VP 2003 cooling system question.... Raw water cooled

[VicS]

If there is a good water flow with the thermostat removed but little or no flow with it fitted would I be right in assuming that there is no problem with strainer, hoses, pump etc or and that the problem lies with the "bypass circuit". (a new thermostat has been fitted)

Can someone explain what constitutes the bypass on these engines. I am more familiar with the MD11 etc where there is a small bypass built into the thermostat housing cover. On those that would be the first thing I would look at.

 

[chrisc]

or it is not getting hot enough to 'trigger' the thermostat

 

[andy_wilson]

Good flow where? Do you mean form the exhaust?

If this is a raw water cooled engine, when the engine is cold the thermostat should be closed and there should still be a strong flow to the exhaust. I'm not exactly sure how the water galleries work, but there is a part of the casting that sits beneath the thermostat that appears to allow cold raw water to blend with that already circulating as the 'stat begins to open.

It sounds like you need to de-crud the engine including thermostat housing and exhaust elbow.

I used brick and masonary cleaner on my VP 2002.

 

[VicS]

There must be a flow before the thermostat opens or the exhaust system will be damaged by the hot gasses before it does. Hence the little bypass built into the thermostat cover on the MD 11 etc.

 

[VicS]

[ QUOTE ]
but there is a part of the casting that sits beneath the thermostat that appears to allow cold raw water to blend with that already circulating

[/ QUOTE ] This is probably the part of the system I want to know more about.

At present there is no suggestion that the engine cooling system as a whole is in need of a chemical clean. That includes the exhaust elbow. There must be some local blockage or severe restriction that can hopefully be cleared without resorting to acid cleaning the whole lot.

 

[andy_wilson]

I had the 'benefit' of needing to get my cylinder head off, but there were a number of loose chunks of calciferous matter rattling around (and which wouldn't come out, that would not have been known about otherwise, though chemical cleaning addressed this).

Many promote the use of central heating de-scaler.

I used Brick and masonary cleaner (10% hydrochrolic acid) which I diluted 50:50, and dipped the thermostat, it's housing and the exhaust bend until the fizzing stopped and inspection yeilded clean shiny surfaces.

I used the time taken to get this result to soak the inside of the block for the same period.

First removed anode and drained down, flushed with fresh (not sea water 'cos I can't remember what (might) happen if you add Hydrochloric Acid to Sodium Chloride solution, but decided not to find out) down the thermostat hole. Replaced anode bolt, and drain plug and filled slowly with dilute Hydrochrolic acid, again through thermostat hole, waiting for fizzing to subside as I went.

Replaced exhaust bend and thermostat plus housing to rinse thoroughly after by running with the pump drawing from a freshwater bucket and no harm, only benefits, will come. Behold the thick milky solution being pumped out of the exhaust on rinsing.

Just noticed your bio. You should be cool with all this. Heating cleaner whilst more expensive, contains chemical buffers, probably to protect ali/alloy castings in boilers. Dil HCl acid has no such luxuries, but makes the bronze and copper bits shiny and returns the iron casting to a dull grey finish. I think it would get to work on the copper if left too long, hence the need for a good rinse.

 

[Rustyknight]

There's two old threads HERE and HERE that might be of help.....


I'll expand a little, just in case it's too much trouble following the links /forums/images/graemlins/wink.gif

The raw water from the impellor pump runs through an alloy pipe that goes through the engine block. Depending on the engine size (2001, 2002, etc) this pipe has a hole drilled in it (more than one possibly for the bigger engines) which allows cold water into the block as and when the thermostat opens.

If the thermostat is closed, the water goes straight to the exhaust elbow without entering the block..... as and when the thermostat opens, the hole allows water to be drawn into the block, thereby cooling the head.

It's not unknown for the hole in this tube to get either partially or fully blocked due to a build up of cruddy limescale like deposits..... stopping the water from entering the head, but allowing shedloads of water to go into the exhaust as normal. Thus, the flow of water appears normal, even though the engine overheats.

It's quite a simple job to strip down and renew the pipe, not forgetting to get loads of washers and seals to replace the old. Best to nip down to your local Volvo dealer who can show you the parts on their 'puter, with an exploded diagram of how it fits together.

 

[VicS]

Andy,

I am one of those who would prefer sulphamic acid, or even if scaling was not too severe citric acid, based central heating boiler descalers. I would be afraid that a strong acid such as hydrochloric acid could do some damage especailly if it was left in for too long, not neutralised or flushed out thoroughly. The copper bits would be the last of my worries. Although dilute HCl does attack copper in the presence of oxygen in a dissimilar metals situation it would be the iron that is attacked preferentially. Aluminium bits and anodes would be attacked the fastest and preferentially to the iron. A proprietary central heating descaler might be more expensive than brick cleaner but in comparision with the other costs of boat ownership the price of a tub of Fernox DS-3 is nothing.

I certainly would not use hydrochloric acid in any greater concentration than you suggest and would err on the cautious side and probably use it a little more dilute. When used industrially for acid cleaning an inhibitor may be added to the acid which limits the attack on the metal. I must confess my experience of acid cleaning is limited to large steam raising plant and even that was 30 years ago and more but it was done under careful supervision.

Nothing will happen if you mix hydochloric acid with sodium choride, you probably have in the back of your mind the production of chlorine if any acid is mixed with a hypochlorite based bleach.

 

[VicS]

Rustyknight,

I have looked at the links, thanks.

However the problem I describe is not the same. I am talking about a situation in which there appears to be a good flow from this distribution pipe into the engine, as there is a good flow when the thermostat is removed, but there is little or no flow when it is in place. More or less the opposite situation in fact. Somewhere there must surely be a deliberate restriction near the end of this pipe (which has now become almost totally blocked) or there will a poor flow through the engine even when the thermostat opens. It's the normal "shed loads" of water going directly to the exhaust that is missing!

However I am beginning to have some idea where the problem must be.

 

[Rustyknight]

Hah! That'll teach me to read a post too quickly without my contact lenses in.

I'm probably close though, just arse about face! It shouldn't be too much of a job to disconnect the water distribution pipe at both sides of the block and investigate from there....... either with a piece of wire of a long thin screw driver. If thats no better, then track up to the exhaust elbow.

 

[nigelhudson]

From memory and a quick look at the parts list I suggest the following.....

Remove the pipe that links the exhaust elbow and the back of the cylinder head (not the one that links the thermostat housing with the elbow). Then remove the anode plug at the front of the engine. You should now be able to access both ends of the water distribution pipe mentioned in the earlier post. If you poke through with a length of wire you should be able to ensure the pipe is clear of crud. Reassemble and see if you get full flow.

 

[Rustyknight]

[ QUOTE ]
Then remove the anode plug at the front of the engine.

[/ QUOTE ]

Not sure why the anode plug needs removing..... isn't the water distribution pipe just below this? Just the rubber hose from the water pump/anti-syphon valve, and then a small elbow need removing at the front end. (On the 2001 at least)

 

[Juggler7823]

You say "If the thermostat is closed, the water goes straight to the exhaust elbow without entering the block..... as and when the thermostat opens, the hole allows water to be drawn into the block, thereby cooling the head." I don't understand this. the water will still pass through the holes in the circulation tube and also I cannot see any pipe connecting to the exhaust elbow. On my engine the circulation pipe just ends with a seal and blanking plug. Unforetunately the parts catalogue that someone provided the URL for mentions the bypass components on page 590 but this is not part of the scanned file.

I think this bypass is the source of this problem

 

[ruvane]

Be careful with following the parts catalogue blindly. I have an MD11 and have the same blind hole in the thermostat housing, even though the drawings show a through-pipe. If there was something fundamentally wrong I would have expected it to show up in the 30 years it's been running!

I had an overheating problem and it was due almost entirely to blocked pipes.

 

[EdEssery]

Done that job. You don't need to replace the pipe through the block, just remove it, clean it with kettle descaler, possibly drill the hole(s) out to make them bigger and reassemble.

Remove the external pipes leading to the front of the block and from the back of the block to the water injection elbow (Volvo 2001).

Select a deep spanner socket (or equivalent) to use as a drift. This needs to be smaller than the hole in the front of the block but larger than the pipe you are trying to knock out that you will be able to see through the hole in the block. Use the drift to knock the transfer pipe out of the block from the front towards the back. You will find that the pipe has a flange on the rear side which means it can only come out from front to back. Once the flange is clear of it's recess in thye back of the block, it should pull out easily. The flange has a rubber sealing ring on it, I would consider renewing this if there is any damage to it or any evidence of water leaks down the back side of the block. The necessary sealing ring is in the Water Seal replacement kit available from Keyapst and others for about £10. I used the opportunity to relace all the sealing rings on the engine cooling system.

As the pipe comes out, notethe orientation of the pipe vis a vis the (possibly blocked up) holes in it. It needs to go back in the same way. The pipe on a 2001 has a single hole oriented (from memory) in the six o'clock position but don't hold me to that. I understand the pipes from the 2002 and 2003 have multiple holes and that they are not in line with one another.

It's a pretty easy job if you're reasonably practical.

Ed

 

[Rustyknight]

Agree that the old one can be re-used, as long as the drift chosen to knock it through doesn't damage it too much. When I did the job, I bought a new one before starting taking things apart, as I didn't fancy the hassle of putting it back together and finding it leaked.

Still, I now have a spare!

Quite correct as well where you say on the 2001 the hole in the distribution pipe should be in the 6 O'clock posistion. In all the manuals I have for the engine, it's the only mention the thing gets!

 

[paulwitney]

I don't know if you have found a solution yet but on my 2002 the blockage was in the bypass pipe to the exhaust elbow. Comes from the rear of the block up to the the exhaust elbow. At the engine end there is a nylon "washer" restictor and this was clogged with calcium. Poked out gunk with a small screwdriver and all was well.
Another separate problem is scale build up in the exhaust elbow but that would cut flow at all times. Have cleaned mine out but is due for another "service" now. Removed it and soaked it in washing soda solution for few hours (half a cup of crystals to 2 litres of near boiling water) then used a piece of wire in a drill to remove stubborn stuff. Also had to remove welsh plugs either side to get to all areas. Total repair cost about $6 ......... beats buying a new exhaust elbow!!!!

 

[Juggler7823]

I've just returned from the boat and read Pauls note. Its a pity I did not read it before I went! I was convinced that the problem lay in a blocked bypass and Paul and I was correct. So was the person who said that there was a pipe at the rear of the engine. I did find a copper pipe exiting at the rear of the engine and connected to the exhaust elbow. I have never noticed this before!. I did not see a nylon restrictor but will look again. Does anyone have a copy of page 590 of the Volvo parts manual which details the components of the bypass system? On removal, the end into the elbow was virtually blocked with carbon and scale, easily removed with a screwdriver. I now get a good flow even when the engine is cold. Problem solved!!!!!! I am sure that the elbow needs removal for descaling but did not have a gasket. Thanks to all who responded especially VicS. Everyones help was invaluable.