Volvo MD2020 Coolant Flush

steveej

steveej

Well-Known Member
Joined
27 Mar 2014
Messages
538
Location
Bristol
Visit site
Ok so on the boat today and overheat alarm goes off again.

I want to drain the coolant and flush it a few times tomorrow.

Problem number one, the drain plug is square and none of my sockets fit. Can’t get an adjustable in there as not enough space. Is there a special tool? Has anyone else managed to sort this.

The paint was completely undisturbed so would not surprise me if it’s never been flushed.
 
steveej said:
Ok so on the boat today and overheat alarm goes off again.

I want to drain the coolant and flush it a few times tomorrow.

Problem number one, the drain plug is square and none of my sockets fit. Can’t get an adjustable in there as not enough space. Is there a special tool? Has anyone else managed to sort this.

The paint was completely undisturbed so would not surprise me if it’s never been flushed.
Click to expand...

The coolant should have been drained and changed every 2 years .... possibly bad news if that has not been done as it could be contaminated with seawater :(

Also the heat exchanger seawater side should have been cleaned regularly.

Consider also that the water injection point into the exhaust may be restricted

I'm assuming you have checked or changed the seawater pump impeller and that the inlet strainer is clear

Drain plug wrenches exist but maybe you can find an open ended spanner to fit ..... alternatively, and probably the best solution, you should be able to buy a socket to fit
 
Last edited:
Impeller fine and strainer clean.

Decent amount of water coming out the exhaust.

The heat exchanger could do with an acid bath, but next weekend is the delivery trip and I’m back in work on Tuesday.

I need to do the best I possibly can tomorrow
 
My wife thought of this when I had tried every combination of tool that I had on board plus loss of copious amounts of blood.

The square end of a socket is exactly the same size as the drain plug.

Taking that further, find a socket that is the same size as a short extension bar (I have a vague recollection of 12mm), put the socket square on the plug, push the bar into the socket, connect to the handle and you’re there.

I found it useful to wind some electrical tape to hold the socket to the bar.

Quick edit, in effect just reverse a socket.
 
steveej said:
Impeller fine and strainer clean.

Decent amount of water coming out the exhaust.

The heat exchanger could do with an acid bath, but next weekend is the delivery trip and I’m back in work on Tuesday.

I need to do the best I possibly can tomorrow
Click to expand...

While its drained take the HE to coolant pump hose off the HE outlet connection on the bottom and check that outlet is clear... Others have had trouble due to that becoming blocked.

#11

16615.jpg
 
Last edited:
Another way is to use the socket the wrong way (as suggested) and use a large Allen key. Then replace the square headed plug with a brass tap. Early versions of the 2020 had a tap as standard. If you look at the exploded view of 2030'a' it shows the tap and Volvo part number.
 
Well yesterday was fun once I had negotiated the day off work with my boss.

Took the rubber boots off and removed the heat exchanger matrix. Sea water side was fine but fresh water side absolutely covered in grey/brown gunk. Cleaned up very nicely after an hour in the sonic bath for which there was no yard fee! Whoop whoop.

a 6 inch extension bar from a 3/8 inch socket set reversed allowed me to get an adjustable spanner on the other end to remove the drain plug. I am absolutely convinced this had never been removed as the paint was completely unblemished. I will be purchasing the tap as this will be much easier in the future. They must have been topping up with coolant so after 15 years it was probably 90% coolant mix.

I did buy some special acid for the first flush, run up the engine for 5 mins then let it work its magic for about 40 mins. You could here it hissing and bubbling away and some drips from the self bleed pipe. Should have left it longer as I got properly sprayed when I removed the drain plug. Lots of muck came out. Two fresh water flushes later running up the engine for 3 minutes a time and even more muck came out.

My only concern now is the possibility of the thermostat being clogged but it is a bugger to get to and I don't have the gaskets to replace the heat exchanger tank. I am bringing the boat home this weekend from where I bought it at the start of the year so I have run out of time.

The heat exchanger is a lot cooler but the calorifier pipe is still quite hot which makes me think the thermostat is not working as running up to 1800 revs whilst tied up the oil alarm went off and coolant was leaking. So I am not totally happy but it is better than it was.
 
Last edited:
Our 2020 has a tap (a pair of ears which you can not reach to turn unless you have the foresight to do it when changing the oil filter) there is a flexible tube permanently connected so you can collect rather than discharge in to the engine tray. Access to the starboard side of the engine where the oil filter, oil drain pipe and coolant tap is rubbish because the loo compartment is tight to that side, the Finngulf we had a while back was similar but they had provided a decent size insulated hatch which allowed you to change the oil from the head. I plan to make a wooden handle device to solidly grip the tap lugs which hopefully might allow me to turn it on or off while keeping some skin on my knuckles but hope I will not need it until the end of season oil change.
 
Well, week last Saturday I motored from the berth on the start of the delivery trip. 10 mins later and about 2 litres of coolant in the engine bay! Took heat exchanger cap off and it was still full! It only takes 2.3 litres.

Rubber end cap at the back of the heat exchanger not connected properly and sea water was getting in. Now fixed but there is a leak where the end cap connects to exhaust elbow which I hope to fix this weekend with some new end caps.
 
Be careful with the salt water in with the fresh., mine did this and eventually the thermostat failed shut causing the engine to overheat and seize. Horribly expensive to fix.
 
wiggy said:
Be careful with the salt water in with the fresh., mine did this and eventually the thermostat failed shut causing the engine to overheat and seize. Horribly expensive to fix.
Click to expand...

Now it's home, there will be full on flushes this weekend. Probably going to take the elbow off and have a proper look inside and sort out the corrosion at the heat exchanger nipple. Thinking of giving it all a wipe down with a wet tea towel as well just to get rid of any salt residues.
 
Ok, so boat now home after nursing the engine back from plymouth to cardiff.

Thought I had sorted the problem before leaving but on delivery lots of leaking water from rear heat exchanger end cap where it connects to elbow. So kept to no more than 2000 revs otherwise is was spraying all over the relay box.

When I first got back the bilge compartments were full of water. I think it is the calorifier with water getting to hot and being vented to the bilge and then filling up again and repeat....

went down last weekend and flushed it all a few times as I wanted to do a proper job after the seawater mixing fiasco. Put it all back together and run the engine up in neutral. Noticed the pipe connection from antisyphon valve to heat exchanger inflow end cap had started to separate at the end cap. Touched it with my finger and boom, fountains of water!!!!!!! closed the seacock, climbed up into cockpit and stopped engine. Think my heart missed a beat.

Drained all coolant down again, and took off the end caps....... found water sat in the elbow nipple.

Elbow must be blocked, not helped by 25 hours at 1900/2000 revs on the delivery which probably made it worse with extra coking up of an already heavily coked up elbow.

Back pressure from the exhaust being at least partially blocked may be responsible for the leaking rear end cap on passage and also the hose parting with the forward end cap last weekend?

Am I on the right lines with my thinking?

Having terrible trouble getting the elbow off. Have managed to free the top two nuts but bottom two very difficult. Being covered in green paint obviously doesnt help.

Any tips for getting these last two nuts off? Do I need to strip the paint off first? if so, how?

Is there a danger of crusty bits going down the exhaust hose from the elbow and getting lodged in the water trap (which was only replaced a few months ago?

Help!
 
I had to remove our blown elbow recently on our 2010 . I used the admirables creme brule gas blow torch with a very concentrated flame to burn off the paint. Be very very careful not to snap the studs as extracting them is a much bigger job. If you have been lucky then your nuts will not have rusted to the studs. Mine were and needed a couple of days of patience repeatedly using the torch and applying Plus Gas to help break down the rust locked threads.
I was only able to use a very small socket and T Bar. The standard nuts are 12mm AF flange nuts on an M8 thread. They are very easy to round off so don't be tempted to use a combination spanner to undo them.
I have replaced ours with standard M8 Stainless flange nuts which are 13mm AF . This gives a much bigger drive area for unfastening which should make my new service schedule for checking and cleaning the elbow easier in the future.
This may only be possible with a stainless replacement fabricated elbow as there is much more clearance than with a cast elbow.
 
You must log in or register to reply here.

Share this page

Top