Community Forums

ronspradley · 05-20-2014, 07:02 PM

My 1993 Gulfstream has the B5.9 Cummins, no electronics. I have it in the shop because it puts out a big puff of smoke off of idle, and runs hot when driving up a good grade. Radiator clean inside and out. I keep RPM up when climbing to keep manual fan churning. Mechanic called today, said problem is bad exhaust manifold gaskets. And that that is making it run rich and causing running hot. And of course that would make turbo not helping much, which would make engine work harder climbing and also make it run hot. So, the question? Does this sound like the mechanic is on the right track? Should I be looking at anything else? I have very little experience with diesel engines. Thanks for the help.

ronspradley

.

MnTom · 05-20-2014, 07:14 PM

I can't say as I would totally agree with him without seeing it myself, but it actually sounds more like a boost leak to me. That is what my truck does when a boot was leaking right off the turbo. Have him replace the gaskets and see what it looks like.

ronspradley · 05-21-2014, 12:02 PM

Checked today and mechanic says it is cracked exhaust manifold, not gaskets that are causing the leak. Give or take $800.00. If no studs break during removal process. Then we get to see if he was right.

ronspradley

.

PushedAround · 05-21-2014, 12:11 PM

I don't understand the "run rich" part. Diesels do not rely on a stoichiometric air/fuel ratio like gas engines do. They burn whatever fuel you give them with the air that's available. If there is not enough air then they will produce soot due to the un-burned fuel, but I am not sure how that would make it run hot.

Skip426 · 05-21-2014, 12:14 PM

Ron, cracked manifold can lead to a host of performance problems, low boost & running rich , so while you're waiting on the outcome of the manifold replacement, I'll throw in one more thing for your consideration.
When I took my Dodge/Cummins training in 93, the instructor warned us about the dangers of crankcase over fill; oil consumption , exhaust smoke , increased slobber and over heating. Just something to keep in mind if the exhaust manifold replacement doesn't cure all your problems.

ronspradley · 05-21-2014, 12:29 PM

Quote:

Originally Posted by Skip426

Ron, cracked manifold can lead to a host of performance problems, low boost & running rich , so while you're waiting on the outcome of the manifold replacement, I'll throw in one more thing for your consideration.
When I took my Dodge/Cummins training in 93, the instructor warned us about the dangers of crankcase over fill; oil consumption , exhaust smoke , increased slobber and over heating. Just something to keep in mind if the exhaust manifold replacement doesn't cure all your problems.

I have not over-filled crankcase when changing oil. Now what happened before I purchased in 2010 is anyones guess. If dipstick is correct, oil level is OK. No excess slobber tube output. I put hose extension on existing tube and ran it to back bumper and there is not an excess of slobber there now. I did have a dirty radiator when I first got coach. After this forum told me about slobber tubes and dirty radiators and overheating and such (thank you IRV2), I have not had running hot problems except as I said earlier, under a real heavy load. I am running Amsoil 15/40 and it uses no oil. But I will of course not know until it is repaired and I get it back on the road if this is the fix. Sure hope it is. I do not have a thousand dollars extra laying around to fix something that is not broke.

Thanks to all for the help.

ronspradley

.

PushedAround · 05-21-2014, 01:08 PM

Like others have said, if the manifold is cracked (or the gaskets are leaking) then you do have a problem that needs to be fixed. Whether or not it fixes your overheating is something that you will find out. Maybe your overheating on the hills is due to a lack of power which means that you have to run at wide open throttle for a longer period of time than you normally would. Or if you are dumping a lot of hot exhaust out, it could be affecting the temperature of the ambient air going through your radiator, again raising the temps. But this last one is really just a SWAG.

ronspradley · 05-21-2014, 08:54 PM

Need the MH for a bedroom this weekend so I am taking out of shop, parts will not be here in time to fix before this weekend. So will be in shop again, probably next Tuesday. This setup has no exhaust gas temp gauge, nor a boost gauge. Would this be the time maybe to add, while the engine is apart with the exhaust manifold off? How much money would these mods cost?

ronspradley

.

MnTom · 05-22-2014, 03:11 PM

Quote:

Originally Posted by PushedAround

I don't understand the "run rich" part. Diesels do not rely on a stoichiometric air/fuel ratio like gas engines do. They burn whatever fuel you give them with the air that's available. If there is not enough air then they will produce soot due to the un-burned fuel, but I am not sure how that would make it run hot.

It is because of the energy in the fuel. A diesel engine will run hotter when more fuel is injected with less air. With an exhaust manifold leaking the drive pressure to make the turbo run at the optimum speed is leaked out causing it to smoke and cause the exhaust gas temperature to run higher. Once the turbo is up to speed and moving the correct amount of air the same amount of fuel is "leaned out" since there is more air forced into the cylinder making the flame cooler..