Exhaust Elbow Removal - Stuck Nuts (Volvo MD2020D)

[SV Kittiwake]

I'm not sure if it's exactly the same but I replaced the elbow on our MD2040D. I could get a 1/4inch ratchet with extension arm on (mine is bahco). The nuts are absolutely bar tight though, I had to slip a stainless tube over the handle of the ratchet to get it to budge and even then I was at full strength, even bent the handle of the tool. I think a 1/2 to 1/4 with extension bar would have been worth trying on mine if I'd had one, but not sure if it fits on the smaller engines. Vyv C is usually right about these things - follow his advice if you can.

 

[steveej]

Well i'll be back down on Saturday and have tooled myself up with....

some 2mm drill bits
a nut splitting chisel
'crack it' freeze spray
a creme brullee burner
a nut splitter (but dont think it will fit)

and failing all that I'm going to take the entire heat exchanger unit off with the elbow attached and take it off the boat. Ball ache but will at least allow me to change the thermostat at the same time.

 

[steveej]

stupid question, but I believe the elbow has a top chamber (for the sea water coming off the heat exchanger) and a bottom chamber (for the exhaust gas) and then the two chambers open out and connect with each other lower down the elbow. Is this correct?



As you can see exhaust salt water from the HE is sat at the nipple and not draining away.

If there are no chambers and it is just an open unit then I could probably drill it out and wait until the end of the season for a proper fix.

 

[peteK]

stupid question, but I believe the elbow has a top chamber (for the sea water coming off the heat exchanger) and a bottom chamber (for the exhaust gas) and then the two chambers open out and connect with each other lower down the elbow. Is this correct?

View attachment 79288

As you can see exhaust salt water from the HE is sat at the nipple and not draining away.

If there are no chambers and it is just an open unit then I could probably drill it out and wait until the end of the season for a proper fix.

There is an inside tube which the exhaust gasses exit the engine with the water cooling surrounding this,if you poke a screwdriver in to the spigot and clean it out you will hit the inner tube there is about 3/8 inches between the outer and inner casting.As I said in post 13 this often blocks and causes overheating.

 

[steveej]

There is an inside tube which the exhaust gasses exit the engine with the water cooling surrounding this,if you poke a screwdriver in to the spigot and clean it out you will hit the inner tube there is about 3/8 inches between the outer and inner casting.As I said in post 13 this often blocks and causes overheating.

ok this makes sense and it looks to me once it had dried out the following week that it's blocked downstream of the spigot/nipple as i filled the nipple up with water again and it just sat there.

 

[peteK]

If you take off the rubber exhaust hose and look back up the exhaust outlet, a mirror may help, you may see where the problem
is.

 

[Stemar]

One of these https://www.toolstation.com/monument-soldering-brazing-pad/p31037 might help to protect nearby wiring

 

[TSB240]

Well i'll be back down on Saturday and have tooled myself up with....

some 2mm drill bits
a nut splitting chisel
'crack it' freeze spray
a creme brullee burner
a nut splitter (but dont think it will fit)

and failing all that I'm going to take the entire heat exchanger unit off with the elbow attached and take it off the boat. Ball ache but will at least allow me to change the thermostat at the same time.

I was the guy who nicked my admirables creme brulee torch to do this recently!

I have just had a thought. I did mine without draining all the coolant in the engine. The exhaust manifold would have been full of water. This would explain why the torch took ages to get any heat into the nuts as I was probably heating a litre of water and the engine block was also acting as a big heat sink. DOH.

Any wiring is easy to move to avoid melting or catching fire . Just disconnect the multiplug and remove the starter/glowplug relay black box before starting.


I had to heat cycle a number of times before the bottom two rusted nuts broke their seal. I could not get them cherry red which would have been ideal!

If in doubt or not enough time just take the manifold and exhaust bend off complete and take it home! You might also check for a partial or nearly complete blockage in the hose nipple at the bottom of the exhaust manifold especially if the antifreeze was not changed every two years.

The bolts on the manifold are long and twist a hell of a lot if the threads are at all corroded. Use copper grease when you replace all of your bolts and nuts and you wont have a problem when you want to check your elbow or manifold every two years...

 

[TSB240]

stupid question, but I believe the elbow has a top chamber (for the sea water coming off the heat exchanger) and a bottom chamber (for the exhaust gas) and then the two chambers open out and connect with each other lower down the elbow. Is this correct?

View attachment 79288

As you can see exhaust salt water from the HE is sat at the nipple and not draining away.

If there are no chambers and it is just an open unit then I could probably drill it out and wait until the end of the season for a proper fix.

Trust me if that is so badly blocked I bet that the calcium and exhaust deposits have actually backed right up inside your exhaust manifold upstream of the elbow. I was still getting water through mine and I was amazed that the engine could keep running with only about a 10mm dia cross section of uncoked exhaust elbow.