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Discussion Starter · #1 ·
Got a weird one; hope someone can suggest a good next step.

My '95 7.3 PS was overheating (red dash light) so I pulled over. Coolant in the reservoir, radiator hot, fan seemed OK. Tried to rejoin traffic (going uphill) but no power. In park I blow black smoke if I hit the accelerator.

Start testing stuff. Only code P0472 (exhaust back pressure). Test MAP it's ambient pressure (no boost). Check MAP hose. Hook up manual gauge to hose: slight negative boost on acceleration. Take off intake boot from turbo. Spins fine. Spins when idle. There is no intercooler so just a y-pipe to the intake manifold. No apparent tears in the y-pipe boots.

I'm scratching my head at this point. I'm considering taking off the y-pipe and putting my hand over the turbo on acceleration to see if there is pressure but not sure I can reach both the pedal and turbo.
 

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You can always pressurize the MAP through the hose and see if it responds with the correct frequency output. See the attached. For the pin references use the 49-state referenced pins (disregard the Econoline/California stuff). Cheers!
 

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Sounds to me like there is a blockage somewhere. Also, trying to test the boost while parked is not likely to be fruitful in that you cannot really put the engine under enough load to develop much/any boost.

you didn’t recently have things apart, and leave a rag somewhere to keep dirt from intruding into a plenum?

What about the total failure of exhaust manifold or up-pipe or joints thereof?
 

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Discussion Starter · #4 ·
I ended up taking the y-pipe off and seeing if the turbo was blowing air, which it was. I put it all back together and not sure whether to keep driving since I won't be able to see the smoke in the dark.

No blockage, no tears. Also no wastegate or intercooler so who knows.
 

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Discussion Starter · #7 ·
I drive down to where I can at least get a wink of sleep. It was all downhill so difficult to gauge the overheating issue. I found some light at a fire station and if I hit the accelerator (in park) it will initially blow black smoke then it will dissipate.
 

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Discussion Starter · #8 ·
I have a hydra so I could get my shift points back. Been running it for years on the same program.

Everything kinda went to heck after going up a steep road in 4lo. Engine overheated a little. This engine used to always keep very cool and I never had an overheating issue until that really steep hill. Also driving through the Rockies I've been revving a lot. If I don't figure this out I'm not getting back over these mountains!
 

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There is a temperature sending unit for the gauge (on top of the pump housing) and a temperature switch down nar the CPS) for the overheat idiot light. You are correct that they are independent from one another. Cheers!
 
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Discussion Starter · #16 ·
So I borrowed a shop vac to pressurize the exhaust and found a leak where the up pipe connects to the exhaust manifold. Hope tightening the bolts fixes that otherwise I'm not sure how to fix.

It's going slow because I'm banged up with a hip contusion and a broken foot.
Automotive tire Gas Automotive fuel system Automotive wheel system Auto part
 

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High egt's would take a some time to affect engine temps. Have you made sure that your ac condenser and radiator core are clean. Can't begin to tell you how much dirt, mud and leaves I have found between the condenser and radiator on different trucks. Also I believe it was already mentioned but make darn sure your fan clutch is good and you don't have a lower radiator hose that is collapsing. If you shut the engine off at operating temperature the fan should stop spinning almost as fast as the engine shuts off, if the fan continues to spin for several seconds after the engine stops you need a fan clutch
 
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From the factory the manifolds have no gasket, but they are available (F4TZ-9448-A). You may need to see if the manifold surface is flat as well. I would also use new bolts as well (M8-1.25 x 30, F4TZ-9S425-A). Cheers!
 
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