AQ140 exhaust manifold

I

IanC

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Has anyone ever changed the water-jacket that cools the exhaust manifold on a VP AQ140 - it has been suggested to me (by Keyparts) that these need to be changed after a few years as the rear section of them rusts badly and is a common reason why overheating occurs on these engines.

I have been experiencing a funny problem - the engine looses it's water (fresh water) and overheats only after about 1.5hours of cruising. I have renewed the impeller, checked there are no blockages, rodded the oil cooler - done all the usual things - and can't seem to get to the bottom of it - so - I am now wondering about this water jacket thingy - and though I would ask for some thoughts from you knowledgeable gentlemen before I embark on trying to take it off and let My Keyparts sell me one for £250!

I would really appreciate any thoughts on the matter.

Thanks

IanC
 
Are we taking about the actual ex manifold or the riser at the rear of the engine.
The riser can be removed and with care(involving lots of brute force and hammers }most of the internal scale removed.Normally blocked riser show up when going at full speed when temps rise but go back down again at slow speeds.In severe cases of blockage hoses will actually burst under the pressure.
This article is worth a read if you have 5 mins sometimeRusty Risers
 
I think I am talking about the big black water jacket that runs the length of the engine from front to back which then attaches to the pipe that goes out to the outdrive via a rubber hose. I don't know much about the 'riser' - I have now looked at your link - thanks.

IanC
 
Hi Ian
First of all there is no riser on the AQ140, the exhaust manifold is one piece. The exhaust part is surrounded by the water jacket, so you have hot exhaust gases being cooled by salt water in a cast iron manifold, (does the word corrosion come to mind) the two then mix at the downward facing elbow that joins the rubber sleeve ajoining the pipe on the transom shield. The main problem is the downward part of the manifold, it corrodes thereby blocking the water passage, it gets worse what can happen is the inside part (exhaust) corrodes through spraying hot salt water into number 4 pot, corroding the aluminium cylinder head,VP have a tool for cutting the corrision out and fitting a stainless ring in its place, it can usually be done in situ. Although it sound doom and gloom its not that bad. I had a pair of AQ140's for 18 years and after replacing the first pair of manifolds every winter lay up I would remove the manifolds, flush thru with a hose, it always amazed me the amount of crap that came out! and then left them to soak in a oil bath ready for the next season. I hope this is of some help.

Steve
 
Hi, assuming an aq140a is the same as an aq 140 I have removed and replaced one of these items when the water kept blowing out of the weed trap filler cap. Keypart ( who I normally regard as very good and I daresay were trying to help ) suggested that the likley cause of this was a blown exhaust manifold causing pressure in the raw water circuit. I removed the manifold and on my workbench filled the sea water side with water. After two days not a drop had gone and the exhaust side was dry as a bone. There was very little corrosion in there as well and my engines are pretty old ( and now for sale if anyone wants a pair with complete drives!! ) . My fault was a blocked oil cooler.Taking them it off was just a matter of several long bolts, and disconnecting the various water connections. I would suggest removing it and doing the same water holding test before forking out for new. When replacing get new exhaust gaskets and buy car ones cause the'll be a lot cheaper. The engine is a volvo B21 which was used in cars like the old Volvo 245 so parts are available from motor factors. They are heavy and when replacing be careful not to trap the big rubber doughnut or you can puncture it as I did!! Hope this helps please feel free to ask or PM for further details... cheers Iain
 
Totally agree with your reply,especially regarding buying the gaskets from motor factors, I have cross numbers for almost all the replaceable items, otherwise from Keypart.
However regarding the original problem from IanC in which he states that he 'has rodded the oil cooler' (sounds painful!!)I assumed that it was clear therefore the problem must be the next item in line which is of course the manifold and is a usual suspect, from there is it only the down pipe and out through the outdrive.
That is the reason for the reply that I gave.

Steve
 
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