1989 7.3 idi thumping from intake

VIK1NG

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Hey guys, I've been lurking through these threads for years and gotten so much good info. Many thanks for that!
My issues have gotten too specific so I'm asking on my own now; I've had this f350 for a couple years now and it's been parked for the better part of 9 months while I've messed with the fuel injectors trying to eliminate this intermittent "thumping" (I've been known to call it the "womp womp"). The details of the womp really haven't changed much despite a lot of work and varying tests. I first noticed it when slowing down from freeway speeds to exit, at first (from inside the truck) it sounded exactly like an exhaust manifold ticking, but as I slowed and the engine returned to idle RPMs it became a very deep and pronounced thumping in time with engine revolutions. After some research I decided to change my injectors, since I'd owned the truck a year and hadn't done that. When I pulled them there were a couple SERIOUSLY fouled up injectors, covered in much and carbon clear up to the big threads, one that came out in half and took a couple days to pull out the bottom cup (a story and a homemade tool worth another thread by itself). So I bought remans from a reputable diesel shop, cleaned the actual devil out of each of the ports, replaced all the return lines and one high pressure line that had a cracked nut, it ran great for a week or 2, but the thumping came back like before, always after running under load for a bit, never from idling or at start up. I blamed leaky injector seats and spent a lot of time over the next months driving it very little, mostly to test it; and always pulling, cleaning, and re-seating the injectors. I finally accused the remans of having different 'pop' points, plus causing a lot of wear and tear to them conatantly pulling them and cleaning them. So I broke down and replaced all injectors with brand new ones. The truck runs so smooth and great now, until I run it at high RPMs for a few minutes, then the thumping comes back.
I have all kinds of deep fears about valves/guides, compression issues, etc. But I'm always stuck on the very specific relation to the higher heat and RPMs, if i rev it up after a cold start it doesnt do it, only after a susptained load for a few minutes. Then once the truck cools a little it sounds like an absolute dream again.. but the video I took today (see link below) is right after getting off the freeway, any ideas of what to look at first?

xc_hide_links_from_guests_guests_error_hide_media

As a probably separate issue, I've been chasing down one of the few issues that will cause the obd 1 to throw a light, I believe I have a bad coolant temp sensor, i have ordered a new one but it did this once before, I pulled it and cleaned it and it went away for months, it's back so im just replacing it now, I doubt that could be related to any of the above issues but I'm no pro.
 

Clb

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"Reputable shop"= to many rookies out there !
Look up chuff
Check timing

Sounds like a lifter tick but these things don't sound the same on film as they do in the yard!
 

IDIBRONCO

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First off. There's no OBD of any type on our trucks, enginewise anyway. The exception is for the E4OD transmission, but that has nothing to do with the engine at all and will not make a light come on. What will happen is that the "OD off" button will flash. It's been a while since I've messed with the E4OD so if I'm wrong on that part, someone will correct me. It still will not make any dash lights come on. Remember that these engines are entirely mechanical in function. The only electronics involved are the power to keep the injector pump pumping fuel and the power to operate the glow plugs. The gauge senders do take power, but they aren't required for your engine to run.
These engines do have a thump noise that comes from the intake, but yours does sound louder than normal. Try taking the lid off of the air cleaner and posting another video of how that sounds with the engine running.
One last question, does the engine still run smoothly when the noise is happening or does it run roughly like there's a miss?
 

VIK1NG

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First off. There's no OBD of any type on our trucks, enginewise anyway. The exception is for the E4OD transmission, but that has nothing to do with the engine at all and will not make a light come on. What will happen is that the "OD off" button will flash. It's been a while since I've messed with the E4OD so if I'm wrong on that part, someone will correct me. It still will not make any dash lights come on. Remember that these engines are entirely mechanical in function. The only electronics involved are the power to keep the injector pump pumping fuel and the power to operate the glow plugs. The gauge senders do take power, but they aren't required for your engine to run.
These engines do have a thump noise that comes from the intake, but yours does sound louder than normal. Try taking the lid off of the air cleaner and posting another video of how that sounds with the engine running.
One last question, does the engine still run smoothly when the noise is happening or does it run roughly like there's a miss?
I have always been under the impression that this era F Series still ran OBD-1, this is reinforced by the fact that I literally have a "Check Engine" light on my dash, that being said I have never cared to try and read a code from it because the CEL on this truck only relates to coolant temp and oil pressure from what I understand. I do have an E4OD in this truck so it's not quite as completely mechanical as I wish it was. But I digress...

I drove this truck for over a year before it did this, so it definitely isn't a normal 7.3 thumping sound at all, the thump is extremely loud, very noticeable and abnormal, and twice as loud with the filter can off. It's also ONLY after being run under load at higher RPMs.
But yes, to your question, once the thump appears in it's fullest form it does feel like a miss of some kind, not as bad as I felt it when I had bad old injectors but it doesn't have a little wobble once it starts thumping
 
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VIK1NG

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"Reputable shop"= to many rookies out there !
Look up chuff
Check timing

Sounds like a lifter tick but these things don't sound the same on film as they do in the yard!
If it were a timing or lifter issue, wouldn't it be more constant and consistent? Instead of only happening after running at high RPMs for a time? Like, if I drive around town it won't do this, only on the freeway or up a big hill.. if I drive it for 10 minutes in neighborhood or town conditions it will stop thumping, but 5 minutes at 75 mph it starts again
 

Big Bart

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Three things
1) Do as IDIBronco suggests to confirm if it’s a intake noise. If it gets louder when the air cleaner is off then it’s intake generated. Perhaps it’s timing or perhaps it’s a intake valve leaks under compression.
2) If intake related clean your CDR valve replace if marginal. Could be slapping back and forth.
3) To me based on the rhythm and sound I think it is your vacuum pump that is making the noise. But it’s a video so hard to say for sure. You could pull the belt off and confirm. Just do not drive that way as the brakes will not work much at all.
 

VIK1NG

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Three things
1) Do as IDIBronco suggests to confirm if it’s a intake noise. If it gets louder when the air cleaner is off then it’s intake generated. Perhaps it’s timing or perhaps it’s a intake valve leaks under compression.
2) If intake related clean your CDR valve replace if marginal. Could be slapping back and forth.
3) To me based on the rhythm and sound I think it is your vacuum pump that is making the noise. But it’s a video so hard to say for sure. You could pull the belt off and confirm. Just do not drive that way as the brakes will not work much at all.
It's definitely super loud with the cover off and very concentrated in the intake manifold. I am going to spend some time on it this weekend and I will definitely check out the CDR, I haven't done that yet.
I am actually super curious about the vacuum pump, you're the first person to mention that in probably 50 forums I've fished in, and I have noticed the brake power seeming really low and messed up, I just mentally added it to the list of things I need to fix someday, never occurred to me it might be related to an upper engine issue. Can you tell me more about why that comes to mind?
 

IDIBRONCO

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I have always been under the impression that this era F Series still ran OBD-1, this is reinforced by the fact that I literally have a "Check Engine" light on my dash,
Yes the gas engines do use a ECM so they do have a OBD system. Your "check engine" light is exactly the same as the "oil" light that was used in cars back in the 70's. Those certainly didn't have OBD systems and those lights were only activated by a sending unit on the engine. That's why they're called idiot lights.
At the same time, don't get the TCM (transmission control module-not to be confused with an engine control module) confused with having anything to do with your engine. It does use OBD1, but it's STRICTLY for the transmission. We're only talking about the engine here and not the transmission. The engine is entirely mechanical with no computer control at all. The same "check engine" light is also found in the same year (and earlier) trucks with standard transmissions so there's the proof that it has nothing to do with a OBD system.
never occurred to me it might be related to an upper engine issue.
It isn't. The vacuum pump is externally mounted and belt driven.
But yes, to your question, once the thump appears in it's fullest form it does feel like a miss of some kind, not as bad as I felt it when I had bad old injectors but it doesn't have a little wobble once it starts thumping
This is a clue. It's missing when it's making the loud noise. The fact that it isn't as bad after replacing your injectors is strange to me, but I don't know everything. My next suggestion would be to try a leak down test before blindly replacing more parts. That should show if it's actually a mechanical problem or not. Normally you want to replace the injector pump at the same time as your injectors. They all wear at about the same rate so you won't get the most potential out of your engine by just replacing one or the other.
 

Clb

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Lets no rule out a bad reman injector...
stethoscope the various components (google diy scope) headed out soon so
good luck man
 

Big Bart

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It's definitely super loud with the cover off and very concentrated in the intake manifold. I am going to spend some time on it this weekend and I will definitely check out the CDR, I haven't done that yet.
I am actually super curious about the vacuum pump, you're the first person to mention that in probably 50 forums I've fished in, and I have noticed the brake power seeming really low and messed up, I just mentally added it to the list of things I need to fix someday, never occurred to me it might be related to an upper engine issue. Can you tell me more about why that comes to mind?
The vacuum pump is what help supplies your power brakes, unlike a gasser where the intake vacuum does. The sound on the video had a similar sound and pace of a vacuum pump. The pump also supplies vacuum for your heat and a/c venting system. Two things effect our brakes the most. 1) Lack of vacuum from the pump. 2) The rear drum brakes not being adjusted. You should adjust your rear brakes. Then hook up a vacuum guage to the vacuum system. Less than18hg at idle your pump is bad or you have a big leak. Your brake booster could also be bad if the vacuum is good and brakes are adjusted but you have a “hard” pedal and have to shove ******* the brake pedal to get the brakes to apply.

However if your sound gets louder with the air cleaner off that is a different issue to look at. You likely have a bad cdr, intake valve, or injector.
1) Start with the CDR valve. You could run for a minute without it. See if the noise stops. But clean it out with brake cleaner before replacing it. Or just replace it.
2) Do a compression test. Harbor Freight has a inexpensive kit. Hook a battery charger up while doing the test. Unplug the IP solenoid so the injectors do not inject during the test. Some had to shorten the HF glow plug adapter to allow it to thread into the gp hole. You will understand when you pull the glow plug and put it in. If you have a bad valve a) Should show as a lower compression. b) Should make the noise while cranking the engine. (Injector will not be injecting because the IP solenoid is disconnected. Thus the injector can not be knocking even if it is bad.)
3) It could be a bad injector. Rule #1 on this site, never assume a new or rebuilt part works out of the box. You can just loosen one injector line at a time while running till the noise stops. You need to loosen the line nut at the injector a couple turns and tug up on the line to break the seal sometimes. Wear safety glasses and gloves as the diesel can squirt under pressure. Tighten the line nut snug tight not Hulk tight or you may damage the line. You can tighten more if it is leaking later.

Take some pics and post. Tells us what you find.
 
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CBRF3

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Hey guys, I've been lurking through these threads for years and gotten so much good info. Many thanks for that!
My issues have gotten too specific so I'm asking on my own now; I've had this f350 for a couple years now and it's been parked for the better part of 9 months while I've messed with the fuel injectors trying to eliminate this intermittent "thumping" (I've been known to call it the "womp womp"). The details of the womp really haven't changed much despite a lot of work and varying tests. I first noticed it when slowing down from freeway speeds to exit, at first (from inside the truck) it sounded exactly like an exhaust manifold ticking, but as I slowed and the engine returned to idle RPMs it became a very deep and pronounced thumping in time with engine revolutions. After some research I decided to change my injectors, since I'd owned the truck a year and hadn't done that. When I pulled them there were a couple SERIOUSLY fouled up injectors, covered in much and carbon clear up to the big threads, one that came out in half and took a couple days to pull out the bottom cup (a story and a homemade tool worth another thread by itself). So I bought remans from a reputable diesel shop, cleaned the actual devil out of each of the ports, replaced all the return lines and one high pressure line that had a cracked nut, it ran great for a week or 2, but the thumping came back like before, always after running under load for a bit, never from idling or at start up. I blamed leaky injector seats and spent a lot of time over the next months driving it very little, mostly to test it; and always pulling, cleaning, and re-seating the injectors. I finally accused the remans of having different 'pop' points, plus causing a lot of wear and tear to them conatantly pulling them and cleaning them. So I broke down and replaced all injectors with brand new ones. The truck runs so smooth and great now, until I run it at high RPMs for a few minutes, then the thumping comes back.
I have all kinds of deep fears about valves/guides, compression issues, etc. But I'm always stuck on the very specific relation to the higher heat and RPMs, if i rev it up after a cold start it doesnt do it, only after a susptained load for a few minutes. Then once the truck cools a little it sounds like an absolute dream again.. but the video I took today (see link below) is right after getting off the freeway, any ideas of what to look at first?

xc_hide_links_from_guests_guests_error_hide_media

As a probably separate issue, I've been chasing down one of the few issues that will cause the obd 1 to throw a light, I believe I have a bad coolant temp sensor, i have ordered a new one but it did this once before, I pulled it and cleaned it and it went away for months, it's back so im just replacing it now, I doubt that could be related to any of the above issues but I'm no pro.
pull valve covers off you may have a broken rocker early motors had the aluminum lockdowns and later ones had the steal ones the early ones often broke causing 1 valve or both or a cylinder to not function properly this is something have come across many times or simply you got a bad intake valve and worst case stuck intake valve that kissed a piston sometimes we get carbon build up on the intake valves from the CDR valve that causes the intake valve to stick or get a chunk of carbon wedging the valve open. There is also the chance you had a lifter explode or collapse have seen both on our motors also sometimes they pump up and wont bleed down making a valve stand partially open neglect is usually what causes this aka lack of oil changes and bad fuels fouling the crankcase oil.
 
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