Volvo AQD40b Thoughts please

[Medway Mudlark]

A little under a year ago I purchased a Fjord 815, cos SWMBO said it was the right one! After having it on hard for 6 months rebuilding/replacing from the keel up it was deposited back in the water again, and until recently has only toddled around on the Upper Mudway. A couple of Sundays age we decided to give it a shock and take her to the salty stuff for 2 reasons 1. cos it was a nice day out, and second was to see what the engine/hull would do at higher engine revs than 1200. Most of the day was spent at around 1800 rpm apart off Grain where we took her to wide open, then throttling back to 3000 rpm. On checking the engine bay on the slower return trip I was greeted with a fair amount of water under the engine which had come from the filler cap on the heat exchanger, and the level was at the top of this. Prior to this the boat had spent the last 15 or so years up the Thames, The engine maintained its temp of just under 90 deg on the fast run and did not overheat. I am half tempted to run some rydlyme through the freshwater system, but something in my head says could this be the aftercooler matrix. Engine is an AQAD40b (165hp) on 280 SP leg. Am asking on here as there seems to be little mention of this particular engine and welcome your thoughts please

Regards.View attachment 54201

 

[Jegs]

Hopefully one of the experts will be along shortly but, in the meantime, here's my penny's worth. If the fluid, which should have contained antifreeze not merely water, was coming out of the filler of the header tank & not the overflow, the cap probably needs to be replaced, although it may not have been correctly tightened.

Further, if the engine did not overheat then it is possible that there is a leak between the two coolant systems: I trust not!

Good Luck

John G [TMD41B]

 

[superheat6k]

Outdrive version of the TMD40B. IMHO good engines, and these went on the form the basis of the TAMD (after cooled) series then the KADs and KAMs.

If you are forcing water out of the fresh water system I would bet the seawater / freshwater cooler has perforated. The seawater is pumped at higher pressure so forces into the freshwater side of the engine then out of the cap into the bilge. Short term it won't damage the freshwater system, but make sure you flush thoroughly once the problem is dealt with.

I had to replace one on my last boat VP quoted £1600, I got on through Keypart for ~ £900 on a deal for buying two.

Probably not what you want to hear.

The heat exchanger is a square plate heat exchanger, housed behind / inside a square cover at the belt end of the engine. They come out via the cover complete with the seawater stub pipes connecting the opposite end, but the O rings are normally very tight and difficult to get free - Do not pound the matrix inside the seawater tubes. Gently push against the seawater tubes and rattle the matrix from the access end until it comes free.

Liberal amounts of WD40 around the outside of the seawater tubes might help loosen the O rings holding the matrix in place.

The seawater side should pass a pressure test to say 1 Bar. A simple test is to place a balloon over one pipe and pump up the other somehow, e.g. a col with a hole and tube in. If the balloon inflates and stays inflated then the HE is OK. If you immerse the freshwater side in a bucket as you pressurise a leak will be obvious.

I have a workshop manual for the TMD / TAMD - PM me if you would like a copy, for which I will suggest a donation to the RNLI.

 

[Medway Mudlark]

Sorry, Thread title may have gone a bit 'wibble'. Engine is AQAD40b 165 bhp turbocharged and aftercooled, also has 2 water intakes, one through the leg and t'other by way of seacock and strainer which are joined together to feed the seawater pump. Hence my comments on opening thread about the aftercooler.

 

[dragoon]

If the engines are 'b's then you have tubed heat exchangers, rather than plate exchangers which were on the 'a's. In this case the separation of fresh and raw water is not only the tubes, but also a rubber cap on the rear end of the heat exchanger. If this is not properly fitted and secured with a giant jubilee clip, then the water passes from the sea water side to the fresh water, pressurises the system and dumps it in the bilge - don't ask how I know!

I doubt as your problem is a blockage - usual blockages when they occur are oil cooler (1st cooler after the water pump and far too small by design IMO) and the exhaust bend.

Check the end cap first. You may be able to see if the cap is fitted tightly without removing it - there are 2 bands/jubilee clips at the rear - they should both be tight. The smaller of the, separates the 2 water systems.

 

[oldgit]

Before you go dismantling the engine.........
Am going to presume that like most of us,you assume that the cooling water in the header tank should be brimmed to just below the filler cap.
The more full the better etct. etc....
This is probably fine all the time you are widdling about at around tickover up on the freshwater bit..
However ! When in the real world of tides (and in your case towing something) and making that engine work for living by getting it hot and bothered things change.
My AQD 40A engines simply dumped anything over a small amount of water remaining in the header tank from cold into the bilge without fail.
My Perkins M135 behave exactly the same.
Pretty certain lots of similar comments about other engines with same penchant.
Worth a try before spending time and money and will cost no more than a trip through the lock.
Provided a small quantity is visible in bottom of header tank would go out again and see if you lose any more....
If problem solved fine ,if not on to plan B and get your wallet out..

 

[Medway Mudlark]

Thanks OG, already have drained header tank to a level just on the thermostat plate, as per VP manual, but seem to end up with more water than I started with! Trip to bottom end a couple of weeks ago was to 1, see if the overheat problem was resolved - it appears OK now, 2, to see if the trim pump worked now I've repaired it - it does! and to see what other gremlins awaited us after loading the engine, it was also a bonus to have a nice day out down to Queenboro' and back. Looks like I'll have to check the connecting hose between heat exchange and aftercooler, and if that's OK remove both and dismantle and physically check both, but i've got the next few months to do it and the interior refit can go on hold for now.

 

[oldgit]

My earlier version of your engine had the square box heat exchanger with a rather fragile heater matrix inside.Over the years the matrix had flexed and a number of seams had cracked.Did use it for a bit before biting the bullet and pulled the thing to bits(it is suprisingly agricutural and simple.) and soldered several fractured seams and tubes.Despite losing perhaps 10% of the cooling area due to repairs it functioned perfectly OK for many years.
Main problem is getting all the O rings and seals to stay in place as you reassemble.
A kit is available,but like me you may end up not using much of it.
Ps. Remember to replace the little pencil anode in base of casing,mine had long disappeared,


Exibit 1 Yer honour.