I am a new diesel owner for all of 2 months and already I want to shoot it. Please excuse the long narrative but I don't know what will be relevant and what isn't. I bought a 1990 E350 ambulance for a steel of $850.00 on a government auction. It had sat for 7 or more months before I bought it. The local Ford dealer replaced the fuel lines to each injector, did the brakes etc. The dealer told me the truck had a factory rebuilt engine in it but no one knows when it was installed. The odometer shows 88,000 miles and I don't think it has been around but who knows. I drove it 300 miles to home. I literally took it back out 1/2 an hour after getting home and 3 miles later blew the rear seal. I decided to have the transmission rebuilt at the same time the seal was being replaced. Some front end work and a total of $6,000.00 later and the engine started to overheat and make a loud banging noise. The temperature went up to 230 before I was able to get it off the road and shut down. My normal gas mechanic figures it is the thermostat for the overheating and either a valve or a push rod. After speaking to other mechanics I pulled the drivers side valve cover off and everything is going up and down. With the breather off it sounds like a very loud drum tattoo. The passenger side cover has a bracket that is giving me a hard time removing so I haven't removed valve cover yet. The only diesel garage that I could get to speak to me said $700.00 to diagnose and if it is a push rod another $300.00 to finish the job. If it is a valve it would be $3,500.00. What can / should I do to try to diagnose the problem myself. At what point should I just cut my losses and turn the thing into razer blades. Needles to say my wife is ready to kill me.

Holy Hell, im glad i don't take things to the shop much any more....those prices are ridiculous. I hope that includes a happy ending on your part for 3500 for replacing valves. Anyway, a thermostat isn't that big of a deal. I'd start there....not sure about the banging. Does it do it all the time, or just when hot, or just cold, or what?

Welcome to FTE by the way!

Thanks for the response, The banging noise is all of the time. I was thinking of trying to diagnose the engine noise before I went to the hassle of removing the thermostat. From what I can see I think I have to remove the alternator to get at the Tstat housing bolts? Who thought of that idea?

Your "banging noise" could be a sticking injector. They can make some pretty good noise. With the engine running at idle, loosen one injector line at a time and see if the noise goes away. If that line makes no difference in sound, tighten it back up and go to the next one. If you find one that makes it run quiter, you have found the bad injector.

Thanks for the advice. I will get at it this afternoon. When I had an emissions test done on it they told me a 40 and below was a pass. Mine came in at a 6. The tester says it means the injectors are in good shape. I hope it is as relatively simple a diagnosis as that.

Where do you live that you havebto smog an old idi

That doesnt make any sense, I knwo the noise your speaking of...its a stuck valve....i had the same problem when I blew my aftermarket oil pressure gauge line on my 1990....does it sound like this:

7.3l knock - YouTube


I had a stuck valve on my 1990 7.3...and so i plugged my oil line gauge, then filled it with oil, and away I went.

Thanks Aune163rd. It sounds exactly like that. When you mentioned your oil gauge it reminded me that when it first happened my oil gauge went down to nothing at idle then went to high as I started to pull away. The oil level was down about 1/2 quart. So are saying I should disconnect / replace the oil gauge line and that will hopefully fix the problem. Did you have to do anything to the valve itself?

I really appreciate the time everyone is giving to this. EXSIGS

TO FORDFORLIFE7.3

I live in Toronto and it wasn't until after I had the Etest done that I found out the clerk at the license bureau was full of #@$#. That was another $80.00 I didn't have to spend.

No it just sounds like your oil consumtion is rising....i would suggest searching for leaks and cleaning your CDR vavle

Aune163: I got the valve covers off and all of the arms are going up and down. The rods all appear to moving as well. I tried to record the sound but it sounds normal on the playback. The noise I hear is identical to the one you posted. What did you do to determine what valve was stuck and how did you un-stick it? Do you know any one who might be interested in buying this unit? The engine is a factory rebuild of unknown age. The transmission is a E40D rebuilt less than 200 miles ago and it has 4 new tires.

Aune163: I forgot to ask, to clean the CDR valve do I just wash it in varsol or some other cleaner like that and let it dry before I re-instal it? Thanks

I'm not exactly sure what varsol is, but it might work. The CDR valve has a rubber diaphragm that moves back and forth. Most people soak it in gasoline to loosen the crud then flush it out well. Let it drip dry and reinstall. To test it, use your mouth to blow through the small hole in front and a finger through the back to see if the diaphragm moves. It only needs a small puff, so just use your mouth.

Thanks Techgod13. So as it stands now I have to change the tstat, clean the CDR valve and I still don't know for sure what is making the loud noise like the one that Aune163rd has in posting #8. With the valve covers off I'm not seeing anything wrong except the passenger side has more black goop than the drivers side. Am I at the point where I have to pull the head?