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7.3L IDI Questions

TTMotorsports

Red Skull Member
Joined
Jan 7, 2021
Member Number
3315
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1,294
Loc
Lucerne Valley, CA
So I picked up a 89 F350 7.3L IDI non turbo truck and water pump and coolant was flushed out 5K miles ago. Needless to say it overheated on the way home and would continue to do so unless I left the radiator cap loose. When it was running with cap on and at temp I didn't see any leaks BUT with this being a C6 no Overdrive and 4.10 rear gears at 60mph it's at 2800 rpm which i feel is a little too high for this motor. What should i look into to see what the possible problem could be. With it cold the water in radiator isn't circulating but when up to temp it is so I feel the thermostat is working correctly. I drove it 95 miles before it overheated and the coolant was full before my trip home. Also the coolant on the shitty Ford gauge was at the N in normal and then 75 miles after driving went to O then to the R and then it spiked the gauge and shut it down when I discovered it was now out of coolant. No smoke or anything out the tailpipe either. Thanks
 
2800rpm is fine for a 7.3. It's not a 60s big block grandpa, stop treating it like one. You have a leak somewhere. It probably only leaks under pressure. The gauge did its job. You ran out of coolant. Once the coolant got below the heads you heated up the steam real good and pegged the gauge.
 
7.3idis have cavitation problems due to thin cylinders, if you cannot find an external leak the coolant could be going into a cylinder.

It's also a governed diesel, give it whatever rpm it wants
 
since we're talking about IDI's, how are the 94 7.3 idi's with factory turbo?

theres an 89 f350 with a 94 engine and trans swap somewhat near me thats cool, i know the engines are reliable but thats about it
 
Arickvan said:
since we're talking about IDI's, how are the 94 7.3 idi's with factory turbo?

theres an 89 f350 with a 94 engine and trans swap somewhat near me thats cool, i know the engines are reliable but thats about it
Click to expand...
Remember, not all 94s have turbos. Mine doesn't
 
Whats the easiest way to know if the coolant is leaking into cylinder internally? I know gas motors you can test coolant for the exhaust gas in it. But no idea on these diesels
 
posford said:
Remember, not all 94s have turbos. Mine doesn't
Click to expand...

i guess ill post the ad :laughing: ill only be a little sad if someone jumps on it before i do

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"I have here a 1989 Ford F-350 with lots of cool parts. Truck has a Dana 60 front axle, Sterling 10.5 in the rear with LSD. Motor is a lightly built 1994 IDI 7.3 with factory turbo setup. Has a zf5 manual trans as well. 4wd, airbags in the rear, 3 inch straight pipe, dual batteries, steel bumpers, Leer camper shell, brand new pillar gauges, mt tires, and beautiful interior. I love this truck and do not want to sell it, but I am in need of a quad cab or extra cab truck. The price is 8500 obo, due to the great condition and parts invested into this truck. Not interested in any trades really except for a turbo diesel with an extra cab or quad cab, and I’m willing to put cash on top. Thanks for looking"
 
TTMotorsports said:
Whats the easiest way to know if the coolant is leaking into cylinder internally? I know gas motors you can test coolant for the exhaust gas in it. But no idea on these diesels
Click to expand...
Smoke on startup or yellow/white slime under valve covers, in the oil fill things like that. Usually they will leak while it's not running though.

Is the coolant disappearing or does it just overheat?
 
Arickvan said:
i guess ill post the ad :laughing: ill only be a little sad if someone jumps on it before i do

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Log into Facebook to start sharing and connecting with your friends, family, and people you know.
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"I have here a 1989 Ford F-350 with lots of cool parts. Truck has a Dana 60 front axle, Sterling 10.5 in the rear with LSD. Motor is a lightly built 1994 IDI 7.3 with factory turbo setup. Has a zf5 manual trans as well. 4wd, airbags in the rear, 3 inch straight pipe, dual batteries, steel bumpers, Leer camper shell, brand new pillar gauges, mt tires, and beautiful interior. I love this truck and do not want to sell it, but I am in need of a quad cab or extra cab truck. The price is 8500 obo, due to the great condition and parts invested into this truck. Not interested in any trades really except for a turbo diesel with an extra cab or quad cab, and I’m willing to put cash on top. Thanks for looking"
Click to expand...

Doesn't look terrible, price is high for what I'd expect out here. Where's the ignition lock cyl in this picture? :homer:

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First off, idi's will run on the governor all day long.
Second put a fomoco statt in it!
ANYTHING else won't run right!
Same with glows ONLY ford...
Best tech forum for these is oilburners.net.

Edit as to "where's the ign lockset?" Bricks like to bust the transfer bar thus the real switch down on the column gets modded ...
 
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posford said:
Doesn't look terrible, price is high for what I'd expect out here. Where's the ignition lock cyl in this picture? :homer:

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Click to expand...
i think that the old auto shifter collar... maybe...


and ya price is high, ive messaged him and got him to come down some but not enough, hence why im not saying hey look at my new truck :laughing:
 
You can pressurize the coolant system and then inspect for coolant leaks. If you can’t maintain pressure and there are no external leaks then it’s probably in one of the cylinders. Would likely have to pull injectors and use a bore scope to try and narrow it down.
 
That thing should pull really well at that rpm....The IDIT i had would just eat all right at the governor or just under.
 
Timing set by a meter???
Btw, injectors and I.P. Are only good for round 100k.
 
Coolant dropped a little bit when driving it today but didn't put many miles on it and only got it up to temp for 15 miles. There is white smoke out the tailpipe when I start it and when I rev it up but my dad says it smells like oil. I will check the oil fill cap area for anything that doesn't look like normal oil and report back.
 
OK appears it's a common problem on these motors for the fan clutch to not work correctly and I found a thread about ading 30wt motor oil into it and fixing that. So i'm gonna try that and see if it helps.
 
Ok I locked up the fan clutch with a piece of metal i cut out to tack to the fan that has a hex that locks it all in place. Drove it harder than I did when overheated first time and no issue so seems to fix my problem. Now yo get overdrive so I can go faster than 60mph easily
 
TTMotorsports said:
OK appears it's a common problem on these motors for the fan clutch to not work correctly and I found a thread about ading 30wt motor oil into it and fixing that. So i'm gonna try that and see if it helps.
Click to expand...
Just an FYI.....on mine, just about the time I started to wonder if the fan was gonna kick in, or if I was gonna have to back off on a grade, it would kick in and drop the temp so fast it was crazy....
 
next time just drill a hole through the clutch and toss a bolt through it
much easier

on the coolant thing, all of mine will bubble out of the rad puke hose at idle, gets worse with load
the one of them I tore down had such bad rust pitting in one cylinder that I'm shocked the piston rings didn't catch on it, still ran fine and spent most of its time right on the governor. Made about a thousand bucks parting it out on ebay, btw. Rods, injectors, oil cooler and IP are the big money apparently
 
Well it appears that locking the fan clutch fixed the overheating issue I had and drove it 150 miles again and the coolant level hasn't dropped at all and oil level is the same as before.
 
Nice! google you "sca" as in 'supplimental coolant additive'

because if you don't use that shit, you will have holes in your cylinder walls soon enough
 
[486] said:
Nice! google you "sca" as in 'supplimental coolant additive'

because if you don't use that shit, you will have holes in your cylinder walls soon enough
Click to expand...

OK I'm going to drain and flush the coolant system and replace it all with new antifreeze. I have read that some antifreeze has the SCA already in it. Do you know what kind this would be to not use the green stuff + the additive
 
TTMotorsports said:
OK I'm going to drain and flush the coolant system and replace it all with new antifreeze. I have read that some antifreeze has the SCA already in it. Do you know what kind this would be to not use the green stuff + the additive
Click to expand...
Use the green stuff, with the additive. Give it a week, then test it.

You won't put holes in your cylinders for years, even without the SCA stuff.
 
Pt_Ranger_v8 said:
You won't put holes in your cylinders for years, even without the SCA stuff.
Click to expand...
who's to say the string of previous owners ain't used up most of those years?
The one I tore down with the real bad pitting? had sleeves in all 8, jasper rebuild in a '93 truck, so possibly quite a bit fresher than the OP's engine
TTMotorsports said:
OK I'm going to drain and flush the coolant system and replace it all with new antifreeze. I have read that some antifreeze has the SCA already in it. Do you know what kind this would be to not use the green stuff + the additive
Click to expand...
the hideously expensive red shit

just use the green with the additive
 
[486] said:
who's to say the string of previous owners ain't used up most of those years?
The one I tore down with the real bad pitting? had sleeves in all 8, jasper rebuild in a '93 truck, so possibly quite a bit fresher than the OP's engine
the hideously expensive red shit

just use the green with the additive
Click to expand...

You're not wrong.

a 3 pack of the test strips is like....$2. Use one to determine where it's at now.

flush/refill, add the recommended amount of SCA (1 bottle?), and test

Wait, 3-6 months, and test again.


These engines are great if you're not in a hurry, and want something stupid easy to work on.
 
Yeah I would test where it's at now but I lost alot of coolant and added 4 gallons of water to it now so I know it's not anywhere near correct now. My research shows carquest has the strips in stock. Does napa have them by chance if you know?
 
Built and “serviced” a rig that Pulled 20-25k with a non turbo idi for three years, the last year the oil never got changed an injector stuck open, it spun a bearing and tossed two rods.
 
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