Overheating MD11C, how easy is to remove the exhaust manifold & start cleaning

CAPTAIN FANTASTIC

CAPTAIN FANTASTIC

Well-Known Member
Joined
15 Jul 2009
Messages
3,311
Location
Bristol Channel
Visit site
My Volvo MD11C has been working trouble free but this season the operating temperature is higher (not in the red region yet) and there is less water coming out from the exhaust pipe; it is a raw water cooled engine.

I fitted a new water pump impeller, although the old impeller looked good condition, there is no restriction from the water intake to the pump, I therefore need to start looking for any problems from the water pump all the way to the exhaust pipe.

Tomorrow, I will remove the exhaust manifold to make an attempt to descale the water holes and jackets to allow water flow (provided there is scaling that is causing the problem; cant be anything else).

How easy is to remove the exhaust manifold and do the cleaning? anyone done it recently? I will also check the thermostat before dismantling too much.
 
Last edited:
CAPTAIN FANTASTIC said:
My Volvo MD11C has been working trouble free but this season the operating temperature is higher (not in the red region yet) and there is less water coming out from the exhaust pipe; it is a raw water cooled engine.

I fitted a new water pump impeller, although the old impeller looked good condition, there is no restriction from the water intake to the pump, I therefore need to start looking for any problems from the water pump all the way to the exhaust pipe.

Tomorrow, I will remove the exhaust manifold to make an attempt to descale the water holes and jackets to allow water flow (provided there is scaling that is causing the problem; cant be anything else).

How easy is to remove the exhaust manifold and do the cleaning? anyone done it recently? I will also check the thermostat before dismantling too much.
Click to expand...

No problems removing the exhaust manifold as far as i can remember so long as all the bolts (8) come out without difficulty

You'll probably find that the small passages from the inlet on the underside to the cyl heads are well choked up. One ( rear IIRC) is longer than the other so tends to be the worst.

BUT restrictions here, or anywhere else through the engine itself, wont affect the total flow out of the exhaust.......... check particularly the inlet into to the exhaust bend! . and the bypass in the thermostat cover... also all the hoses


Probably worth checking the injection point into the exhaust bend before going any further
 
There is info here: http://www.westerly-owners.co.uk/woaforum/viewtopic.php?f=2&t=2851

It sounds like you have started at the inlet seacock and strainer and worked towards the water pump, just eliminate posibilities until you find out what's up.

I found that measuring the cooling water flow helped me get my head round what was happening.

The exhaust mixer elbow blocking seems to be a popular culprit, and is easy to get off and poke, as VicS said above, so I would try that before the exhaust manifold.
 
Oh and BTW

when you take the cover off the thermostat you will find a small passage with an O ring seal around it in the cover .......... it does not mate up with a passage in the manifold. Don't try to unblock it... it is not there!
 
VicS said:
Oh and BTW

when you take the cover off the thermostat you will find a small passage with an O ring seal around it in the cover .......... it does not mate up with a passage in the manifold. Don't try to unblock it... it is not there!
Click to expand...

Thanks for the tip; I red some stories of people accidently "creating" new water passages.
 
Have you checked the impellor cover plate and back plate for wear? On a recent trip to collect my father's Centaur the temperature gauge started to head towards the red, we stopped in Salcombe and took the cover and impellor off. The only thing we could see wrong with it was some light scoring on the cover plate. We fitted a replacement impellor and a new cover plate that we had spare and the difference was amazing! Pumped so much more water than before even at idle and the temperature gauge didn't go above 1/3 for the rest of the journey.
 
Big-Bang1 said:
Have you checked the impellor cover plate and back plate for wear? On a recent trip to collect my father's Centaur the temperature gauge started to head towards the red, we stopped in Salcombe and took the cover and impellor off. The only thing we could see wrong with it was some light scoring on the cover plate. We fitted a replacement impellor and a new cover plate that we had spare and the difference was amazing! Pumped so much more water than before even at idle and the temperature gauge didn't go above 1/3 for the rest of the journey.
Click to expand...

Yes, there is scoring on the plate, I intent to reverse the plate and see the difference.
 
I removed the exhaust manifold and found that some waterways were totally blocked with hard carbon and calcium deposits as hard as concrete. I placed the exhaust manifold inside a plastic bucket and filled it with Domestos Zero Limescale which is a solution of hydrogen chloride and sulphamic acid. It was bubbling for about one hour and removed all hard calcium including oily dirt. The waterways are all clear now and water is flowing again.
20150426_171324[1].jpg
 
CAPTAIN FANTASTIC said:
I removed the exhaust manifold and found that some waterways were totally blocked with hard carbon and calcium deposits as hard as concrete. I placed the exhaust manifold inside a plastic bucket and filled it with Domestos Zero Limescale which is a solution of hydrogen chloride and sulphamic acid. It was bubbling for about one hour and removed all hard calcium including oily dirt. The waterways are all clear now and water is flowing again.
View attachment 51212
Click to expand...

That's basically what I was going to say. After many years of keeping an old MD17C running I know a few tricks. We used to soak our old manifold for days in vinegar and use a variety of tools to keep the passages clear.
One other thing on the MD17C was that if you had an impeller fail then the pieces of the impeller could become lodged in a T piece under tha manifold which would cause wildly fluctuating temperatures as the rubber bits moved about. I'm not sure if the MD11C has the same T piece under the manifold but if you do then it's a good place to look in similar circumstances.
 
If I take the trmperature sender out of the top of the exhaust manifold to get some descaler in, how worried should I be about fluids getting back into the exhaust ports?

As I understand it the water gallery is a different bit of the exhaust manifold and it would be difficult, but not impossible, to get stuff back into the cylinders.

I tried it before but it was already flooded with water and I couldn't get much oxalic acid solution in before it overflowed, I supose that is where the drain cock on the maniflod has it's uses.
 
aquaplane said:
If I take the temperature sender out of the top of the exhaust manifold to get some descaler in, how worried should I be about fluids getting back into the exhaust ports?

As I understand it the water gallery is a different bit of the exhaust manifold and it would be difficult, but not impossible, to get stuff back into the cylinders.

I tried it before but it was already flooded with water and I couldn't get much oxalic acid solution in before it overflowed, I suppose that is where the drain cock on the manifold has it's uses.
Click to expand...

The only route by which water can get to the exhaust gas side is via the hose from the top of the thermostat housing to the exhaust outlet bend. Disconnect the hose and the possibility is eliminated.


Drain the system first, ensuring that both cylinder blocks drain via their respective drain cocks and that the manifold is drained via its drain cock.


I'm not sure that you will achieve very much especially in the main areas that scale/ block, namely the water inlet channels in the manifold and the cylinder water jackets. What you suggest may help to clean the outlet channels in the manifold and the cylinder heads.

The cylinder water jackets are the worst parts to clean. Can be done to some extent if the blocks are removed but in severe cases may require the liners to be pressed out.
 
I am going thru same issues with my Centaurs MD11C.

Have eliminated inlet strainer, changed impeller and have ordered new temp sensor and thermostat. I now have the manifold off and it is solid, so think it may be the culprit. I will do as Capt Fantastic and clean it. However, the waterways on the engine side are also totally blocked (how she ran last year i don't know)... question is can I have a go with a screwdriver etc to try and get get a bit of flow then rig up a fernox cleaning system 12v pump etc.

Also one nagging thought can the manifold become so corroded inside it becomes unserviceable and if so were to source another?
 
No problem with removing the manifold, you will probably find that most of the waterways are blocked with a very hard deposit which is best removed using an electric drill.

If you are using Volvo hose between seacock & gearbox, within the cooling system - it is not uncommon for this hose to suffer from internal failure which blocks the waterflow when revs are well above tickover, but the hose allows water to pass at low revs. For very little money a hose renewal is a good investment.

For my MDIIC, a home made fresh water cooling system absolutely revolutionised the engine, no more cooling blockages or leaks, quick warm up, better fuel consumption etc. Approx £40 spent & worth every penny.
 
i have had my manifold off MD11C and after 2 hrs in descaler solution got clear water running out of all correct ports except the inlet channel furthest from the thermostat, any ideas on clearing this, it seems the "blockage" is between the T bar inlet underneath the manifold and the manifold inlet channel.
 
Been there (last year) going like a racehorse now!

grunter10 said:
i have had my manifold off MD11C and after 2 hrs in descaler solution got clear water running out of all correct ports except the inlet channel furthest from the thermostat, any ideas on clearing this, it seems the "blockage" is between the T bar inlet underneath the manifold and the manifold inlet channel.
Click to expand...

The one thing that people tend to forget is the water jacket around the gear box that has water sucked through it by the pump before entering the engine. Ours was full of ferous oxide (is that right?) and salt it was completely blocked - we cleared it by running a drill backwards with a piece of rigging wire into each of the the three accessible holes and then jet washing back out of the water inlet (we were ashore).

We replaced the head gasket and cleared the water ways (my mate is quite good at this kind of thing)

The elbow is rubbish - hard to clear but an easy job to get on and off. The thermostat can gunk up and the impeller housing pump has been replaced.

Apparently there is a new substance on the market "salt away" or similar. Some of the acidic central heating solutions can apparently damage some metals, this one cannot. Not used it personally though.

Got the water running, now the diesel is draining back away from the injector pump making it a nightmare to start. Happy days.

Having done all of the above I can't tell you what worked and what was unnecessary.
 
maxi said:
For my MDIIC, a home made fresh water cooling system absolutely revolutionised the engine, no more cooling blockages or leaks, quick warm up, better fuel consumption etc. Approx £40 spent & worth every penny.
Click to expand...


For £40 or £50 I'd have a go at changing mine over, come on Maxi - let's have a how to with pictures :-)
 
CAPTAIN FANTASTIC said:
I removed the exhaust manifold and found that some waterways were totally blocked with hard carbon and calcium deposits as hard as concrete. I placed the exhaust manifold inside a plastic bucket and filled it with Domestos Zero Limescale which is a solution of hydrogen chloride and sulphamic acid. It was bubbling for about one hour and removed all hard calcium including oily dirt. The waterways are all clear now and water is flowing again.
View attachment 51212
Click to expand...

Today I descaled the rest of the cylinder head water jackets by pouring descaler into the voids. I tried a very expensive purpose made marine descaler with average results, I then used Domestos Zero Limescale and the results were great, and much better than the other product; £2 per bottle.

I put everything back and started the engine; after one hour of motoring at high revs, the engine temperature was quarter way up the green region and plenty of water out from the exhaust.

The thermostat looks very poorly, so I am looking to replace it, does anyone know a part number equivalent from Halfords?
 
You must log in or register to reply here.

Share this page

Top