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1997 Ford F-250:
Knock when Engine Started Cold

By
Alex Steele
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as seen in Truck Trend

Question:

 

I thought it was very interesting to see that Ford was increasing production of the 5.4-liter when they have yet to find out what's wrong with some of them. I've never been as satisfied with a vehicle as I was with my light duty '97 F-250. But when the 14,000 mile mark rolled around I started to hear a very pronounced knock when the engine was started cold.

 

I received a copy of a fax from Ford that they have received the same complaint across the Triton line of engines. Ford has yet to find out what the problem is after eight months. My dealer mechanic was guessing piston slap. The knock goes away a few seconds after the oil pressure has reached its peak. I, and other mechanics I've talked to, seem to think that it would take a sloppy fitting piston longer than 10 seconds to heat up and expand, pointing possibly to a bad bearing.

 

Answer:

 

You certainly had a technician with a good ear listening to the cold start knock in your 5.4-liter at the dealership. I've spoken to a couple of Ford Techs myself, and received similar responses about this mysterious noise which is currently being worked on by the manufacturer. So I made a few phone calls, and with the help of Ford Public Affairs, I was able to get in touch directly with the engineers in Detroit who are handling the problem. I spoke to the Triton Engine Programs Manager Pete Dowding and Supervisor Bob Moore.

 

The word is to sit tight because the noise has been diagnosed, and a Technical Service Bulletin will be released shortly. They referred to the condition as a "piston to cylinder bore phenomena". It's actually a piston slap condition emanating from the anti-thrust side of the piston while below TDC (Top Dead Center). Yes, it is an unusual piston knock heard only in Park or Neutral, and then going abruptly silent after a short period of run time. The typical symptoms of excessive piston to cylinder bore clearance would be a knock dissipating slowly as piston temperatures rise while increasing with the application of torque. The service bulletin will be relevant to the complete line of Triton engines from '97 to '99 (4.6L V8, 5.4L V8 & 6.8L V10). Ford is estimating that only one out of every one thousand will be affected.

 

Unfortunately the repair is going to involve some major engine work comprising the replacement of all eight or ten pistons. The updated pistons have received the appropriate dimension adjustments in order to nullify the knock. The good news is that Ford engineering is confident that the minimal piston slap will not, and has not, inflicted any damage on the cylinder walls.

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Comments:

TechHelp2
24 Apr 2018, 08:16
RE: Jerry Guidry, There also maybe an exhaust leak at the exhaust manifold, sometimes a bolt breaks and it sounds like a knock but almost goes away when it is hot.
TechHelp2
24 Apr 2018, 08:09
RE: Jerry Guidry, without hearing the knock it is hard to diagnosis it. But from what you are telling me is the knock is only cold and runs like a top.

The knock is likely from what they call piston slap, the piston slaps the cylinder wall until heat expands the piston to fit better and it goes away. Engines can run forever with this condition. It can be repaired by a process called knurling the piston but that requires the engine to be disassembled. There are other processes but they all require engine disassembly. With 180,000 plus miles Ford will do nothing to help you financially.

The best thing you can do is continue to maintain the vehicle the best you can and enjoy the vehicle until you decide to get a newer vehicle.
Jerry Guidry
18 Apr 2018, 08:53
I have a 97 E250 Van with 180k plus. Runs like a top. But these knocking symptoms go back as far as I can remember - lately it seems to be more pronounced. Will Ford dealers be able to correctly diagnose and repair it ? And will Ford Co. be responsible financially ?

 

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