Grasping at straws a bit

[stuartwineberg]

If the turbo on my engine is overboosting due to poor wastegate adjustment - what symptoms would I see. I notice from the service manual that low pressure leads to smoke which I dont have. The manual gives dire warning of engine damage if the pressure is too high but are there signs? (apart of course from measuring the boost pressure)

 

[[2068]]

What engine? Most modern electronically controlled engines will drop into a reduced power limp-home mode with a warning light in the case of an overboost.

For a mechanical engine, you'd probably find out when the pistons or valves melted. I think you'd notice that. If you had an EGT gauge, it might read higher before the bang.

Actually measuring the boost is the way to go.

 

[volvopaul]

Still looking for your over heat problem stuart?

The answer will be from data read on a sea trial, your turbos have a mechanical wastgate that opens from boost pressure, to over heat if the valve was seized shut the paint would be burnt off the turbo, manifold paint would be discoloured and to achieve that you would be running near WOT to do this not at the revs you think its overheating at, also if boost pressure was so high the temp in the cylinder head and exhaust manifold would be so high you would see it from your heat sensing gun.

Have you had all the coolers off, also have you cleaned the CAC matrix on the air side to make sure its free from oil mist blockage.

 

[Racingfrank7]

Like above if your looking for over heating probs this is the wrong tree !
But as for over boosting, it would go better than it should, there would be a lack of black smoke or deposit on exhaust when run hard, and pos a glowing turbo ( no joke ) also as above if it's modern it will just go into limp. But the only exact way is to put a boost gauge in line and know the standard factory parimters ( putting in a boost gauge is easy & the gauges are quite cheap now )
If its over heating as above again ! And it's mainly under hard load I would check your cooler(s) arnt blocked or partially blocked.

 

[stuartwineberg]

As you say

Still looking for your over heat problem stuart?

The answer will be from data read on a sea trial, your turbos have a mechanical wastgate that opens from boost pressure, to over heat if the valve was seized shut the paint would be burnt off the turbo, manifold paint would be discoloured and to achieve that you would be running near WOT to do this not at the revs you think its overheating at, also if boost pressure was so high the temp in the cylinder head and exhaust manifold would be so high you would see it from your heat sensing gun.

Have you had all the coolers off, also have you cleaned the CAC matrix on the air side to make sure its free from oil mist blockage.

Thanks Paul - indeed still looking. It all comes back to a detailed temperature search around the enigne at speed and load which I will do and report back. No signs of discolouration and indeed I did strip the air charge cooler and clean the tubes and fins. Once we are nearer on the diagnosis I will come back to you - no point in wasting your time around the boat taking measurements I can do. Your job will be to help me fix it when I know what it is!!

 

[rafiki_]

The Merc 1.7s have had waste gate issues in some installations, particularly with installations susseptible to salt water. The waste gate rod can stick, causing over boosting. I have no idea if this is deviant to your problem.