Questions and Answers
F-250 Diesel Hisses
Q. Dear Mr. Ciulla, I have a 1999 Ford F-250 Super Duty 4x4 with the 7.3 liter Powerstroke Turbo Diesel engine. I have recently noticed on start up that there is a hissing noise similar to a vacuum leak that dissipates after the engine warms up.
The hissing noise is cyclic and not constant and causes a noticeable drop in engine idle and loss of performance when I begin to drive before it is fully to temperature. I have replaced the fuel filter to no avail and my fuel economy has dropped.
Any ideas as to the problem that I can explain to the Ford Service Center before scheduling a service checkup so that I have some advance knowledge and do not get steered into an expensive solution?
Best regards,
KeithA. I don't know what part of the country you live in, but the symptoms you describe are indicative of fuel gelling. The fuel actually turns into the consistency of Jello. This is a common problem with diesels because diesel fuel contains paraffin which hardens as it gets cold.
Most fuel suppliers go to a winter grade of diesel fuel that has less paraffin and reduces the fuel gelling. You can also put in a diesel fuel anti-gel that will keep the fuel from gelling up.
Another thing to check is the air filter. Pop the top off the air filter housing and see if the air filter has collapsed. If it has then you will need to get a modified air filter housing and air filter from Ford. This has been a problem for the 1999 - 2001 Super Duty F series and Excursions.
Added From Gary:
I read the question about the 1999 powerstoke that hisses, has lack of power until it warms up and I just solved it after three dealers said they had no idea.
I have a 1996 Powerstroke and the temps in Idaho are at and below zero for the last couple of months and the problem goes beyond that. If it's real cold the max speed is 20 mph for a half mile or so and you're blowing black smoke. The hissing is from the exhaust backpressure valve (EPV).
It is a butterfly valve located in the exhaust by the turbo and it's purpose is to close when the engine is cold allowing the engine to heat up faster. Temperature is monitered by engine temperature, oil temperature, air intake temperature. The computer then opens and closes the valve. If there's an emergency and you don't have time to allow the truck to warm up, then the valve opens from the exhaust pressure and hisses and the engine RPM will pulseate until it comes up to temperature.
I've been told by some that I needed a new turbo pedestal as the actuator is in that. Others said the throttle linkage is binding.
I finally went to a fourth dealer and the first thing the Service manager asked was where the temp gauge needle sat. My truck has always registered at the low end of normal. But I told him it was lower than it used to be but the weather was cold so I just figured it was that. The problem is nothing more than a stuck open thermostat. I replaced it (for $10.00) and solved the problem along with the transmission shifts better and I went back to 17 mpg instead of 15 because the computer controls all of it.
I hope this helps others who have this problem before a dealer or someone else charges them for hours of troubleshooting and unnecessary parts.
Gary
Additional Information provided courtesy of ALLDATA
