Bogging Down
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New User
Joined: Feb 2004
Posts: 11
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From: Cleveland, Oh
Bogging Down
I have a 70 f100 sport custom. I purchased it a couple of months ago, and have not had a chance to do any work on it yet. I live in Ohio, and bought it in Penn. about an hour and a half away. It drove home fine, and I took a couple of runs to the store with it since. A couple of weeks ago, I was on the freeway doing about 60 mph when the truck started to bogg down and slowed way down and started making a "Wooa Woooaa Wooaa" sound. With the pedal down to the floor, it was only doing about 30 mph. I got off the free way and it was running ok on the side streets doing about 25-35. I havent driven it since. Any ideas? I thought perhaps it was a dirty carb, but the guy I got it from replaced the carb with a remanufactured stock carb, and it is clean as a whistle. Thanks for any trouble shooting and advice.
Postmaster
Joined: Apr 2002
Posts: 3,613
Likes: 6
From: Coal country
Classic symptoms!
1. Clogged exhaust system. I had a '74 catalytic converter eat itself for lunch, and spray all the chunks into the muffler. Along with the pieces was a metal wire mesh, with pieces caught in it. When the exhaust pressure went up, as on the freeway, it would slowly compress until it was a tight wad, and choke off the exhaust. Made that Waaoooh sound you describe. Once the pressure was relieved, the mesh expanded, and allowed the gasses to escape, and it ran OK, at idle and at less than 25 MPH. Took forever to figure that one out!
2. Clogged fuel filter, and/or clogged fuel pickup tube. Check this out first, and see if that fixes it. Blow back through the fuel line from the pump (with LOW air pressure and the cap off!) and see if that helps. You may need to change the filter several times, and may have to flush that tank. Put a filter in FRONT of the pump as well. If ou can get the clear plastic cheap type, so much the better, it will show you the crud.
1. Clogged exhaust system. I had a '74 catalytic converter eat itself for lunch, and spray all the chunks into the muffler. Along with the pieces was a metal wire mesh, with pieces caught in it. When the exhaust pressure went up, as on the freeway, it would slowly compress until it was a tight wad, and choke off the exhaust. Made that Waaoooh sound you describe. Once the pressure was relieved, the mesh expanded, and allowed the gasses to escape, and it ran OK, at idle and at less than 25 MPH. Took forever to figure that one out!
2. Clogged fuel filter, and/or clogged fuel pickup tube. Check this out first, and see if that fixes it. Blow back through the fuel line from the pump (with LOW air pressure and the cap off!) and see if that helps. You may need to change the filter several times, and may have to flush that tank. Put a filter in FRONT of the pump as well. If ou can get the clear plastic cheap type, so much the better, it will show you the crud.
Lead Driver
Joined: Jan 2003
Posts: 9,893
Likes: 12
From: Ohio
I would start it up and see what kind of exhaust pressure you get out the tailpipe. It does sound like maybe your muffler got collapsed inside and is restricting it big time. Since no cats on old trucks, it must be the muffler(unless someone put one on it?)
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
A plugged exh system engine will run hot, Check exh heat raiser left manifold
if it has one. Pull carb. line off and crank eng about 15-20 sec. check gas flow volume test at pump, remove >coil wire< should be around 1/2 pint or so.
Check filter on fuel pump if it has one, screws on to pump. Check for a bad coil any loose wires. When was the last time you gased it up? Was it running good before that? What octane type of gas did you put in it and did you used a unlead additive, if no additive plus low octane this could be your problem.
my 2 cents..
orich
if it has one. Pull carb. line off and crank eng about 15-20 sec. check gas flow volume test at pump, remove >coil wire< should be around 1/2 pint or so.
Check filter on fuel pump if it has one, screws on to pump. Check for a bad coil any loose wires. When was the last time you gased it up? Was it running good before that? What octane type of gas did you put in it and did you used a unlead additive, if no additive plus low octane this could be your problem.
my 2 cents..
orich
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New User
Joined: Feb 2004
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From: Cleveland, Oh
I think I actually used a higher octane gas last time I filled up. I did notice however that my temp guage got hot really quick. I forgot to mention that in my original post. It seemed like after the truck was running for about 10-15 min, the temp guage was almost all the way to the right. So an exhaust problem you think?
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
Maybe it could have been a stuck thermostat or a sticking one, or
very low on coolent level.
1. Check for a loose fan drive belt or bad fan clutch if it has one.
2. I would replace thermostat, check new one works before installing
it in boiling hot water.
3. Wire open heat riser if it has one, left exh manifold.
4. Now start it up and just let it run. Watch the temp ga. until it
warms up. the temp should not stay above middel of ga. if it does
maybe the radiator need cleaning... Any way if all checks out ok
take it for a close short drive and keep an eye on the temp ga...
Next hwy test. ...Ps if you don't use a gas lead additive it is sure a slow death of you engine, with the only fix will be is to rebuilt the heads
with Hard Seats..my 2 cents
orich
very low on coolent level.
1. Check for a loose fan drive belt or bad fan clutch if it has one.
2. I would replace thermostat, check new one works before installing
it in boiling hot water.
3. Wire open heat riser if it has one, left exh manifold.
4. Now start it up and just let it run. Watch the temp ga. until it
warms up. the temp should not stay above middel of ga. if it does
maybe the radiator need cleaning... Any way if all checks out ok
take it for a close short drive and keep an eye on the temp ga...
Next hwy test. ...Ps if you don't use a gas lead additive it is sure a slow death of you engine, with the only fix will be is to rebuilt the heads
with Hard Seats..my 2 cents
orich
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New User
Joined: Feb 2004
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From: Cleveland, Oh
Here is an update. I went and checked it out yesterday, and I don't think it is the exhaust. There was a strong flow comming out of the muffler. One thing I noticed is that the temp is getting WAY to hot WAY to fast. I just had it idleing for about 15 minutes, and the temp guage got almost all the way to the "H" side of the guage. I was thinking maybe I need to replace the thermostat, which I will probably do just becuase it couldnt hurt, but I noticed that the coolant was getting hot (between the radiator and the thermostat). Any ideas guys?
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Thread Starter
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New User
Joined: Feb 2004
Posts: 11
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From: Cleveland, Oh
Just replaced the thermo yesterday with a Motorad Failsafe 180. Engine still got pretty hot after just idling for 15 minutes, but after a short drive around the neighborhood it lowered a little bit to just above half way. Haven't taken it back on the freeway yet, so i dont know if it will continue to bog down. Next step is removing the muffler to see if this helps with the temp problem.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
I don't think back-pressure is your problem. Here's the main things water pump impellars some very cheap one were stamp steel! The good one's were cast iron. The stamped steel one would rust out if a person use Water for coolant..Next when a person did not use Distilled water to make the 50/50 antifreeze mix long term will end up clogging off the tubes in the lower part first of the Radiator then tubes at top tank. So if it looks like just a little around the top tank tubes it's double crusted around the tube in the lower tank.It maybe time to have the Radiator clean and rodded out.. And there's also back flushing your cooling system if it needs it. Check Compression in each cylinder.. 
My truck did the something yours is doing,
the fix was to have the harden seats put in for the unleaded gas and still have to run the high octane gas.. Ps Check at night to see if your exhaust Manifolds are red hot= TO much back-pressure will do this in most cases..
my 2 cent's, hope this helped you in some way
orich
My truck did the something yours is doing, the fix was to have the harden seats put in for the unleaded gas and still have to run the high octane gas.. Ps Check at night to see if your exhaust Manifolds are red hot= TO much back-pressure will do this in most cases..
my 2 cent's, hope this helped you in some way
orich