Volvo Penta 2002 Overheating and No Domestic Hot Water

[saltyrob]

Hi Folks,

We have a Volvo Penta 2002 raw water cooled and today the overheating alarm went off and we also had no domestic hot water. The impellor is fine , water flowing out exhaust , changed thermostat and cold water flowing out hot tap. The raw
heating water appears to flow from a pipe in the thermostat housing to the calorifier tank tank and return to a pipe connected into the exhaust elbow. I am thinking that the flow or return pipes or tubes in the calorifier may be blocked .
Would this also cause the engine to overheat .

Your advice will be most appreciated as Mrs Salty likes her hot water .

Many thanks,

Rob

 

[RIBW]

As none of the usual experts have responded, I'll kick things off
Cheers
Bob

We have a Volvo Penta 2002 raw water cooled and today the overheating alarm went off and we also had no domestic hot water. The impellor is fine , water flowing out exhaust ...........

Water reaches the exhaust via two routes; One uses the bypass route to ensure water reaches the exhaust whatever the state of the thermostat. Once the operating temperature of the thermostat is reached (60degC for a raw water cooled engine) a second path opens up through the opening thermostat. This path routes through the calorifier ( if fitted) and then the exhaust elbow where it is mixed with the exhaust gases (and water from the bypass route.) It is normal that you should have "water flowing out exhaust" when the thermoastat has not opened.

I am thinking that the flow or return pipes or tubes in the calorifier may be blocked .
Would this also cause the engine to overheat . Rob

I would think Yes! The problem now is to identify where the blockage is occuring. Possibles include collapsed pipes to/from the calorifier, a blocked exhaust elbow or blocked galleries between the bypass tube and the thermostat.
I am assuming the thermostat is opening as you have replaced it. I am also assuming that lack of domestic water heating indicates that the water temp sensor is not faulty and providing a false alarm.

We have a Volvo Penta 2002 raw water cooled and today the overheating alarm went off ......

Identifying the specific cause means examining each possible cause. The easiest to check is the calorifier pipes which can be bypassed. But, knowledge of the engine's history may guide your suspicions.
When was the block last drained and/or flushed?
Are you sure the exhaust elbow is not blocked ? (See many recent threads about checking/cleaning/renewing)

Good luck
Bob

 

[RichardS]

I don't have a raw water cooled engine but I would have thought that the cooling water flow would not be directed 100% through the calorifier but would also have a parallel feed through the block and out through the elbow.

It sounds as if water is coming out of the exhaust so that must be going through the block now, even if it wasn't at the time of the overheat. Hold the pipes going to and from the calorifier when the engine is up to temp. If these are cool then there is a blockage or an air lock in that pipework somewhere so the hoses need to come off or you need to squeeze the large coolant pipes a few time and see if you can dislodge an air lock.

As Bob says, you could easily bypass the calorifier with a short length of pipe and his suggestion of a complete system drain and flush seems a good one as perhaps you have a moving blockage which is affecting different parts of the system as it moves around. :ambivalence:

Richard

 

[VicS]

I don't have a raw water cooled engine but I would have thought that the cooling water flow would not be directed 100% through the calorifier but would also have a parallel feed through the block and out through the elbow.

It sounds as if water is coming out of the exhaust so that must be going through the block now, even if it wasn't at the time of the overheat. Hold the pipes going to and from the calorifier when the engine is up to temp. If these are cool then there is a blockage or an air lock in that pipework somewhere so the hoses need to come off or you need to squeeze the large coolant pipes a few time and see if you can dislodge an air lock.

As Bob says, you could easily bypass the calorifier with a short length of pipe and his suggestion of a complete system drain and flush seems a good one as perhaps you have a moving blockage which is affecting different parts of the system as it moves around. :ambivalence:

Richard

The cooling system of the raw water cooled 2000 series is a bit strange. Initially all the water flows from the pump through the perforated pipe in the cylinder head and out to the exhaust elbow . When the thermostat opens it allows water to also flow out of this pipe via the perforations into the engine cooling circuit, leaving via the thermostat and the external pipe that runs across the top of the engine to the exhaust elbow.

It is the heated water flowing in this external pipe which is diverted to the heat exchanger.

Clearly in the OP's case the pump is pumping water through the perforated pipe to the exhaust elbow This is in effect the bypass. It is not flowing through the block just through the perforated pipe.

What is not happening is the flow out of the perforated pipe , though the engine , out via the thermostat , and through the heat exchanger .
First thing to check is the thermostat. It should start to a open at 60C and be fully open at 75C If thats Ok then check the rest of this circuit for obstructions.

More detail in the owner and workshop manuals on Bluemoment.com

 

[Pete7]

Is the new thermostat for a raw water cooled engine or fresh water cooled engine. Should be a 60'c for a raw water cooled engine as Vic suggested. You probably need to be sitting down when you see the price.

http://www.volvopentashop.com/Volsp...s/7726000/7726000_26/7726000_169B/7726000_178

 

[RichardS]

First thing to check is the thermostat. It should start to a open at 60C and be fully open at 75C If thats Ok then check the rest of this circuit for obstructions.

But the OP said he had put in a new thermostat so I ignored that possibility. However, as Pete7 says, maybe he used the indirect cooled thermostat if they are physically interchangeable ..... which seems rather unlikely but not impossible. However, checking the opening temperature would be a good test either way.

In correct operation, is the water flow 100% through the calorifer once the engine is up to temp and the thermostat opens? I said this seemed an unlikely design but perhaps I'm wrong.

Richard

 

[vyv_cox]

In correct operation, is the water flow 100% through the calorifer once the engine is up to temp and the thermostat opens? I said this seemed an unlikely design but perhaps I'm wrong.

Richard

As VicS has said, the Volvo 2000 series is an unusual design. The thermostat has a single disc valve, unlike Yanmar and Bukh where opening of the thermostat simultaneously opens the hot supply from the engine and closes the bypass. On the Volvo some water always passes through the perforated tube in the cylinder head but most of the hot water goes through the external pipe. This is the one that can be interrupted to add a calorifier. Photos of this arrangement on the website. https://coxengineering.sharepoint.com/Pages/Calorifier.aspx

Like this

 

[RichardS]

As VicS has said, the Volvo 2000 series is an unusual design. The thermostat has a single disc valve, unlike Yanmar and Bukh where opening of the thermostat simultaneously opens the hot supply from the engine and closes the bypass. On the Volvo some water always passes through the perforated tube in the cylinder head but most of the hot water goes through the external pipe. This is the one that can be interrupted to add a calorifier. Photos of this arrangement on the website.

I can't see what is in the photos clearly I'm afraid.

There are really only two points which can be answered easily:

1) When you say that the hot water flow is "interrupted", it is not clear whether you mean interrupted with a T-junction such that a parallel balanced flow occurs through the calorifier or interrupted as in re-routed such that the total flow is directed through the calorifier.

2) From an engineering point of view I would favour a balanced flow but, assuming that you are suggesting a totally redirected flow, if that flow is blocked at the calorifier does the thermostat have a sufficient inbuilt bypass function to allow (a presumably now increased) flow of cooling water to continue to pass through the perforated tube and thereby cool the engine?

Richard

 

[vyv_cox]

I can't see what is in the photos clearly I'm afraid.

There are really only two points which can be answered easily:

1) When you say that the hot water flow is "interrupted", it is not clear whether you mean interrupted with a T-junction such that a parallel balanced flow occurs through the calorifier or interrupted as in re-routed such that the total flow is directed through the calorifier.

2) From an engineering point of view I would favour a balanced flow but, assuming that you are suggesting a totally redirected flow, if that flow is blocked at the calorifier does the thermostat have a sufficient inbuilt bypass function to allow (a presumably now increased) flow of cooling water to continue to pass through the perforated tube and thereby cool the engine?

Richard

The 'interruption' is shown in the photo above. In the Volvo original the copper pipe on top of the engine is straight, from the thermostat to the manifold. In the photo this straight has been replaced by the one with the double elbows, with bracing between. The calorifier is connected between the two elbows. Volvo sell (or sold) a kit that added a pump and calorifier circuit to this engine, so I am not certain that the modification is theirs or not. The one in the photo appears to be DIY but I have seen others that were all green painted.

In your 2), assuming the calorifier hoses were blocked or airlocked, I believe that water would continue to flow along the perforated tube as there is no mechanism that would prevent this. In fact, if there was the engine would always overheat. Flow through the thermostat seems to be dependent upon the back-pressure developed by the three right-angled bends at the manifold, shown in my drawing at the end of the blue line.

Don't blame me for the engineering, I have been trying to puzzle it out for a long time and have reached these conclusions after lots of PMs from helpful Volvo users

 

[VicS]

I can't see what is in the photos clearly I'm afraid.

There are really only two points which can be answered easily:

1) When you say that the hot water flow is "interrupted", it is not clear whether you mean interrupted with a T-junction such that a parallel balanced flow occurs through the calorifier or interrupted as in re-routed such that the total flow is directed through the calorifier.

2) From an engineering point of view I would favour a balanced flow but, assuming that you are suggesting a totally redirected flow, if that flow is blocked at the calorifier does the thermostat have a sufficient inbuilt bypass function to allow (a presumably now increased) flow of cooling water to continue to pass through the perforated tube and thereby cool the engine?

Richard

The photo shows that the external pipe between the thermostat housing and the exhaust elbow ( red in the diagram) has been broken to divert the hot water from the thermostat to the calorifier and back again to the exhaust elbow.

All the hot water from the egine follows this path so if the calorifier is blocked there will be no effective engine cooling water flow ( just as if the thermosat failed shut) and the engine will overheat.
This is one of the possibilities to be investigated when I said " check the rest of this circuit for obstructions". The exhaust elbow ( not sure of the design of this with two water entry points) might also be the problem.

 

[RichardS]

The 'interruption' is shown in the photo above. In the Volvo original the copper pipe on top of the engine is straight, from the thermostat to the manifold. In the photo this straight has been replaced by the one with the double elbows, with bracing between. The calorifier is connected between the two elbows. Volvo sell (or sold) a kit that added a pump and calorifier circuit to this engine, so I am not certain that the modification is theirs or not. The one in the photo appears to be DIY but I have seen others that were all green painted.

In your 2), assuming the calorifier hoses were blocked or airlocked, I believe that water would continue to flow along the perforated tube as there is no mechanism that would prevent this. In fact, if there was the engine would always overheat. Flow through the thermostat seems to be dependent upon the back-pressure developed by the three right-angled bends at the manifold, shown in my drawing at the end of the blue line.

Don't blame me for the engineering, I have been trying to puzzle it out for a long time and have reached these conclusions after lots of PMs from helpful Volvo users

Many thanks. I though that the bracing might be a balance pipe which is why "interrupted" left me none the wiser.

Anyway, we are clear that this is a total redirection. However, you and Vic seem to have a different opinion on the effect of a blockage in the calorifier piping and I don't have an opinion at all, which is unusual for me.

My "best" experience of parallel balanced flow systems versus serial flow came with working with domestic central heating installations in my houses in the UK and Russia. In the UK we use a balanced parallel system to connect the radiators to the boiler whereas in Russia they used a serial system. One system works well but is expensive whilst the other is cheap but appalling!

Richard

 

[saltyrob]

Hi ,

You guys are brilliant . Will read your posts again this afternoon and put a plan into action. Have found that there is gung in the cooling system so will also flush out with Fernox or similar . Also noted that the flange around the edge of the thermostat ,which sits in the groove in the rubber seal had corroded and started to disintegrate so may be worth checking.

Many thanks again

Rob

Rob

 

[vyv_cox]

However, you and Vic seem to have a different opinion on the effect of a blockage in the calorifier piping

No, I don't think so. A blockage of the calorifier or its hoses will cause the engine to overheat, because there is nowhere for the water exiting the perforations in the through-head pipe to go. Water would continue to flow through this pipe but it would not cool the engine to any extent. I also added an airlock in the calorifier loop as a possible cause because I have seen how remarkably effective one can be in preventing flow, particularly in this strange system that relies on back-pressure in one pipe to divert the flow into another.

 

[saltyrob]

Hi .

Couple of questions . What is the diameter of the copper pipe from the thermostat straight to the elbow . Also do the ends have raised diameters like a solder ring fitting to seal the pipe in the two end housings. Also to remove an air lock will attaching the dinghy pump to one end of the pipes to the calorifier do the job.

Cheers

Rob

 

[vyv_cox]

Hi .

Couple of questions . What is the diameter of the copper pipe from the thermostat straight to the elbow . Also do the ends have raised diameters like a solder ring fitting to seal the pipe in the two end housings. Also to remove an air lock will attaching the dinghy pump to one end of the pipes to the calorifier do the job.

Cheers

Rob

As far as I know it is standard 15 mm copper pipe. No idea about end fittings, depends who made it.

Best way to remove airlocks is to take off one or both of the hoses and back fill with water from a jug. You are trying to ensure that the whole of the water passage is full of water.

 

[RichardS]

I also added an airlock in the calorifier loop as a possible cause because I have seen how remarkably effective one can be in preventing flow, particularly in this strange system that relies on back-pressure in one pipe to divert the flow into another.

+1

Seen the same airlock issue in cars and hence suggestion in post #3 of "squeeze-pumping" the large diameter hoses as this sometimes clears it. I don't know whether it would work with boats or whether the hoses are flexible and long enough ...... probably not.

Richard

 

[VicS]

+1

Seen the same airlock issue in cars and hence suggestion in post #3 of "squeeze-pumping" the large diameter hoses as this sometimes clears it. I don't know whether it would work with boats or whether the hoses are flexible and long enough ...... probably not.

Richard

Which are these "large coolant pipes"/ "large diameter hoses" to which you refer ?

 

[RichardS]

Which are these "large coolant pipes"/ "large diameter hoses" to which you refer ?

The large diameter soft hoses on a car go to the top/bottom of the rad whilst the large diameter soft hose on my boat returns the coolant from the block.

I said at the start that I don't have a directly cooled engine so YMMV.

You'll have to be awake very early in morning to catch me out!

Richard

 

[bernie_ni]

sorry to hijack your thread a bit, Saltyrob - but does anyone know where to get that by-pass pipe from the thermostat to the exhaust elbow?
or should I maybe remove the existing pipe and ask a plumber to make up a bypass to the exact original length? I have not even seen a Volvo version and I shudder to think of the price
I would like to add a calorifier to my raw water cooled 2002 - but am in 2 minds. The engine is over 25 years old though it is still going reasonably well. just hard to start unless batteries are completely charged

cheers folks

 

[VicS]

sorry to hijack your thread a bit, Saltyrob - but does anyone know where to get that by-pass pipe from the thermostat to the exhaust elbow?
or should I maybe remove the existing pipe and ask a plumber to make up a bypass to the exact original length? I have not even seen a Volvo version and I shudder to think of the price
I would like to add a calorifier to my raw water cooled 2002 - but am in 2 minds. The engine is over 25 years old though it is still going reasonably well. just hard to start unless batteries are completely charged

cheers folks

When you see the price you will probably ask your friendly plumber to knock one up.

Sit down before you click the link!

http://www.marinepartseurope.com/en/volvo-penta-explodedview-7726000-90-11809.aspx