Bleeding air from the cooling system?

[Carmel2]

Hi,

We have a Volvo Penta 2040 and it seems air is getting into the cooling system, ie the filler overflow cap is doing it's job, but it keeps on happening mostly when we are in idle. I have not overfilled the system. I ran the engine without the filler cap on for about 20mins the other day and that seemed to do the job.........famous last words. Now it's happening again. Any bright ideas on where the air might be coming from and where I can bleed it from?

 

[vyv_cox]

Is the filler cap at the highest point in the system? In water cooled VW vans the top of the radiator is higher than the filler cap on the rear engine. It is necessary to add coolant with the engine running to completely fill it, usually turning over at about 1500 revs. Garages sometimes make up a long tube brazed to an old filler cap with the centre cut out to ensure the water there is higher than anywhere else.

 

[Carmel2]

Yes the filler cap is the highest point on the engine. When I ran it the other day coolant was basically spitting out of the top so I didn't feel any more could be added.

 

[orizaba]

do you have a calorifier,(hot water heater) they can sometimes trap air in the system ,
though to be fair usually once the air is bled out it should not return, gues the other question is , is the engine getting hot/over temprature

 

[Carmel2]

do you have a calorifier,(hot water heater) they can sometimes trap air in the system ,
though to be fair usually once the air is bled out it should not return, gues the other question is , is the engine getting hot/over temprature

Yes we do have a calorifier which I did bleed when all this started. As for overheating, I don't think so. We motored for 4 hours today and everything seemed ok until the last mo when we were in idle for a while before reversing on the anchor, and then there was a nice puddle in the engine bay from the overflow.

 

[vyv_cox]

I'm not a Volvo expert but I have come across a similar problem on PBO. For water to be driven out of the fresh water side something is displacing it. If the pressure cap is working as it should, whatever is displacing the coolant has to be at a pressure higher than the cap setting. This can normally only be achieved by a leaking head gasket but it sounds unlikely that this is the cause in your engine.

In the cases that I recall it transpired that seawater was being driven into the coolant through the seals in the heat exchanger. I understand that these are tricky to set up correctly. Under normal circumstances the pressure on the seawater side should be lower than in the coolant but in the cases i mention the manifold was partially blocked with salt, increasing the pressure of seawater in the exchanger. I would suggest that your next move might be to check your manifold.

 

[Carmel2]

Thanks Vyv. As part of our recent engine service we had the whole manifold removed, cleaned and ground flat as the fittings were quite pitted. A new thermostat was added at the same time.

 

[chrisgee]

Hi,

We have a Volvo Penta 2040 and it seems air is getting into the cooling system, ie the filler overflow cap is doing it's job, but it keeps on happening mostly when we are in idle. I have not overfilled the system. I ran the engine without the filler cap on for about 20mins the other day and that seemed to do the job.........famous last words. Now it's happening again. Any bright ideas on where the air might be coming from and where I can bleed it from?

had the same problem and (seemed) to have solved it by fitting a small overflow tank which I have always had on previous Yanmar engines. The excess water which I guess is just from expansion goes into the tank and stays there to the medium level i filled to.
Hopes this may help you.

 

[Carmel2]

I just took the filler cap off after about 5 hours of the engine being off and quite a lot of air pressure came out, including a good splash of coolant all over the place. This seems like a lot of pressure.

 

[TRUNDLETRUC]

Pressure in engine.

We had a Volvo MD2030 with water problems. It kept losing the freshwater. The answer was the stupid rubber seals on the ends of the heat exchanger. Volvo does not provide sufficient metal on the inner element to give the jubilee clips enough purchase. They therefore gradually slip off and you get engine water and sea water mixing.
In your case it would do not harm to check these rubber seals. Is the sea water system blocked a bit? Check filter, syphonic valve closing? Then I would get the pressure of the filler cap checked at a garage or borrow another one? Then check the tube where the sea water enters the exhaust system after the heat exchanger. If this is blocked it will create pressure which will squeeze past the stupid rubber seals.
Now for the serious stuff - Check the thermostat, Is it blocked or not opening? You may need to take off the water pump to get at this? and while you have the water out of the engine flush the calorifier system and the engine.
If all this fails I'm sorry I think you are looking at a new cylinder head gasket! Engines can be very annoying. Best of luck.

 

[Carmel2]

We are in a fairly remote anchorage so internet is on the iffy side. The heat exchanger was taken off and cleaned out, milled and new gaskets were put on less than 25 engine hours ago.
Last night when the filler cap was taken off I could just about feel the coolant with my finger, this morning with the cap being off all night the level had risen to the overflow???????
I have just run the engine and did what Vyv said ie putting coolant in while it's running.....well I say in, most of it went all over the show, so I shall wait and see.

 

[vyv_cox]

In view of your later postings about work completed very recently it seems very likely that the problem, or at least part of it, is in the heat exchanger seals. Several people have discussed similar problems in the past. Another contributor may be the pressure cap. If this was not working it is conceivable that the pressure on the seawater side would be higher than on the coolant side.

From what you have told us so far I cannot believe that air is getting in. It has to be water.

 

[grafozz]

check

check the anti siphon valve , it could be gummed up and allowing water out ?

 

[charles_reed]

Having just gone through similar travails, I would suggest the problem to be on your calorifier feeds. Check all the joins and the actual pipes, I found a small cut on the inlet feed, caused by the UJ rubbing against the pipe, caused by a retaining clip failure.
Coolant loss starts as minimal, but air replaced coolant when the engine was running and the expansion tank contents refilled the system as it cooled. As the calorifier has 5l of coolant, the engine 3l and expansion tank 3.5l any leak is slow to show by drops in level.

 

[vyv_cox]

Sorry Charles, I don't follow that. I can see that a leak inside the calorifier coils could allow domestic water to enter the coolant side, but how can a cut hose do so? Assuming the coolant to be pressurised by the cap, a leak should be easy to find. How does air enter a pressurised hose?

 

[charles_reed]

Sorry Charles, I don't follow that. I can see that a leak inside the calorifier coils could allow domestic water to enter the coolant side, but how can a cut hose do so? Assuming the coolant to be pressurised by the cap, a leak should be easy to find. How does air enter a pressurised hose?

merely relating exactly what happened. sorry you can;t follow - perhaps on wrong tack

Theorising, coolant, under pressure, forced out through cut when engine running, level in engine heat-exchanger drops, to be replaced by coolant from the expansion tank as the engine cools.
Though the OP is unaware, before removing the cap there is probably a partial vacuum in the engine cooling system, on removing the cap air gets in.

The leak when finally found was still inly about 1ml/5' and stopped when the engine wasn't running.
I'd purged the calorifier circuit (virtually no air) and run the engine several times before I found the problem.

 

[vyv_cox]

OK thanks, I can follow that one. I don't think the OP has an expansion tank. I find leaks of antifreeze solution fairly easy to spot but maybe in his case the engine overflow and possible hose puncture leak are mixing?

 

[Carmel2]

I don't think it's the calorifier as this did leak and was welded successfully, I was present at the pressure test, plus the hoses were inspected. It was my first thought though. I will get the boat to Lakki tomorrow and get the Volvo rep out as this is all a bit beyond me.

 

[kroot]

Hi,

We have a Volvo Penta 2040 and it seems air is getting into the cooling system, ie the filler overflow cap is doing it's job, but it keeps on happening mostly when we are in idle. I have not overfilled the system. I ran the engine without the filler cap on for about 20mins the other day and that seemed to do the job.........famous last words. Now it's happening again. Any bright ideas on where the air might be coming from and where I can bleed it from?

when you say(now it's happening again) what exactly is happening ? I am experimenting with a fwc myself, my first start-up it went up to 180 and I turned it off. I just read about a bleeding system that I put together,now my thermostat housing has a 1/8" npt fitting that is a bleeder to begin with,so I went to the auto store and purchased a brake bleeder that has a 1/8" npt bushing and a bleeder that threads into it and I attached a clear hose w/clamp to bleeder so while the engine is running I'll have the bleeder open with the end of the hose leading into a can, I am waiting for a inline thermostat housing to come before I try it

 

[nortada]

Welcome to the forum.

Got to ask how did you find it why did you resurrect this 8 year old thread here?

Rather than an old thread in Liveaboard Link, you are far more likely to get answers with a new thread in Reader to Reader?