Volvo penta D1-30 Air pockets in the coolant system - how to bleed?

[GavDog]

I have just flushed and changed the coolant in my twin volvo penta d1-30s and I can't seem to get rid of the air and so the total amount of coolant put in so far is only 2.5 on port and 3 litres on starboard. Anyone know how best to bleed the air? Thank you!

[GavDog]

Ps, the thermostats were replaced too with brand new ones but I don't believe they are working correctly as engines are definitely heating up too much

[DougR]

The freshwater system should be self bleeding, but there are a couple of things to look at.

First, are you sure you drained all the coolant? Drained from the block and the heat exchanger drains? This might explain why it only took what it did....

Make sure that the metal nipple connecting the air bleed hose (small hose) from the heat exchanger to the expansion tank is open. This nipple has a rather small opening and it can get restricted by a bit of debris. This makes it difficult to bleed and fill completely. Remove the hose at the HE end and clean the nipple with a piece of wire or similar. Then blow thru the hose into the expansion tank with the tank cap removed. Should be free flowing.

Remove the tank from its bracket and lift it as high as possible with the cap off. This can help bleed air out. Wouldn’t hurt to run the engine with the tank held up like this with the cap off of the tank.

Is there a hot water heater circuit connected to the engine? If so, no part of the circuit should be above the engine or it may air lock. Might require a vent fitting to allow bleeding.

[tkeithlu]

DougR speaks with wisdom. I will only add that you might try running each engine without a thermostat installed. While it will run cold longer, the eventual stable temperature should be the same as with opened thermostats. If it still overheats, the thermostats are not your problem.

You can also test the thermostats with a saucepan of water, stove, and thermometer that reaches boiling. The temperature at which they open is quite obvious.

[GavDog]

Many thanks for the quick and helpful reply. Yes definitely completely emptied as I cleaned out the heat exchanger and removed the 2 nipples on each engine + replaced the thermostats on both. Also cleaned out the coolant expansion tanks.

There is no hot water system on the starboard engine but there is on the port. Looks like everything goes below the engine as you said.

I did clear the small hose going into the tank and the HE + blew into it + raised the expansion tank to maximum height and squeezed the hoses, all which helped originally but new thermostats still don't seem to be opening.

I will next try running the engine with the expansion tank off. Didn't realise I could do that as thought it would go everywhere?

I can't get back to my boat until later in the week so if you have any other ideas in the meantime then I'll make myself a list to try and work through them all when I get back.

Thanks so much!

Originally Posted by DougR

The freshwater system should be self bleeding, but there are a couple of things to look at.

First, are you sure you drained all the coolant? Drained from the block and the heat exchanger drains? This might explain why it only took what it did....

Make sure that the metal nipple connecting the air bleed hose (small hose) from the heat exchanger to the expansion tank is open. This nipple has a rather small opening and it can get restricted by a bit of debris. This makes it difficult to bleed and fill completely. Remove the hose at the HE end and clean the nipple with a piece of wire or similar. Then blow thru the hose into the expansion tank with the tank cap removed. Should be free flowing.

Remove the tank from its bracket and lift it as high as possible with the cap off. This can help bleed air out. Wouldn’t hurt to run the engine with the tank held up like this with the cap off of the tank.

Is there a hot water heater circuit connected to the engine? If so, no part of the circuit should be above the engine or it may air lock. Might require a vent fitting to allow bleeding.

[GavDog]

Many thanks for your help! If I take the thermostats back out, will coolant flow out everywhere? Do I have to drain it all again? Thanks again!

Originally Posted by tkeithlu

DougR speaks with wisdom. I will only add that you might try running each engine without a thermostat installed. While it will run cold longer, the eventual stable temperature should be the same as with opened thermostats. If it still overheats, the thermostats are not your problem.

You can also test the thermostats with a saucepan of water, stove, and thermometer that reaches boiling. The temperature at which they open is quite obvious.

[skipperpete]

Originally Posted by GavDog

Many thanks for your help! If I take the thermostats back out, will coolant flow out everywhere? Do I have to drain it all again? Thanks again!

I think your overheating issue relates to your previous threads redolent with blocked stainless steel elbows, thick black exhaust emission and the mysterious “ pinhole in the injector pump”. The likelihood of 2 new thermostats failing out of the box is Zero.
You need professional help.

[GavDog]

I don't think the thermostats are failing, I think there is an air pocket issue causing them not to recognise the heat. The elbows are now all clear and the pinhole on the starboard side was fixed.

I'd I take the thermostats out to test that, will all he coolant gush out? I.e do I need to drain again first?

Thanks

Originally Posted by skipperpete

I think your overheating issue relates to your previous threads redolent with blocked stainless steel elbows, thick black exhaust emission and the mysterious “ pinhole in the injector pump”. The likelihood of 2 new thermostats failing out of the box is Zero.
You need professional help.

[Newf1]

When you say you appear to be overheating, do you have individual temperature gauges and if so what are they reading? The reason I ask is on my 2014 D1-30 the thermostat doesn't start to open until the temperature reaches 194F and not fully open until 221F.

If you are sitting and idling after you attempt to refill the coolant you may not have reached that opening temperature.

I have replaced my coolant a couple of times over the years and have never had an issue with air in the system. Filled it up through the coolant tank, ran it up to temp and topped it off as required.

[GavDog]

No temperature guage but the block is getting very very hot as soon as I've run at 2000rpm or more for 5 mins. I'm definitely short on amount of coolant too! At least 1litre still should be able to go in so it's air blocking somewhere. Many thanks

Originally Posted by Newf1

When you say you appear to be overheating, do you have individual temperature gauges and if so what are they reading? The reason I ask is on my 2014 D1-30 the thermostat doesn't start to open until the temperature reaches 194F and not fully open until 221F.

If you are sitting and idling after you attempt to refill the coolant you may not have reached that opening temperature.

I have replaced my coolant a couple of times over the years and have never had an issue with air in the system. Filled it up through the coolant tank, ran it up to temp and topped it off as required.

[GavDog]

Just about to head back to the boat on Saturday NZ time, does anybody know if I remove the thermostat will coolant gush out? Ie do I have to drain coolant again first? Or can I just remove it and put the cover back on? Thanks!

[DougR]

If you remove the thermostat you will loose the amount of coolant that is in the heat exchanger itself, but not all the coolant in the block. Just open the petcock on the heat exchanger and drain that amount of coolant. Don’t mess with the drain on the block.

[GavDog]

Originally Posted by DougR

If you remove the thermostat you will loose the amount of coolant that is in the heat exchanger itself, but not all the coolant in the block. Just open the petcock on the heat exchanger and drain that amount of coolant. Don’t mess with the drain on the block.

Thank you so much, that's helpful to know