99 cobra oil pressure at idle?
- Thread starter 99SVT1318
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How low is it ?
And the idle speed is 900 to 1000 ?
You are probably safe .
Change oil and use a ford filter .
You are probably safe .
Change oil and use a ford filter .
What did you do to get it "all fixed up " ?
If you have to run oil that heavy it's not fixed up. IMO 40 weight is too heavy for these heads. That pressure still sounds low for these engines.
Hot mine's about 25 with 5W30
Factory hypereutactic pistons do not change much in width as temperature changes (compared to conventional aluminum alloy pistons) and are close tolerance fit at the factory. There were 3 different piston ranges that were colour coded Red, Blue, and Yellow. Cylinder bores were measured and the pistons were then matched up with the cylinders to obtain a maximum Piston-to-Bore clearance of 0.026 mm [0.0010"]. This reduces cold start piston slap and oil consumption. This helped to get the low-emission rating that these engines had. One of the reasons the factory oil was 5W-20 was to reduce the likelihood of scoring the piston skirt during cold start. Although a 5W-40 has the same SAE rating, it doesn't necessarily mean that the viscosity is the same at all low temperatures. If you live where it gets cold, and drive your car all year long, be careful not to go too high on the W side.
These engines also have a problem if you run at high rpm for any extended time, of oil collecting up in the heads and not returning to the sump quickly enough. Using a higher weight oil may require running the oil level on the higher side to limit oil pump starvation, especially if you run extended high revs before full operating temperature is reached.
Crankshaft bearings are also a tight fit from the factory. Main bearing clearance is 0.025 mm to a maximum of 0.050 mm [0.00098-0.00197"] and rod bearing clearance is 0.027-0.069 mm [0.00106-0.0027"]. The reason these are so tight is that aluminum expands more with temperature than steel. At operating temperature the bearing clearance is actually more.
I'm not saying 5W-40 is bad, and I'm not saying other oils are bad. I'm just explaining some of the reasons the factory spec was the 5W-20 semi-synthetic and some things to consider before choosing your oil.
These engines also have a problem if you run at high rpm for any extended time, of oil collecting up in the heads and not returning to the sump quickly enough. Using a higher weight oil may require running the oil level on the higher side to limit oil pump starvation, especially if you run extended high revs before full operating temperature is reached.
Crankshaft bearings are also a tight fit from the factory. Main bearing clearance is 0.025 mm to a maximum of 0.050 mm [0.00098-0.00197"] and rod bearing clearance is 0.027-0.069 mm [0.00106-0.0027"]. The reason these are so tight is that aluminum expands more with temperature than steel. At operating temperature the bearing clearance is actually more.
I'm not saying 5W-40 is bad, and I'm not saying other oils are bad. I'm just explaining some of the reasons the factory spec was the 5W-20 semi-synthetic and some things to consider before choosing your oil.
The reason the 5w-20 was specified was trying to hit economy standards. The engines were identical in 99 and 01, but the 99 had 5w-30 recommended. The 5w-20 was to help mpg's.
I was told a few years ago by an engine builder that the passages in these heads are too small for a 40 weight oil. So I've never run anything heavier than 30 weight. Even in my blown big bore stroker. Aside from the rings sealing so well they sucked the oil pass the guides on decel I never had an oiling issue.
But then I believe the new GT500's and track pack 5.0's require something like 15w-50. Different heads so take it with a grain of salt.
And last but not least. Anyone that's been around these cars any length of time knows to run 7 quarts of oil because of what collects in the heads. Someone did a test on here many moons ago and it took about 9 quarts to even get close to the pan rail. So the extra quart won't hurt anything.
I was told a few years ago by an engine builder that the passages in these heads are too small for a 40 weight oil. So I've never run anything heavier than 30 weight. Even in my blown big bore stroker. Aside from the rings sealing so well they sucked the oil pass the guides on decel I never had an oiling issue.
But then I believe the new GT500's and track pack 5.0's require something like 15w-50. Different heads so take it with a grain of salt.
And last but not least. Anyone that's been around these cars any length of time knows to run 7 quarts of oil because of what collects in the heads. Someone did a test on here many moons ago and it took about 9 quarts to even get close to the pan rail. So the extra quart won't hurt anything.
Yes, the switch to 5W-20 from 5W-30 was for fuel economy. Ford had to do that on a lot of vehicles to reduce their overall corporate fuel mileage. The problem was selling too many F150s and too few cars. Ford was not the only OEM that did that.
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