VP 2003 thermostat and cooling/hot water

[chris-s]

Oh the joys of a new-to-us boat!

So, said boat has a raw water cooled VP 2003, first inboard engine for us. This weekend saw us use the motor for something other than just on/off the mooring, a half hour motor. When we got back to the mooring we thought this would be a great opportunity to check the calorifier for hot water... but nope, it was cold.

Before launching we fitted a new impeller, it's pumping fine, plenty of water thru the exhaust system and the Silicon Marine exhaust temperature monitor shows no issue.

Symptons....firstly, the pipes to/from the calorifier were cold, so this suggested that no water was exiting thru the thermostat. I'm not sure how hot the engine block should be or was, but it was uncomfortable to keep my hand on the rocker cover. No water temperature alarm sounded.

This evening I removed the thermostat, the water galleries underneath it were pretty much empty ie the thermostat was not sat in any water, neither was the temperature alarm sensor. I removed the anode bolt and water emptied out. The distribution/bypass pipe was not obstructed and using my endoscope I could clearly see the perforations in it were clear.

I blocked the bypass pipe exit on the rear of the engine and then poured some descaler into the raw water inlet pipe at the front of the block. With no problem, the block filled right up to the thermostat housing, fizzing away. I took this to indicate that there aren't any serious blockages in the bypass/distribution pipe or throughout the rest of the block.

I let the cleaner sit for best part of an hour and then replaced the thermostat housing (without thermostat but a home made gasket) disconnected the calorifier return pipe and pumped thru fresh water to flush out the cleaner. No issue, the mucky water freely flowed out into a bucket. So now i have water flowing freely from inlet to calorifier outlet. I only had a half-litre of cleaner so will repeat this and set up a pump to cycle it.

So, no blockages. The thermostat appears to be in pretty good condition and whilst I do have a new spare one, I thought I would test it to check its opening correctly. With it suspended on a piece of thread in the wifes best pasta pan, it fell off at 61degrees, appeared fully open around 75 and closed up again around 60. So thats all good and I will probably fit the new one anyhow just for peace of mind, after checking it opens at the correct temperature.

Feeling a bit stumped now, the only thing I can think of, after seeing what must be a bleed point on the thermostat housing, is maybe there was an airlock under the thermostat which kept it out of the water and meant that it wouldn't reach temperature to open. The temperature sensor would most likely also have been out of water to. I'm pretty sure that the thermostat should have a small bypass hole or something to allow it to bleed thru, is that right? Is it typical to have to open the bleed nipple on the thermostat housing? Any other thoughts?

Chris

 

[scottie]

The raw water cooled engine uses a lower value thermostat as running hot salt water is not good practice and will give at best warm water
as there is no closed circuit there is minimal rise rise in temperature and you are using cold water at all times

there were flow reducers available at one time may still be some about
it may be worth checking the the cooling tube in the head as it has flute style jets to cool the injector copper sleeves
if you decide to take it out to check or clean mark it first so that the holes Aline properly and one end has a distinct bellmouth so watch way yo drive it out with a wooden plug
change as many seal rings as you can while you are at it

bear in mind it’s now quite an elderly engine and as you are doing other thing’s check the exhaust elbow for corrosion

 

[VicS]

The thermostat is opening at the correct temperature for a raw water cooled engine. . . . Is it installed correctly .... sensing bulb down .... ?

Is the water distribution pipe installed correctly (probably not the answer to the problem but would affect cooling}

I don't believe the lack of a bleed hole in the thermostat is the cause of the problem. It would be common problem if it was.
(The "bleed nipple" is the blanked off position for a vent to the header tank in a freshwater cooled installation}

I suspect that the calorifier is the cause of an air lock. make sure all the air is bled from the heating coil and the connecting hoses.

 

[chris-s]

Just a follow up…after a short motor yesterday we had ‘warm water’ in the calorifier, so I’m taking that as a success that all is good…until I see otherwise.

After setting up a recirculating bucket and pump with the thermostat removed and the bypass pipe outlet-to-mixer elbow blocked off, I ran 5 litres of pro-flush thru it for a couple of hours. I also had 5 litres of vinegar but it wasn’t really enough as by the time I added water to fill the system it was too dilute (I think).

I couldn’t remove the bypass tube without removing some cabinetry in the aft cabin but using my endoscope before and after the improvement was clearly visible.

The mixing elbow was new last season, so have left that be for now.

Judging from the mucky state of the water it will certainly benefit from further cleaning but perhaps I can use something more economical than pro-flush next time.





Thanks for the advice.

Chris

 

[AntarcticPilot]

I have the same setup - raw water cooled VP2003 with calorifier.

Half an hour is nowhere near enough time to heat a tank of water; it might get slightly lukewarm, but not hot. The engine is very slow to heat up, and until it reaches full operating temperature, it won't heat the water at all. I know my thermostat is fine; I tested it in a pan of hot water. If you'd run the engine for an hour or so I might be concerned.

 

[scottie]

I suspect that you unfortunately will discover that the only way to a more quickly available quality of more than tepid water from your 2003 is to fit freshwater cooling just as many many owners did so when the 2000 series was a current unit to the extent that as a VP dealer we kept a kit on the shelf in stock which we only did for items that sold
the engines were supplied by VPUK as raw water cooled and converted by dealers
the most efficient way might be an inverter and electric kettle

 

[AntarcticPilot]

I suspect that you unfortunately will discover that the only way to a more quickly available quality of more than tepid water from your 2003 is to fit freshwater cooling just as many many owners did so when the 2000 series was a current unit to the extent that as a VP dealer we kept a kit on the shelf in stock which we only did for items that sold
the engines were supplied by VPUK as raw water cooled and converted by dealers
the most efficient way might be an inverter and electric kettle

Actually, you can get water that is just too hot to hold your hand under from a raw water cooled VP 2003; I do. But it does require quite a long period of running - in and out of the harbour won't do it.

 

[wicked]

Sounds like you have the classic raw water cooled VP2003 with calorifier - symptoms are usually engine overheating, no hot water in calorifier or only tepid hot water.

The reason for this is that the calorifier introduces additional friction in the water circulation.

What is supposed to happen is that when starting from cold, the cooling water goes straight through the flute tube and into the elbow to cool it. When the thermostat opens, the water can flow into the block through the little holes in the flute tube, then round the cylinders etc. and out through the exhaust waterways.

With the calorifier in circuit, you usually find that the additional friction causes the bulk of the water to continue to flow straight through the flute tube.

The answer is a small flow restrictor which fits into the rear end of the flute tube. There doesn't seem to be a Volvo part number for one but they are really easy to make, and immediately cured all the issues on my V|p003 - with plenty of hot water from the calorifier and no more engine overheating. These restrictors often get lost when exhaust elbows are changed.

To fix mine I purchased a short length of 12mm diameter nylon rod from eBay. Saw off a length 14mm long (no longer - but a bit shorter would be ok). Drill a 6mm diameter hole through the middle.

Remove the copper tube which goes between the back end of the flute tube and the exhaust elbow.

The nylon restrictor should push easily into the flared rear end of the flute tube. It will only go in a little way - which is why it must be no longer than 14mm or else the pipe won't re-seal. Refit the pipe.

Hey-presto - all now works fine - still getting plenty of exhaust coolant water through before the thermostat opens, and when it opens there is now coolant flow through the engine and calorifier heating the water.
Hope this helps. Dave

 

[chris-s]

Thanks for the tips. After some more motoring today it looks like any cooling issues have been resolved, and whilst the water might not get piping hot, to have pumped water alone is a luxury as it is coming from our previous boat.
I will make up one of those restrictors and keep it on hand just in case.

Chris