351 Windsor Oil Pressure Problem

My question is about a 351 Windsor engine. On cool days (70 degrees), it runs fine and the engine temp hovers only halfway to the red zone and the oil pressure is steady. On hot days (over 80 degrees), it runs
hot and will overheat if I push it at all. When the engine idles down to 600-700 RPM, the oil pressure will dive to zero if I don't keep the RPM's above 700-800. Any ideas on how to solve this problem? What about trying a lower temp thermostat, maybe a 180? Thanks.

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CG wrote:

180 or 160 thermostat,50/50 coolant mix,slightly heavier grade oil,up the idle,check/retard the timing slightly, add a bigger radiator/electric fan



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Overheating is caused by a compromised cooling system, usually the radiator. There is absolutely nothing that a lower degree thermostat will do to help, except maybe give the radiator a bit more of a head start. That won't help for long. Get the radiator fixed.


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some of the rebuilt radiators are worse than what you may have, I got one and it razed the temp by several degrees, the paint was thicker on it, a rebuilt out of calif from the back of a mag. Best is using an intown rebuilt, check you fan clutch too, they go bad after a while oil pressure going to zero at low idal dosent sound right either.


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It's doing that because he's obviously got some bearing wear, and the oil is thin because the engine is hot.


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Bearing wear is the most comon for low idle oil pres. loss. The first thing to do on any car worth keeping is to put some acurare mechanical guages on it for Water temp and Oil Pres. Bearing wear, depending on the milage and oil used usually is the Cam Bearings on the 351W. You could try to plasti-guage the Mains and rods but you might as well plan on a re-build to be happy.Usually there is so much sludge in the oil and water passages that if dont re-build your doing more harm than good. A cheap fix would be to in the meanwhile upgrade to a high pres. oil pump.How many miles does this motor have since the last rerbuild? If your getting hot. Has it always been hot running or is this new? If it's something new, you might try some CLR in the motor wirh some water only and let it break up any lime and calcium or rust that might be blocking the passages. It only takes a small amount to block the heads water potr and your HOT.That would be to age also.
elaich wrote:




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CLR in the water and run for a while? how long, how much CLR ?
how many miles on the motor or how old ?



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Dr. Doktur wrote:

I use about normal bottle(approx. 12-18 oz.) then fill with clean water while its running to warm then use it for up to two hours then let it cool to warm and pull lower Rad hose then rad petcock and engine drain plug(Drivers side Rear By bell housing) and flush thoroughly. Usually I force water thru the heater hoses back and forth the engine and core to make sure everything is moving .Then remove your thermostat housing and flush and replace your thermostat with a 185'-190' if you are going into a cold climate and planning to have the car in the elements,and then fill with 60/40 Rust inhibitor and Quality anti-freeze. This has saved me money on radiator rot and heater core hassel.



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CG wrote:

Have the coolant tested for byproducts of combustion. If the test is positive, you have a blown head gasket.
As for the oil pressure, the first thing to do is put a real gauge on it. Factory gauges are notoriously inaccurate. If it's still low, switch to a heavier grade oil.
Lotta miles on this motor?
--
.boB
2006 FXDI hot rod
  Click to see the full signature.





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Try changing the oil pressure sensor.
I had the same exact problem when I was a kid over 20 years ago in my 1975 Cougar. At idle the pressure was zero on my gauge but there were no valve train sounds as a result of it. If your engine truly has low oil pressure the first place you will hear it is in the valve covers unless it has gone for so long it spins a bearing.




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You may want to check the oil pressure sensor and sending unit and even the guage before you diagnose it as an engine problem. If its none of those then I would check the radiator.
Erik D. No cool vehicles :(




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The engine has 150K on it. The radiator is new in terms of miles, but it is several years old, because the car is not a daily driver. Mechanical guages confirm that the pressure really is dropping. I've tried a higher pressure oil pump with heavier oil and that changes things enough the problem only happens on hot days. The problem came on pretty suddenly. Since it runs OK on cold days, I am looking for something I can do to help the engine stay cool. I think you guys are right about the cam shaft bearings being worn - an engine rebuild is sadly probably in my future. - cjg

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