leak from this one and the seal looks good
-I filled her up as per the Haynes with the expansion tank raised

-The clips are hard up and tight
-I took everything out again to check for leaks in the V and it's bone dry. Also tightened up the intakes and all hoses


Now I think about it when I went out to check the level last night in the dark after she'd been switched off for 5 hours and there was a release of gas from the expansion tank - more than a slight hiss and I saw some really small bubbles in the coolant which was now nearer the minimum mark. I realised it was dripping so jacked her up and had a look and as I say the only place I can see the coolant is dripping off that clip. It's dry when I stick my fingers on top of it. I might be paranoid but yesterday I saw whisp of white smoke float past me whilst I was at a set of lights - turned round to see who it was and there was nobody behind me.

[SD1too]

Originally Posted by BillyMG

-Coolant temp was running 90-99

The temperature shouldn't reach 99˚ when the car's moving Billy. If it is, then I suspoect a poor seal somewhere. Fit the new expansion tank cap when it arrives and test again.

Simon

[BillyMG]

OK fingers crossed 🤞

[BillyMG]

Replaced the coolant cap with a new one, drove around town two days no more than 40mph - nothing. Took her out on the motorway yesterday, no obvious initial leak but overnight a huge puddle. I need to take that clip off I know but I need to take the kids the grotto and just wanted to get these two videos up whilst it's leaking in case anyone can spot the problem. Really struggling with this any help appreciated lads.

The leak:

https://youtu.be/oZ7btLMqzIw

The puddle - had to move the car forward to get in my garage so positioning not important:

https://youtu.be/JMWY3bXW8ho

[Ducati750cc]

Originally Posted by BillyMG

Replaced the coolant cap with a new one, drove around town two days no more than 40mph - nothing. Took her out on the motorway yesterday, no obvious initial leak but overnight a huge puddle. I need to take that clip off I know but I need to take the kids the grotto and just wanted to get these two videos up whilst it's leaking in case anyone can spot the problem. Really struggling with this any help appreciated lads.

The leak:

https://youtu.be/oZ7btLMqzIw

The puddle - had to move the car forward to get in my garage so positioning not important:

https://youtu.be/JMWY3bXW8ho

This may be no help, but previously you have said that when the engine was cold and had been stood that you heard pressure being released when removing the cap when none should be expected.


Also that it had reached 99 deg in this weather !


Ideally you need now to do a pressure test from cold.


Before starting the engine observe the frequency of the drips, remove the cap, make sure the coolant is at the correct level, fit the pressure tester, apply a pressure just under the cap release pressure, then again observe the drops, do they increase ?


Leave the tester connected at pressure for at least 20 mins and observe the pressure and leak.



Release pressure, check coolant, re-fit the tester, run until the fan cuts in, switch off then monitor the pressure as the engine returns to ambient temperature, there should be no residual pressure.



I'm wondering if the leak is a combination of a couple of things 1) a higher than normal increase in temperature, with a consequent increase in pressure but below the cap pressure, 2) A component, hose, joint, that when subject to both expansion and pressure weeps.



I know its difficult finding the source of a leak in the depths of an engine bay but a borescope / inspection camera sometimes helps, my son with the garage has a stand-alone one, but also has one that he can use with his phone, was surprised with the quality of the pictures and uses it quite often, the stand-alone one though has features the phone one doesn't.


Hope this helps a bit, god luck with the search.

[BillyMG]

Couple of photos from above - I can see it dripping from here onto the floor but I can't see anything dripping from above it. Left and right looks dry. I'm perplexed by this.

[BillyMG]

Great thanks Ducati. Great minds think alike mate I'm just searching amazon now for a decent camera. I've also bought some fluorescent dye and a uv light. If no joy I'll follow your advice regards the pressure.

[BillyMG]

I just took the coolant cap off, there was a short blast of a
air and some bubbling in the tank but most importantly I can smell petrol in it

I did use a tester (air lock with blue fluid) the other day to test the head gasket and it didn't change colour but it only tests for exhaust gases

[SD1too]

Originally Posted by BillyMG

I just took the coolant cap off, there was a short blast of air and some bubbling in the tank but most importantly I can smell petrol in it

First of all thanks for the videos, they are very good. The coolant almost looks as if it's seeping out of a joint and forming a droplet doesn't it.

Your discovery of a smell of petrol in the coolant is a useful clue. Could it be the LH bank inlet manifold gasket where these two fluids pass each other separated by an elastomer seal? That might be a good place to start looking for further evidence.

Simon