wax build up in Volvo Penta heat exchanger

[surfschnoz]

Hi I wonder whether anyone can help me
I have a 2001 Volvo Penta 30 HP diesel auxilary in my sailboat.
At the begining of the season I can chat along at even 3k revs at full hull speed if I like no probems - "sweet as a nut". e.g. I used te engie at 2700 revs for 22 hrs non stop in July.
towards the end of the season my max revs before overheating gradually gets down to 2600. - literally as soon as I raise the revs it overheats withing a few minutes
Fortunately all I have to do it tunr my hot tap on and my calorifier brings the engine temp down within a minute.
I check the water intake & clear it regularly ( no difference)
water gushes out no problem
I replace my impeller annually
I am using high quality 5 yr antifreeze that I chage every year
Each season I get the engine serviced and there is a substantal ammount of waxing in the heat exchanger that needs taking out & presure hozing off.
lst year I gave it a double flush through with inhibitor - I think it improved things but she over heated again last weekend.

Why does the wax build up?

is it beacaue the engine is running hot ( a symptom that makes the problem worse ) or is the wax likely to be the complete cause of the problem

any ideas on how I can stop the wax build up woud be much appreciated!

thank you! Richard

 

[Scott Danforth]

is this "wax" buildup on the raw water side or the glycol side of the heat exchanger? if it is on the raw water side, it is simply contamination and crud that is in the water that is being deposited. if it is on the glycol side, it could be the wrong antifreeze that is having the salts precipitate out.

 

[jerryjerry05]

Pics?

 

[surfschnoz]

Wow Thanks for the vvv quick responses Jerry & scott - v much appreciated!!!

It is on the "fresh side" and this year I used different 5 yr antifreeze with no change ( Einstein's definition of insanity applied " repeating the same thing expecting different results") this came recomended by my engineer. who serviced the engine & flushed the system.
any recomendations?
could the wax be a symptom of a slow leak between salt & fresh side? ( she v raraely if ever needs topping up with coolant and even when she does I may get 1/2 of a pint in a season )
I have had the probelm of the cylendar creeping up inside the heat exchanger before this could be related?

what is the effect of over ehating on the coolant?

when she "over heats" it is not at all dramatic - does not look obviously hot no steam and the engine still looks like new.

sorry I dont have any pics but when it is cleaned out again I'l take some

thanks again

Richard

 

[Scott Danforth]

which 5-year anti-freeze are you using? Dexcool (OAT), G-05 (HOAT), or G-11, G12, G13? due to the specific corrosion inhibitors used, they do not mix well with others and will precipitate out to a sludge if there is a trace of the green anti-freeze. Use only the Antifreeze that was originally supplied with the motor.

another issue may be your oil cooler or head gasket could have a minute leak. this would be identified by a simple coolant test looking for petroleum by-products. this would indeed coat the inside of your heat exchanger as well as the other coolant passages within the motor with a film.

 

[surfschnoz]

Scott thank you both really good points

I'll check the coolant at the weekend ( bottle is on the boat)

this year I certainly did not mix with other coolants ( as I was being extra careful) but I MAY have last year.

re head gasket - I see your logic but would not expect wax from that would I?

thank you

cheers

Richard

 

[Scott Danforth]

here is something that I found http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1682519

Wood Bleach and Washing Soda. Coin of the realm. Search for 99-06-02-012D, it's a GM service procedure for fixing the sludgy/coagulated coolant problem. The flush they call for is no longer widely available, but powdered wood bleach (available at some Ace hardware stores, and probably other places) and washing soda (I found Arm & Hammer brand at an IGA store) are the ingredients they call for. Some people prefer citric acid (from the bulk/health food store at 1 pound per gallon-apparently a Mercedes-Benz recommended procedure), but I think oxalic acid (wood bleach) is particularly good for the coolant-mix problem.

Doesn't hurt to hit it once with dishwasher soap (not dish washing soap, you understand, but non-sudsy soap that goes in the dishwasher) first to take out any oils and let the acid flush work. Flush well between soap and acid. It's a long, messy procedure, but it does the trick. The real key is getting it hot enough during the flush, and rinsing completely, with engine running, between flushes. Getting a good rinse is almost impossible without hooking it up to a hose (hot water is definitely better), so the Flush 'n' Fill kit really helps.

I think you're better off driving it around than doing the high-idle procedure in the bulletin, but it's up to you. FWIW, mine kept belching horrible crud for 3 iterations of this procedure, but it had mineral scale worse than I'd ever seen. All better now.

Once it's totally cleaned out, you can pick a coolant without worrying about interactions. Don't be shocked if it starts leaking after you do a thorough flush. I'm not saying it will, just that sometimes the flush dissolves some crud that was plugging up a little leak. I found a couple of o-rings leaking after the procedure.

Also, be careful with the acid solution, it will mess with the finish on metal and plastics. I wouldn't let it dry on any parts you care about the looks of.