Best chemicals for flushing a raw water cooled Volvo Penta?

[mikejakes]

I've got a raw water cooled Volvo 2003 and it's been overheating due to a build-up of silty sediment in the block. A mechanic has used Spirit of Salts (hydrochloric acid) to try to shift what he described as a slimy grey sludge as seen through the block drain hole at the back of the motor, starboard side but I'd like to flush the block a few more times to try to ensure that it's completely clear. As I really don't fancy the alternative of removing and strippping the engine for a manual clear-out, what has been used successfully to get rid of crud like this from the block? (For info, I have confirmed that the water pump and thermostat are working correctly and that the water distribution pipe, exhaust elbow and associated external pipework are all clear). I suspect that converting the engine to fresh water cooling will be cost-prohibitive.

Also, can anyone recommend a raw water strainer that will still allow an appropriate bulk flow of raw water yet filter out particles smaller than the footballs my existing one lets through?

Thanks in Advance
Mike

 

[VicS]

Hydrochloric acid is just about the most aggressive thing you could use. Something I'd use with some caution.

more gentle alternatives are RYDLYME and a sulphamic acid based boiler descaler such as Fernox DS-3

 

[mattnj]

i did this a while ago....with a mix of Oxalic Acid and vinegar, (look on Ebay for the acid) got a few 5L containers of vinegar from Tesco, then ran the engine, and let it sit full of my mix for a couple of days, and ran it again, a load of crud came out..

 

[saltyrob]

Hi,

I intend to use Fernox DS-3 as it seems to be less aggressive and thus reduce potential to damage the engine than some stronger acids.My plan is to pump it into the engine via the cooling pipe from the inlet strainer to the gearbox, rather like filling with anti freeze for winterization, and leave for an hour or so.Can you confirm if this method is ok or is there a better way of doing it.

Many thanks

Rob

 

[VicS]

Drain every thing down beforehand. Perhaps remove the thermostat too.

Sulphamic acid is the strongest of the so called weak acids, stronger than all the organic acids such as acetic ( vinegar), oxalic, citric etc but is nowhere near as strong as hydrochloric acid..
Being a weak acid it will react with scale etc relatively slowly unless used warm. Try to use it warm if possible, maybe it'll even be possible to warm the engine up before hand other wise be prepared for it to take a while.

 

[vyv_cox]

Hi,

I intend to use Fernox DS-3 as it seems to be less aggressive and thus reduce potential to damage the engine than some stronger acids.My plan is to pump it into the engine via the cooling pipe from the inlet strainer to the gearbox, rather like filling with anti freeze for winterization, and leave for an hour or so.Can you confirm if this method is ok or is there a better way of doing it.

Many thanks

Rob

There is not much in an engine that will be affected by brief (an hour or so) exposure to HCl. Zinc anodes and brass thermostats will, so they should be removed. Copper and paper gaskets will be OK. Nitrile rubber is affected long term by concentrated HCL, not by dilute. I would not be very concerned about using it.

Fernox is designed to circulate, hot, through central heating systems. You will have better results if you can arrange this somehow. If the boat is ashore it's easy, catch the coolant coming out of the exhaust in a bucket or cut-down plastic drum and put the pump suction hose into it. If afloat it takes a bit more ingenuity. You need to detach the water hose from the engine at the exhaust manifold, extend this with another hose and take this to a bucket in the cockpit. Now add a hose on the suction side of the pump and take this to the same bucket. You can now circulate the Fernox through the engine. With judicious baling you should be able to keep this going for half an hour or more, until the solution gets close to boiling.

While all this is going on your exhaust will be uncooled and will catch fire. So you need to arrange a hose pipe to the exhaust manifold, not turned on so hard that it will backfill the engine. Try to match the flow that normally comes from your exhaust.

I must say though that if HCl has not fixed the problem it is unlikely that anything else will do it, unless you have some unusual deposits in there. In the past I have found a mixture of salt and carbon in very small coolant passageways, which would resist HCl but possibly not Fernox. In my case a twist drill solved the problem.

 

[Peegee]

I do it my way!

I have no doubt that I will be shot down in flames and totally disagreed with, BUT.......
In the past whenever I have tried to drain my block (VP2002) I have gone so far as to completely remove the drain tap assembly from the block, and still had no flow!
I made up a "prodder" from a stainless bike spoke with a "T" handle to give a good grip and a sharpened point on the end. The first time was real hard work winding away into the block untill eventually it gave with a gush and the block drained.
Subsequently at end of season drain it is now easier, but still needs a "prod" to clear the hole.......Having had the head off in the past I can vouch that the problem is more to do with the fact that the drilling in the block is quite small and angled up into the lowest part of the water jacket. What hapens is that all the crud (mostly silt in my case) just fills the drilling and consequently settles to an almost solid plug.
Once you "prod" through the plug you find the water just gushes out bringing any other crud with it.
Hope this helps
Peegee

 

[saltyrob]

Hi

Can you confirm where the drain tap is on the VP2002 block and what is required to undo it.Manual is on boat and info would be useful. I have heard of solution being circulated through the engine with an electric pump,any mileage in this.

Many thanks

Rob

 

[Peegee]

Hi Rob
Its just below the starter motor on the left hand side of the engine looking from the front.
It consists of a two piece brass "spigot" The front part should be able to be undone and then it will drain....thats the theory!. However as I said in the previous post, its easier to totally unscrew the front piece and then remove the block part from the block so you can get a good "poke" into the block. Can't for the life of me remember what size spanner...think its 14mm...It helps if you have a stubby spanner as there is not a heap of room.
Peegee

 

[Piers]

I've used Rydlyme (Marine versions) very successfully. No damage to the metals at all. Just remember to remove any zincs first otherwise the Rydlyme will eat tem as ewllas the limescale.

 

[saltwater_gypsy]

Don't fool around, do as the Med. fishermen do .....use Original Coca Cola.
It believe it has a good concentration of oxalic acid and some other useful toxins.

 

[VicS]

....use Original Coca Cola.
It believe it has a good concentration of oxalic acid and some other useful toxins.

I hope not! Citric acid and some phosphoric acid I believe.

Sulphamic acid, as Fernox DS3 should be quicker acting, at least on limescale. Maybe something containing a high citric acid concentration will be more effective on rust. etc.

Rydlyme remains a bit of a mystery to me. I reckon it must be hydrochloric acid plus salts of organic acids to raise the pH.
Pity I cannot now get some into a lab to take a closer look.

 

[Nina Lucia]

Hi, I had the same problem with my 2002, tried descaling, but didnt work, on the the end I just clened heat exchanger, I have used coat hunger to pokit out and now works perfectly!
Volvo even told me to take heat exchanger out and make little bit biger hall.........
Took twenty minutes, and its realy working fine....

 

[SimonD]

Hi

I have heard of solution being circulated through the engine with an electric pump,any mileage in this.

Rob

Hope so! I've just ordered one of those little pump jobbies that's powered from an electric drill. Wolfcraft pump on Amazon at about £7. It looks pretty much like the jabsco pump on the engine, so should do the job. If you want to circulate the solution hot, is there not an immersion heater designed to go into a cup. Camping and caravanning shops should sell such a thing. Sounds a lot easier than running the engine with elaborate recyling bits and bobs and a burning exhaust!

 

[saltyrob]

Hi,

Did you circulate the Rydlyme or pump it into the engine and leave it to do its thing.

Rob

 

[SimonD]

Hi,

Did you circulate the Rydlyme or pump it into the engine and leave it to do its thing.

Rob

Haven't tried it - waiting for the pump. However, I plan to pump it round, leave for a bit, pump round again etc. Can't see the point in constant circulation.

 

[pampas]

remove any annodes(Engine) and sea water pump impellor. sea suction into bucket, exhaust injection pipe into bucket, drill pump on sea suction, partially fill bucket(Fresh water) and turn on pump until a good flow rate is acheived. add correct amount of Rydlyme run until solution is spent. reconnect everything and start engine, job done. I do this every other year and Rydlyme does what it says on the tin. Visit there site and see the reuslts. Satisfied customer only.

 

[cliff]

I just gave my DV24 its annual internal clean using Fernox DS-3 central heating descaler - works a treat.

I put a bucket in the cockpit and ran a hose from it to the cooling water (raw) on the engine, filled the bucket with fresh water and ran engine, topping up the bucket with more fresh water as needed. Once the engine had run at normal temp for about 10 minutes I placed another bucket below the exhaust to catch the discharge and used a small inline pump to pump this discharged water back to the bucket in the cockpit. I then added the "fernox" to the bucket in the cockpit and continued to run the engine under load (well tied to the pontoon) until it was "hot", topping up with fresh as needed. Within a few minutes the water went black as the crud was dissolved and washed out. I continued to circulate the coolant for about one hour adding another bottle of fernox to compensate for losses at the exhaust.
Result was one very clean engine which heats the calorifier much better than before and no longer "overheats" on full power.

It helps to remove the stat after the fresh water flush so there is a good flow through the block / head. As one is recirculating the coolant the engine will warm up even without the stat.

"Fernox" is available from plumbers merchants or B&Q for 2~3 times the cost from a plumbers merchant

 

[mattnj]

Hi, I had the same problem with my 2002, tried descaling, but didnt work, on the the end I just clened heat exchanger, I have used coat hunger to pokit out and now works perfectly!
Volvo even told me to take heat exchanger out and make little bit biger hall.........
Took twenty minutes, and its realy working fine....

dont think he has a heat exchanger on the raw water cooled one...

 

[vyv_cox]

I just gave my DV24 its annual internal clean using Fernox DS-3 central heating descaler - works a treat.

I put a bucket in the cockpit and ran a hose from it to the cooling water (raw) on the engine, filled the bucket with fresh water and ran engine, topping up the bucket with more fresh water as needed. Once the engine had run at normal temp for about 10 minutes I placed another bucket below the exhaust to catch the discharge and used a small inline pump to pump this discharged water back to the bucket in the cockpit. I then added the "fernox" to the bucket in the cockpit and continued to run the engine under load (well tied to the pontoon) until it was "hot", topping up with fresh as needed. Within a few minutes the water went black as the crud was dissolved and washed out. I continued to circulate the coolant for about one hour adding another bottle of fernox to compensate for losses at the exhaust.
Result was one very clean engine which heats the calorifier much better than before and no longer "overheats" on full power.

It helps to remove the stat after the fresh water flush so there is a good flow through the block / head. As one is recirculating the coolant the engine will warm up even without the stat.

"Fernox" is available from plumbers merchants or B&Q for 2~3 times the cost from a plumbers merchant

That's how I used to do it with the boat ashore. Afloat, the exhaust discharge is about 2 inches above the water, so no room for a bucket. Hence the more complex method I suggested above. I never needed the extra pump, just took a hose from the raw water pump straight to the bucket.