Volvo AQD21 overheating problem

[jamesm]

Hi.

I'm after some advice about an overheating problem.

I recently had a rush of blood to the head (against my wife's better judgement) and bought a Princess 32 with twin Volvo Penta AQD21 diesels with Volvo 270 outdrives. The starboard engine has always ran a little warmer than the port engine, but not overly so. However, the other day, the temperature gauge rose until the needle just about hit the red. I ran the engine at idle and the temperature dropped to normal. After replacing the raw water pump impeller, the problem appeared to be resolved and I was able to pacify my wife with my ability to maintain old engines, restoring her faith in my rash purchase.

However, after about an hours cruising the next morning, the temperature on the same engine crept back up in to the red. I used my last remaining spare impeller, but it made absolutely no difference, the temperature increased and rose almost to the red even with the engine idling with no load.

Can anyone suggest a solution, please?

By the way: the boat has only been used on inland waterways for many years, the previous owner had the heat exchangers re-conditioned two years ago and the boat has seen little use since then.

Thank you.

 

[Divemaster1]

Any pieces out of the old impellor ?? ... if so you could have pieces blocking the cooling system ??

Cylinder head on these is known to warp, so;

1) have you till got coolant in the header tank ??
2) how does the oil filler lid look like when you remove it ... or oil look like ... milky?

If you have coolant and no issue with oil, then I'd suspect cooling water circulation pump ..... or another favourite of mine ... blocked exhaust bend (less likely if only run in fresh water).

 

[jamesm]

Thanks for your reply, Divemaster1.

The old impeller was intact, but the vanes were a little soft. No residue or missing pieces.

There is still coolant and the oil still looks like oil - no emulsification.

Not something I'd readily admit too, but, to my ultimate shame and embarrassment, I did run aground on a mud bank, stalling the engine in the process. This was after I'd replaced the impeller the first time and the engine ran OK for the rest of the day (about 3hrs cruising).

Sorry, if all this is a bit of a basic query, but I'm new to outdrives...

 

[macnorton]

Do you have weed strainers on the inlet and is there a good flow of water through it, if you do not have weed traps I would disconnect the pipe that feeds the raw water into exhaust and check with a bucket you have good flow of sea (River) water.
If that is ok these engines do have a habit of the head gasket corroding, a friend had the same problems with his and I replaced the gaskets and got the head faces machined which sorted it.

 

[Divemaster1]

....
Not something I'd readily admit too, but, to my ultimate shame and embarrassment, I did run aground on a mud bank, stalling the engine in the process. This was after I'd replaced the impeller the first time and the engine ran OK for the rest of the day (about 3hrs cruising).

Sorry, if all this is a bit of a basic query, but I'm new to outdrives...

Your outdrives will have it's water intake at the lower front part of the drive .... (small grille I suspect without being fully clued up on the Volvo 270 drive). This grille (and pipe) could have been clogged up with mud etc., when grounding and pending on where / how much debris have found its way into the cooling system and caused a blockage ...you may have to trace this and the first proposal from macnorton is a good place start to see if you have water circulation... if not you need to start looking for blockages ...

 

[jamesm]

Thanks very much for your replies, guys. I'll get to it at the weekend...

 

[scottie]

Your outdrives will have it's water intake at the lower front part of the drive .... (small grille I suspect without being fully clued up on the Volvo 270 drive). This grille (and pipe) could have been clogged up with mud etc., when grounding and pending on where / how much debris have found its way into the cooling system and caused a blockage ...you may have to trace this and the first proposal from macnorton is a good place start to see if you have water circulation... if not you need to start looking for blockages ...

Look for 1" hole under the nose of the leg and rod through grid is secondary

 

[Dave_Seager]

I have had a Princess 32 with AQD32A engines and, as far as I know, the AQD21A engines are almost identical but have two less cylinders.

Raw water strainers were not usually fitted although I fitted them to mine eventually. The first thing that the cooling water reaches after the intakes in the leg is the oil cooler which is fitted by the oil filter, high up in the pipework leading to the raw water pump. This is easily blocked by weed and other small debris.

The cooler consists of a stack of small tubes. The water flows through the tubes while the oil flows between them. The whole assembly is held together by a single bolt through the centre. Once this is removed the two end castings can be removed and the tube stack slid out. There is a large o-ring in each end which seals everything. Ideally these should be replaced but they can usually be reused a few times. Be prepared for a small spill of oil when you open it up but most of the oil will probably drain back inside.

 

[jamesm]

Thanks for all the replies.

Problem solved: the oil cooler was clogged with weed.

Will now fit some raw water strainers....