VOLVO MD 2020 - OVERHEATING

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nunners

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Hi All,

I'm a newby so here it goes...

Ive got the Volvo MD2020 (with prop shaft) that overheats. Raw water intake works, no blockages. Fresh water cooled with expansion tank. Drained most of green coolant out through exchanger cap & Opened front of heat exchanger. (couldn't open bottom fresh water plug without right tool, but drained completely 12 mths ago).
Revealed a tiny bit of sea weed and two of the heat exchange pipes blocked. Stuck needle into pipes to clear those blocked - Cleaned up, checked for scaling (looks good) and put back together. Maybe should have opened other side of exchanger and pushed through a steel stick to clean completely & possibly flush??
Still overheats after 1 hours running at 3/4 rpm. Prop clean & raw water intake clear.

1) How do you remove the inner heat exchanger tubes and give an acid bath without removing the heat exchanger???

2)Does the cap on the end of all those h/exchanger pipes come off for cleaning?? easy to put back?

Pumping plenty of water & possibly steam too. Noticed water in bilge after running for an hour. Checked pipes r/w intake and all look good. Stern gland ok.

Thanks for any advice. . .

Cheers, /forums/images/graemlins/confused.gif
J.
 
1. Check Thermostat - to remove undo raw water hose from sea water pump, loosen alternator and press against block, remove screws that hold the alternator bracket and electrical distribution box in place; these also hold heat exchanger to engine so remove this and thermstat and a large spring that holds it in place can be removed and checked.

2. Tube stack is removed by removing the rubber hoursings away from either end of the exchanger and then pushing out th tubular insert. On reinstalling, insure large holes point downwards and small air bleed hole is upwards. Should be marked on body. POush in until it protrudes equally at either end.
 
Had an ongoing problem last year trying to pin down overheating alarm on my port KAD32. Eventually tracked down to be the sender unit which is worth checking if you can get to it before doing a lot of other work. Apparently Volvo senders do often go wrong. One useful thing I bought was an infra red thermometer to beam round the engine to see what temperature actually was at thermostat housing etc. Less than £20 from maplins
 
Thanks for the quick response! I removed the tubular insert & cleaned in acid with toothbrush etc & looking forward to re-installing. It was quite easy to remove.
Probably obvioous, but where is the small air bleed hole located? It looks like the brass tubes for cooling are all the same size/diameter.
After re-installing how do you bleed the cooling system of air? I wanted to just refill from the top of the exchanger, run and check levels when warmed.
 
As I recall my 2030 on installation, we just filled up the header tank and that was that. There is no procedure described in the manual which suggests that bleeding is not an issue. Any air in the header tank should displace itself through the pressure cap as the system gets pressurised. As to the raw water side, I doubt that needs bleeding - certainly didn't on installation. I just filled the header tabk, connected the raw water and that was that. The drawing does not show the small air bleed hole but the word 'UP' is very prominent
 
Ok, all very clean - put back together and running perfectly to start with...after about 40 mins of hard running she seems to be very hot (no alarm bells this time). Feel like I should have got out that thermostat!

"to remove undo raw water hose from sea water pump, loosen alternator and press against block, remove screws that hold the alternator bracket and electrical distribution box in place; these also hold heat exchanger to engine so remove this and thermstat and a large spring that holds it in place can be removed and checked."

There is one large nut on the side about 22 in size... what's underneath it when removed? Or is it very definately only accessible by removing the h/e as described.

Cheers,J.
 
Yes ive seen now in the online manual, ive gotta open and remove the heat exchanger to get to the thermostat...2040 has a neat external plate...a lot easier for the backyard mechanic /forums/images/graemlins/smile.gif
 
I think the 22mm nut is the header tank drain. Yeap I'd guess the thermostat is kn**ckered. You might need new gaskets for the heat exchanger/block joint
 
nunners said:
Stay tuned...I'll update when I've got into it!
Click to expand...

HI Nunners,

I was reading your thread about changing the thermostat back in 2009.You didnt come back and report on how you got on.
I need to remove my heatexhanger casing completely because previous owner ripped off the cap base! It needs to be braised, hopefull can source a new one or might just use a radiator top/cap. :(
How does the whole block of the heat exchanger come off? Any hazards? I have the workshop manual but it's not clear to me. Would appreciate yours/anybody's input before I tackle it.

Chris
 
Removal od tubestack, h/e box cleaning with HCL acid and replacing.

ChrisCalthrop said:
HI Nunners,

I was reading your thread about changing the thermostat back in 2009.You didnt come back and report on how you got on.
I need to remove my heatexhanger casing completely because previous owner ripped off the cap base! It needs to be braised, hopefull can source a new one or might just use a radiator top/cap. :(
How does the whole block of the heat exchanger come off? Any hazards? I have the workshop manual but it's not clear to me. Would appreciate yours/anybody's input before I tackle it.

Chris
Click to expand...

Hi. For the records and future readers.
So I have solved my Md2020d overheating problems. First: Previous owner ripped off the radiator cap filler neck.. being brass in Aluminium it was not poss to reweld. Not even an alu neck due to the Heatexchanger (h/e) box being marine grade alu. Previous repair was "drill three holes and screw down"! The system didnt hold pressure and would boil dry when worked hard (discovered battling 34knots to get home.) Due to lots of topping up with tap water calcification grew in the fresh water system.. blocking the pipes in the tube stack. This happened with previous owner... but the tibe stack was tuck in the H/e box. The centre collar of the tube stack was fused to the alu box. Hence it had not been removed but decalcifier had been put round the fresh water system with limted success.
After a near disaster overheating and near stopping the engine under the Kingsferry bridge I had to tackle the problem. Symptom: overheating if run over 1400rpm ona 30 degree day.. sea water flowing well but cool out the back. = no heat transfer... Engine was at 100degrees and cooking... (using infrared point and read temp sensor)
System drained.. I could not remove the tubestack. Should come out easily as described above. After much tapping it was moving but the pipes slid inside the centre support collar which was itself fused inside to the alu h/e box..
I removed the h/e box and elbow. How: remove Alternator and tie to the side. Remove the electric box and tie to the side. Loosen the bolts on the starter motor and remove the bolt nearest the engine to swing it down 5mm (unbelievable it prevents h/e box removal by a hairs breadth.) The h/e box slides off two rods that mount the electric box.
Once off I blocked the exits off except a top hole and filled the Alu h/e box with HCL Brick Cleaning acid at 10% concentration. It frothed away.... got warm.. take care with eyes and hands. This ate away all the calcification in three treatments over 1hour. Keep hose at hand running... Still the tubestack would not come out - I used a copper gas pipe hacked down the middle to slide up the pipes and nudge the collar/clean out calcification.. then a thin steel knife - tap tap and finally movement. More tapping and after 14 hours over two days ... The tube stack was out! The centre collar was now at one end so had to be gently worked back to centre.
More acid baths for both units. The tubestack was filled with calcification and the thermostat was clgged up with hard white fur too...
The unweldable filler neck - Back home, gently ground /sanded down to bare metal with craft tools and bonded the filler neck in situ with JB Weld, woven roving and carbon fibre strands make a solid bond.. it now holds pressure.
All cleaned up and reinstalled. A Tubestack is £750 and a new h/e box is £600. New thermostat, h/e box gasket and two graphite gaskets for the exhaust elbow was not too expensive. Silicate coolaHalfords at 50/50 with deionized water. Flushed the exhaust box and water pipes too.
Now runs at 2200 rpm and higher full power in gear ... engine temp stays at 75 ish which is when the thermostat opens.. the h/e box now gets up to 75 when pushed. Normally lower. Exhaust elbow gets hot again now and the water out the back is warm to hot.,. so heat exchange is working.
Phew.... back in action. Hope this helps anyone who has the same issue in the future - which is quite likely.
I also painted the flaked alu paint. with etch primer and green hammerite.

Points I researched in depth:
Coolant must be silicate. Not the orange stuff.
Only JBWeld is up to task. Other so called high temp epoxy metals all failed. Using glass fibre in the set is key - and good preparation.
Must use Etching Primer on the metal. Then enamel or hammerite. I in fact used grey spray Etching Primer from Halfords and dark green hammerite in a tin from halfords... after one coat of primer I mxied primer and hamerite on the engine itself to get the perfect colour. Apparently the TK paint from Volvo just peels off... Mine may too. We shall see.

Note: to change the thermostat on a Md2020d requires removal of h/e box, alternator, electric box and the starter motor (a little).... 15 nuts and bolts in all. (Yes a few swears at Volvo were uttered). Be sure to turn your electrics off. Have new gaskets at the ready with your thermostat. Also a gasket sealant like Samsonal or red hermatite. Plus to get at the 10mm bolts of the starter motor you will need 3 socket set extenders (or a long one and a short one all strapped up with insulating tape so they pull out in one piece..fun). Reinstalling be sure to tighten the jubilee clips on the tubestack (i used samsonal sealant one the tubestack ends,) to prevent sea water entering the fresh system - this was another cause of my calcification - which tends to happen when the tubestack gets blocked up....

Good luck.
 
Thanks for all that Chris, no doubt the evil day will come to my 2030 eventually as well!I do fresh out the raw water side annually after liftout, so hopefully I'm putting off the major job!
Very useful stuff, thanks to OP as well.
 
Cheers Paul,
One thing I would say is regularly pull that tube stack out at the minimum and use a kettle descaler or HCL brick acid to clean it up.... Another thing we did overnight was put kettle descaler in the top of the sea water intake and give the engine a quick turn to flush through to the impeller, tubestack and exhaust elbow as a "getmehome". White froth and particles of rust and all sorts came out the exhaust in the morning so it does something useful. I might be doing that once every year too.
Re the Coolant. The red OAT stuff eats yellow metals... i.e your tubestack. So stick to Silicate Coolant, green/blue. They must never be mixed or a gloop will form, so a good flush..
I also think a flush with descaler in the fresh water system is not a bad idea because it will free up the thermostat etc.But must be completely flushed out after with hose as these descalers do eat aluminium.....
Chris
 
ChrisCalthrop said:
Cheers Paul,
One thing I would say is regularly pull that tube stack out at the minimum and use a kettle descaler or HCL brick acid to clean it up.... Another thing we did overnight was put kettle descaler in the top of the sea water intake and give the engine a quick turn to flush through to the impeller, tubestack and exhaust elbow as a "getmehome". White froth and particles of rust and all sorts came out the exhaust in the morning so it does something useful. I might be doing that once every year too.
Re the Coolant. The red OAT stuff eats yellow metals... i.e your tubestack. So stick to Silicate Coolant, green/blue. They must never be mixed or a gloop will form, so a good flush..
I also think a flush with descaler in the fresh water system is not a bad idea because it will free up the thermostat etc.But must be completely flushed out after with hose as these descalers do eat aluminium.....
Chris
Click to expand...

Hi all,

Latest addition. The JB weld failed. In the end I replaced the filer neck with a solid alu "racing" neck with flange. Cleaned all surfaces and everything up and used Westpac 24hr epoxy with fibre filler to set it down. It is good to 65 degs and the H/E block should not exceed that. This had been solid for 18months now.
BUT
I have a new overheating problem again. ! There seems to be restricted flow in the fresh water side and water dumps out past the radiator cap through the overflow. Currently I am cleaning the tubestack in 8% Brickacid mix (HCL) and am going back to the boat today to try and flush Oxalic through the fresh side. Possibly might use HCl on the thermostat. The system has silicate dropout evident - which I was getting on the inside of the filler neck. but also found in the pipework of the tubestack - fresh side..
I am hoping the thermostat has not died - it is virtually new. Once again I am cursing Volvo design for the lack of access to the thermostat... also the lack of heatexchange capacity to cope with the sea.
Never will buy another Volvo. Idiots making the thermostat so inaccessible. Idiots.
 
ChrisCalthrop said:
Hi all,

Latest addition. The JB weld failed. In the end I replaced the filer neck with a solid alu "racing" neck with flange. Cleaned all surfaces and everything up and used Westpac 24hr epoxy with fibre filler to set it down. It is good to 65 degs and the H/E block should not exceed that. This had been solid for 18months now.
BUT
I have a new overheating problem again. ! There seems to be restricted flow in the fresh water side and water dumps out past the radiator cap through the overflow. Currently I am cleaning the tubestack in 8% Brickacid mix (HCL) and am going back to the boat today to try and flush Oxalic through the fresh side. Possibly might use HCl on the thermostat. The system has silicate dropout evident - which I was getting on the inside of the filler neck. but also found in the pipework of the tubestack - fresh side..
I am hoping the thermostat has not died - it is virtually new. Once again I am cursing Volvo design for the lack of access to the thermostat... also the lack of heatexchange capacity to cope with the sea.
Never will buy another Volvo. Idiots making the thermostat so inaccessible. Idiots.
Click to expand...
I have the same 2020(b) and suffered the same problem(water coming out of the radiator cap overflow pipe. My problem was the exhaust elbow was clogged, restricting the flow into the exhaust. Checking it is straight forward by undoing the 4 nuts holding it onto the h/e and removing it from the exhaust hose. WD40 or penetrating oil spray on the nuts is worth while too.
 
Hiya, that will be the sea water backing up past your jubilee clips into the fresh water header tank.... yep had that one... my exhaust elbow ("riser" in my case) was all coked up..

Well I just got back from working on it. With just the h/e pipe stack out I could get boiling water onto the thermostat with a funnel and get 8% HCl onto it.. bubbling away. for about an hour I did this.. sucking it out and adding boiling water + the HCL. Then I put it all back together and ran it for about 45 mins at full temp with the acid in the system. Then drained, flushed with 90degree water from the kettle about 8 times, each time running it up to 75 degs engine block temperature, about 58-66 degs H/e casing... on the third run I added sodium bicarb to neutralise. Finally the water came out clear, then I had one repeat of the issue when I poured virtually boiling water in and ran - it spat out a 1cm x 1cm x 2mm thick piece of gel/gunk, that was soft.. I put it on the side, when cold it was like rock.. so this must be the problem around the thermostat or in the pipework. Anyway after this I could run it at 2400rpm in gear and the temps stabilised about 78 for the engine block (near oil cap) and 70 for the h/e casing, so I eased back to 2000 and all settled back to 74 and 58 respectively..
I also tried a new rad cap and this certainly holds pressure better than the old one.
(Bear in mind I have a custom filler neck.
http://www.ebay.com/itm/Vibrant-Alu...-Filler-Neck-42mm-1-65-ID-20982-/121884581475)

Perhaps the underlying problem has been no pressure.

Anyway... happy to go out now... prob need to do a longer term descale in the fresh water system with Fenox...?
 
I have had the same problem and change my thermostat every year. Filler neck also has a split around the base so some of the advice here has been useful on repairing. I can add some advice on removal of the heat exchanger. You can carry out the process without having to remove the starter and sliding the housing over the two long studs. The studs that normally hold the electrical box can easily be removed by using two nuts backed off tightly on the stud thread. The studs can then simply be screwed out. The housing can then just be lifted out.
 
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