Volvo penta aqad40b overheating??

[Boatymcboatface123]

Hi all,

I'm looking for some experienced advice or tips.

I have just recently taken on a job diagnosing an old AQAD40B that is overheating.

The owners bought the boat last year, It started overheating couple of months after.

The engine has no hour meter or maintenance history.

They had a mechanic who:

1: replaced thermostats
2: clean heat exchanger
3: replace end caps (heat exchanger)

Now I took over (unfortunately) and I have checked:

4: exhaust mixer elbow, removed it wasn't blocked, ran water through to check
5: sea strainer
6: G/B cooler
7: raw water pump and impeller
8: replaced drive belts (jcw pump pulley slipping)
9: ran the engine with raw water discharge hose removed to assess flow, seemed quite sufficient, flow increased with rpm.

I used a temp gun on sea trial, all temps on raw water circuit 25-30'c, jacket water gets up to operating temp and keeps climbing to 90'c+

I haven't checked the oil cooler or aftercooler yet as there is more work involved and the raw water temp and flow seemed satisfactory??

The jcw pump pulley spun quite freely when belts removed, didn't look like it was leaking from teltale, but how would I know if jcw pump is causing it to overheat?

Any advice or tips would be much appreciated.

Cheers!

 

[Tassie 1]

G'day,
same motor,
same problem,
( seems to be a fairly common problem looking at different forums )

Do you know how the H/E was cleaned?
what was found inside?
you're going to have to pull the oil cooler as well...as much as it's a major pita getting it out and back in,

a good acid bath may be needed for both,

was the elbow in good nick or corroded?

we have tried a number of different things on " ours " and it still overheats,
new tstats, impellar, cap, belt, elbow etc etc blah blah,

Extremely frustrating...
owner is almost at the stage of replacing it with a petrol motor...almost

interested in seeing any answers to your question ourselves,

cheers

 

[Scott Danforth]

start with a new impeller for the sea water pump AFTER you back flush the whole cooling system and get the shell or stone or dead fish out of where ever it is. 99% of the time, there is a foreign object blocking flow.

make sure the HX is clean

 

[alldodge]

Place a piece of clear hose right after the pump to look for bubbles. Can also install same in other locations

 

[Tassie 1]

'We dun ' that too.

 

[QBhoy]

Hi

statimg the obvious perhaps but make sure the seal is good on the SW strainer. Any break in this seal and it will not pump water.

Other common thing with similar set up is if it has a t off to heat the domestic hot water...the pipe work can leak or educt from the system. Perhaps not in your case though.

Be checking the impeller first off..but make sure that sw strainer has a good seal. Honestly...if the lid is off or not sealing, you won’t get water through it.

 

[Lawnpro979]

Check this..... make sure the hoses are on the right outlet....this was my problem after wintering