BMC 1.5 trapped air after coolant change

[Tracy D'arth]

That looks like gear oil, its too clean for engine oil. Did you ever establish if there was a leaking gearbox oil cooler?

[ATO]

4 minutes ago, Tracy D'arth said:

That looks like gear oil, its too clean for engine oil. Did you ever establish if there was a leaking gearbox oil cooler?

Not yet, will look at that next time. Spent so long trying to flush the skin tank I ran out of time.

[bizzard]

Sniff it. If it smells like cats pee it's gear oil.

[ATO]

Didn't particularly smell of gear oil but then it's mixed with coolant and water. If I get the oil cooler off and blow air through one of the oil pipe unions while blocking the other, presumably a leak will be obvious.

Edited July 2, 2022 by ATO

[ATO]

It's gear oil. Oil cooler has a leak.

[Tracy D'arth]

1 minute ago, ATO said:

It's gear oil. Oil cooler has a leak.

There You Go!   😇

[ATO]

1 hour ago, Tracy D'arth said:

There You Go!   😇

 

Still got to clean out the skin tank and get back to the original problem of air in the system. Thanks for your help and suggestions so far. I'm learning.

[Slim]

On 02/07/2022 at 19:59, Tony Brooks said:

 

Should do but there is no way to be sure. Who built the hull?

 

You may have to flush it several times with a strong hot soda solution.

That's what I had to do when I got oil in my cooling system (via an engine oil cooler). Not sure if the OPs skin tank return exits the tank at the bottom. (both my flow and return are at the top of the tank) . I had to use a Pela to empty mine. 

[Tracy D'arth]

2 minutes ago, Slim said:

 both my flow and return are at the top of the tank

How does that work then?

[Tony Brooks]

4 hours ago, Tracy D'arth said:

How does that work then?

 

Vertical baffles, but not that I think it is in any way sensible.

[Slim]

10 minutes ago, Tony Brooks said:

 

Vertical baffles, but not that I think it is in any way sensible.

Not quite. The baffles are horizontal and the return (cool) has a pipe running down to the bottom of the skin tank. The builder showed it to me before it was all welded up. This return is at the stern end of the tank. Works perfectly unless you want to drain the tank.   

[ATO]

Oil cooler replaced, all good. In the process of flushing the skin tank I realised there has to be a bleed bolt somewhere as it was clearly trapping air and there was other no way to remove it. I found it hidden behind timber framing for the floor, though it was seized solid needed a lot heat to get it moving. So I've test filled with water and it's running sweetly bang on 82c. Left it for an hour and the temp didn't move, so it looks like the original problem was skin tank air rather than calorifier. However, I'm still a bit stumped by the calorifier circuit, I've now got a hot pipe going in but the pipe coming out is still cold. Tried bleeding on the calorifier, got a spit of water, then nothing. Definitely not affecting the engine running temp though. 

[Tony Brooks]

1 hour ago, ATO said:

Oil cooler replaced, all good. In the process of flushing the skin tank I realised there has to be a bleed bolt somewhere as it was clearly trapping air and there was other no way to remove it. I found it hidden behind timber framing for the floor, though it was seized solid needed a lot heat to get it moving. So I've test filled with water and it's running sweetly bang on 82c. Left it for an hour and the temp didn't move, so it looks like the original problem was skin tank air rather than calorifier. However, I'm still a bit stumped by the calorifier circuit, I've now got a hot pipe going in but the pipe coming out is still cold. Tried bleeding on the calorifier, got a spit of water, then nothing. Definitely not affecting the engine running temp though. 

 

I can't remember if I said this way back in the topic, if not try this:

 

Get a helper with a watering can full of coolant mixture.

Take filler cap off

Loosen the hose connection to the copper pipe running back to the engine water pump so you can easily pull it off

With a COLD engine (so thermostat is closed preventing coolant flow to the  kin tank) set the engine to about 1500 rpm.

You pull the hose off and put your thumb over the copper pipe connection while allowing coolant to flow out of the hose while the helper keeps the engine topped up.

Look at the flow, you will probably see slugs of air coming out of the hose. When they stop so just coolant is coming out replace the hose.

Tighten hose, top up coolant level, and run up to temperature. Remember the outlet hose to the calorifier will be close to the domestic water temperature so pretty cool until the calorifier heats up.

 

[ATO]

Thanks I'll do that when I refill with coolant. I would've thought the bleed tap would have the same effect but it's clearly not the case, strange.

[Tony Brooks]

50 minutes ago, ATO said:

Thanks I'll do that when I refill with coolant. I would've thought the bleed tap would have the same effect but it's clearly not the case, strange.

 

So would I but if it works obviously not.  I think that loop above the hot take ff from the head may be trapping air. Personally I would see if I could get an elbow of bend on there to try to avoid that high loop.

[StephenA]

4 hours ago, ATO said:

Oil cooler replaced, all good. In the process of flushing the skin tank I realised there has to be a bleed bolt somewhere as it was clearly trapping air and there was other no way to remove it. I found it hidden behind timber framing for the floor, though it was seized solid needed a lot heat to get it moving. So I've test filled with water and it's running sweetly bang on 82c. Left it for an hour and the temp didn't move, so it looks like the original problem was skin tank air rather than calorifier. However, I'm still a bit stumped by the calorifier circuit, I've now got a hot pipe going in but the pipe coming out is still cold. Tried bleeding on the calorifier, got a spit of water, then nothing. Definitely not affecting the engine running temp though. 

 

If the water in the calorifier is cold then you may find that the return from the calorifier stays cold for quite some time, especially at tickover.  On Mintball when we're brining up the calorifier from cold we can run for quite some time without the return pipe starting to warm up - and that's when we're doing a good run, not working locks where the engine isn't doing much most of the time.

 

[ATO]

3 minutes ago, StephenA said:

 

If the water in the calorifier is cold then you may find that the return from the calorifier stays cold for quite some time, especially at tickover.  On Mintball when we're brining up the calorifier from cold we can run for quite some time without the return pipe starting to warm up - and that's when we're doing a good run, not working locks where the engine isn't doing much most of the time.

 

Thanks. I did consider that but got nothing out of the bleed tap on the calorifier, so assumed the outlet pipe was empty. I'll do as Tony says and that will show if it's already bled itself through.