Engine dumping coolant... suggestions please

[Nostrodamus]

Still got a problem. I have put less coolant in which seemed to be a bit better but this morning when the system had cooled down I took the radiator cap off to find the coolant right at the top again. When I run it for a short time I know this level will then drop to below the top of the heat exchanger. it is really weird as if there is some back pressure holding it there but if I run it again the level will drop to below the top of the heat exchanger.

 

[owen-cox]

You're not overfilling with coolant, are you?

If I overfill ours, it usually comes out through the overfill/pressure release and settles at the appropriate level as per the manual.


ps. Not having much luck this season, are we?

This could be the problem. Sun sail had a whole fleet of 30 boats and this happened every time they were topped up. Not good for clients coming to collect a boat with antifreeze in the bilge when they pick it up. Hard to convince them it's a good engine. It took a while to learn where the level is. In the end we put little catch bottles under the overflow but once we learned the level they didn't need it.

 

[john_morris_uk]

Under normal conditions the pressures in various parts of your water systems are:
Fresh water about 20 psi dependent upon the pressure switch fitted
Coolant around 12 psi dependent upon the cap
Seawater nominally atmospheric in an open ended system.

So if there are any leaks anywhere they will go from high pressure to lower, but not the opposite. However, many Volvo engines accumulate salts in the exhaust manifold that can increase backpressure in the seawater system until it exceeds coolant pressure. There have been many examples on this forum in which the seals in the heat exchanger have given way under this reverse pressure, driving seawater into the coolant which overflows into the bilge.

The first, easiest and cheapest thing to check is the manifold, just a matter of taking it off and cleaning salts out carefully. Don't attack it with a screwdriver as many have driven theirs right through the walls. With luck that will fix it but sometimes the seals are displaced in the heat exchanger and need to be put back in place.

If coolant does not leak when the engine is not running it is probably not the calorifier. If coolant is found first thing in the morning when the domestic water pump has been switched on all night it is almost certainly the calorifier coils that are perforated. I have known three of these in the past couple of years.

Although I was not aware of the details of the pressures, those are exactly my thoughts. We had lots of very similar problems until I finally bit the bullet and took the injection elbow off. It was severely blocked and a soak in various acids (brick cleaner, patin cleaner etc) sorted it out. The problem of excess coolant coming out of the overflow when the engine had heated up instantly stopped.

Its not going to cost the OP very much if anything to remove the exhaust elbow (Maybe a couple of £ for a new gasket?) Its one of the first places I would be going for to solve the problem as described.

 

[Bobc]

I've had this with the same engine, and I reckon I can take you straight to it.

Take the radiator cap off, and inside you'll find a rubber seal. I bet you that's shot. It only needs to be a bit knobbled to leak, and that does exactly what you say (dumping coolant down the overflow pipe).

Replacement seals are about £4 from your VP shop.

I went through the whole "head gasket/top end strip-down/yada yada" on the advice of a so-called professional, and it was only when it was still doing it after the re-build that I discovered what it was (which really pi**ed me off).

Here you go. Item no. 9. Part number 1543751 - £4.92

http://www.volvopentashop.com/DBMarine/en-GB/Details/PentaPartsCatalog/7746710_046?path=MarineDieselEngines%2F7746710%2F7746710_26%2F7746710_046

Best of luck.

Bob

 

[Nostrodamus]

Thanks Bobc but I don't have an expansion tank, just a normal radiator cap but it is worth replacing and trying it first.

I am having troubles finding the fluid level and where it should be topped up to. One time I run the engine and later take the cap off to find the level at the top of the radiator and the next time I do the same it is just below the top of the heat exchanger. I really has me baffled but it looks like I need to clean the elbow to start with.

 

[Bobc]

Ok, worth replacing though if you have one of those seals in there.

Also, can I suggest that you strap a pot into the bay and run the overflow pipe into that. Then at least you will be able to see how much coolant is going there and also you can keep putting it back.

Don't forget also that the radiator cap is designed to be a pressure relief valve, and if you have too much coolant in the tank, it is designed to bleed some out to relieve the pressure.

Best of luck.

 

[Nostrodamus]

Ok, worth replacing though if you have one of those seals in there.

Also, can I suggest that you strap a pot into the bay and run the overflow pipe into that. Then at least you will be able to see how much coolant is going there and also you can keep putting it back.

Don't forget also that the radiator cap is designed to be a pressure relief valve, and if you have too much coolant in the tank, it is designed to bleed some out to relieve the pressure.

Best of luck.

Thanks Bobc

 

[Bilgediver]

We have a volvo MD22 P-B engine that will motor for several hours with no problems. Then at some point the about a litre of coolant ends up in the bilge under the engine. It gets there through the overflow pipe which is on the neck of the radiator cap.
I cannot understand why it does it. The radiator cap I would suspect is about 15 years old so the pressure spring may be worn but why do it only after several hours.
It may of course be something completely different but any suggestions would help as I am at a loss.

Do you have a calorifier?

 

[Nostrodamus]

Yes, I turned the feed off yesterday to it to see if it is letting water into the system

 

[Nostrodamus]

Just an update on what I have tried so far
I turned the inlet and outlet valves to the calorififier off at the engine so no coolant was going to it. It didn,t seem to make any difference.
I took the exhaust elbow off and it was pretty clean but I did clean it up some more. I fould it is some cast steel and pretty heavy but the heat exchanger is aluminium. I did get a new exhaust elbow. Mr (I would rather rip the wings off butterflies) Volvo wanted £550 for a new one but Perkins make exactly the same one in aluminium for £120. Unfortunately when I fitted it I found that there was corrosion at the point where the new gasket fits the heat exchanger and it would not form a seal so allowing the exhaust gases to escape. I had to put the old one back on which fit better but still had to seal around the gasket as gases were still escaping.
Water flow is good and with no load on the engine it is pretty cool. I have noticed that there seems to be to me too much pressure in the great exchanger. I have a normal type radiator cap on the heat exchanger with no header tank. If I run the engine up to temperature one day there is still pressure on the cap the following day and it comes off with a pop.
There does not seem to be oil in the coolant or coolant in the oil.
I have sent for a new radiator cap and thermostat to try and exclude them.
If it is not them then I am left with the expensive options of a leak in the exchanger (which does not seem right as this should not cause pressure) or blow head gasket or warped or cracked head.
I looked in the manual and it says the coolant level should be between the cap and spur what ever that means. My level seems to want to settle so the top of the heat exchanger in coolant can just be seen. Does anyone know wat is the correct level. As I don't have an expansion tank I presume there must be some gap in there for the liquid to expand. There is about half a litres difference between the top of the neck of the tank and just below the to of the heat exchanger.
Any thoughts.....thanks

 

[parbuckle]

I would not discount the option that sea water is entering back past the elbow because it is not high enough above sea level especially when heeled in a seaway or possibly antisiphon system not effective also partial wet exhaust blockage maybe a kink or other hose problem . I think if this is suspected maybe removal of heat exchanger to see if any corrosion obvious around exhaust ports and inside dry exhaust area of H/E, further investigation would require the removal of the head or maybe a compression test.

 

[FlyingDutchman]

Did you take out the vent plug on the thermostat housing when you filled the cooling system? Air in the system can cause very funny symptoms including the ones you described!

 

[Nostrodamus]

Did you take out the vent plug on the thermostat housing when you filled the cooling system? Air in the system can cause very funny symptoms including the ones you described!

Yes I did that and watched the air bubble out but good point.

 

[Nostrodamus]

I would not discount the option that sea water is entering back past the elbow because it is not high enough above sea level especially when heeled in a seaway or possibly antisiphon system not effective also partial wet exhaust blockage maybe a kink or other hose problem . I think if this is suspected maybe removal of heat exchanger to see if any corrosion obvious around exhaust ports and inside dry exhaust area of H/E, further investigation would require the removal of the head or maybe a compression test.

I checked and cleaned the antisiphon which is well above water level and we dont heal too much. I we was healing that much I would have the engine off and be sailing. Good point though. I have checked all the hoses which seem ok. As you say the next is the removal and checking of the HE and then the head.
I think it was said when all else is eliminated the only possibility, however improbable is what is left.. the expensive one...

 

[parbuckle]

I checked and cleaned the antisiphon which is well above water level and we dont heal too much. I we was healing that much I would have the engine off and be sailing. Good point though. I have checked all the hoses which seem ok. As you say the next is the removal and checking of the HE and then the head.
I think it was said when all else is eliminated the only possibility, however improbable is what is left.. the expensive one...

Sorry did not want to play devils advocate but you had not mentioned the option that somehow sea water was getting back into dry exhaust it was the corrosion you said was found on flange made me think it was a possibility . The more recent Volvo heat exchangers are quite different to the initial model with end caps and jubilee clips they appear more complex but possibly more secure against leaking problems.

 

[gonad]

try cleaning out the heat exchanger

 

[Nostrodamus]

We are at anchor at the moment and going into a marina now is too expensive. When we can get in one I will strip it all down but thanks for the suggestion.
Strange thing is I can run the engine for an hour or two and it cools perfectly. Just seems the pressure is building up slowly.
Still trying to find out what the correct level to fill the coolant level to is but have had no replies

 

[Cardo]

Still trying to find out what the correct level to fill the coolant level to is but have had no replies

From page 33 of the instruction manual found here:
http://www.dolcetto.org.uk/download...anuals/Volvo Penta MD22P Instruction Book.pdf

Top up coolant so that the level reaches the lower edge of the filler pipe.

 

[Bilgediver]

Yes, I turned the feed off yesterday to it to see if it is letting water into the system

I am more thinking that you have an air pocket in the calorifier and this expands when hot. See if there is a way of removing air using a top connection. This is air in the heating circuit.

 

[Bobc]

I would seriously advise AGAINST taking the head off the engine. The heads on these are really soft and warp very easily. You'll probably end-up having to have it stripped, skimmed, and new valves etc. Also, the tappet shims are impossible to get now, so you might end up not able to get the valve clearance right when you put it back together.

I would also suggest that removing the heat exchanger should be a option only taken if you are getting REAL cooling problems. They are made from a horrid ali that chorodes, and if you can get it all apart, the chances are that you won't get it all back together again without some hacking/welding/bodging.

Think carefully before taking spanners to it.

Ask me how I know...