351M temp fluctuating
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351M temp fluctuating
I've seen a few threads in the 73-79 forum on the 351M running warm but unfortunately have been unable to find them. Can someone point me to an appropriate thread or give some suggestions on how to remedy the following problem?
77 F150 4x4 351M C6 (both rebuilt but no mods other than aftermarket air cleaner).
Truck cranks and runs fine though it probably needs a tuneup. Water pump was leaking so I replaced it with a reman unit from O'Reilly's. Typically runs with the needle about 1/3 of the way from the C to the H but occasionally it will wander over 3/4 of the way to H, then maybe go back. When I bought it, I drove it about 9-10 hours straight without noticing the problem. Didn't start happening until I changed out the water pump. I read somewhere on here that you had to "burp" the system to purge air? What's that about?
Sorry for reposting what's been posted before, but I did some searches in both the 73-79 and 335 series engine forums and couldn't find the thread I remembered. Any help would be appreciated. Thanks!
77 F150 4x4 351M C6 (both rebuilt but no mods other than aftermarket air cleaner).
Truck cranks and runs fine though it probably needs a tuneup. Water pump was leaking so I replaced it with a reman unit from O'Reilly's. Typically runs with the needle about 1/3 of the way from the C to the H but occasionally it will wander over 3/4 of the way to H, then maybe go back. When I bought it, I drove it about 9-10 hours straight without noticing the problem. Didn't start happening until I changed out the water pump. I read somewhere on here that you had to "burp" the system to purge air? What's that about?
Sorry for reposting what's been posted before, but I did some searches in both the 73-79 and 335 series engine forums and couldn't find the thread I remembered. Any help would be appreciated. Thanks!
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Depends when it was wandering really, if it's 1/3 on the highway, then wanders when you sit in traffic it's normal. Or if it's cool at high rpm and hot at low rpm that's pretty normal too. Do you have a fanshroud? That's important. Make sure your waterpump is a direct replacment, does it flow the same gph? You do need to burp it, as long as the rad cap is the highest place on the engine all you have to do is keep the cap off while the engine runs and fill her up to the top and watch for her to bubble the air out, after a few minutes you can be sure that there is no aire and you can top it off and go. You have a overflow/reserver tank on the RAD right?
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I do have a fan shroud. As Torque said I do not have an overflow system. Problem is intermittent, not a function of sitting still or moving. I'll check the level and burp the system and see if that takes care of the problem. But it'll have to wait till tomorrow....
thanks!
thanks!
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From: Santa Barbara
Are you sure you just don't have a case of the infamous Ford wandering gauges. Mine does that every once in a while, too. The oil pressure and gas guage go up at the same time so if they all go up, I know everything is normal. I'm told it's a voltage regulator that is behind the dash and is just for the gauges.
Also, you can add an overflow. It's $10 new for one of those generic ones and takes about 15 minutes to install.
Also, you can add an overflow. It's $10 new for one of those generic ones and takes about 15 minutes to install.
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None of the other gauges wander at the same time and it didn't do it on my 9 hour Odyssey driving it back from NC at 75 mph (except for crawling through Knoxville, TN in a traffic jam). Only started after replacing the water pump. I'm going to double check the level, make sure the system is well-burped and report back later. And thanks for the tip on the generic overflow. Not sure I need one, but worth knowing.
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The guages work on a Pulsing Signal "Ground out" sending unit.
Try R & R'ing the Sending unit first.
Make sure you use a minimal amount of teflon tape or better yet the liquid tape when re-installing.
As long as there is coolant touching the SU ...the SU and gauge should work within their tolerances.
Try R & R'ing the Sending unit first.
Make sure you use a minimal amount of teflon tape or better yet the liquid tape when re-installing.
As long as there is coolant touching the SU ...the SU and gauge should work within their tolerances.
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I put an overflow on mine, funny thing is, i can't imagine how these trucks worked without them, considering when i ran on a 90* day in traffic it really filled up.
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I ran it for a while with the rad cap off--no bubbling. Temp came up normally and did not go high. I guess I need to clarify when I say fluctuating, I don't mean switching back and forth. The temp just rises and stays high, then might go back down, or might not. I don't drive it much right now cause I'm repairing and prepping for paint. So far, it has only gone high when I was driving it and it did not seem dependent on RPM or vehicle speed.
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Next time it goes high...check the other gauges at the same time to see if one of them goes high as well.
There is a crink in the Ford gauges where sometimes 2 gauges almost PIN themselves while you are driving.
I have stopped twice because of the HIGH Temp gauge only to figure out the engine wasn't overheating. see post #5 for a mention of this condition
There is a crink in the Ford gauges where sometimes 2 gauges almost PIN themselves while you are driving.
I have stopped twice because of the HIGH Temp gauge only to figure out the engine wasn't overheating. see post #5 for a mention of this condition
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Took my kids out for a ride this afternoon and experienced the problem again. Truck warmed up OK, thermostat opened, temp moved up to about 1/4 of the way to H. The more I drove it, though, the more it heated up. It never got over 3/4 of the way to the H which was a relief, but it wasn't running that warm before I put the new pump in--temp was pretty constant around the 1/3 mark.
I checked the belt when I got home--looks and feels tight enough. Don't think there's any slippage. And I don't have simultaneous gage problems as described above.
Can a radiator shop determine if I've got adequate flow from my current water pump?
I checked the belt when I got home--looks and feels tight enough. Don't think there's any slippage. And I don't have simultaneous gage problems as described above.
Can a radiator shop determine if I've got adequate flow from my current water pump?
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So far, it's only gotten to the M or A but it seemed to want to get warmer the more I drove it so I cut the joyriding short. I should also mention that it tries to keep running when I shut off the ignition when it is running warm. Doesn't do it when the temp stays at normal levels (between O and R).
ps. was I really supposed to answer that question or was that just a sarcastic way of telling me that my temperature fluctuations are NORMAL?
ps. was I really supposed to answer that question or was that just a sarcastic way of telling me that my temperature fluctuations are NORMAL?
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That my friend was a bonafide question.
Hot on these trucks is when the Gauge Pins to the right.
when the needle touches the M or A that's usually when the T-stat opens
Ford guages IMO suck.
The only real way to determine the exact temp is to put a cany thermometer in the rad cap hole.
An alternative is aftermarket "degree reading" temp gauge would also help.
IMO, that engine is not running warm.
Hot on these trucks is when the Gauge Pins to the right.
when the needle touches the M or A that's usually when the T-stat opens
Ford guages IMO suck.
The only real way to determine the exact temp is to put a cany thermometer in the rad cap hole.
An alternative is aftermarket "degree reading" temp gauge would also help.
IMO, that engine is not running warm.
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From the Haynes manual:
15 Engine 'diesels' (continues to run) after switching off
15 Engine 'diesels' (continues to run) after switching off
- Idle speed too fast.
- Electrical solenoid at soide of carburator not functioning properly (not all models).
- Ignition timing incorrectly adjusted.
- Air cleaner valve not operating properly.
- Excessive engine operating temperatures. Probable causes of this are; malfunctioning thermostat, clogged radiator, faulty water pump.