94 Ford 4.6L delayed oil pressure on start up

buckler2

I have a 94 Ford Thunderbird with a 4.6L engine. During start up I have zero oil pressure for 15 to 30m seconds when the car sets over night. Once the pressure kicks in the lifters quiet down and the pressure appears normal. The problem does not re occur during the day but it's the same thing the next morning. I decided to have the engine overhauled, long block, but the problem persists. It's like the the oil pump has lost it's prime. Is there a check valve in the system that could be failing? Incidently I discovered in the overhaul process that the cam shaft bearings were badly scored. I would appreciate your comments on this subject. My I mail address is Rlbuckler@Aol.com

Mr_Shiftright

Well, somebody screwed up something, I'm afraid. Yes, you could have an oil pump defect or more likely a pickup tube problem. This lack of pressure is simply unacceptable on a new long block.

I'd bring it back to the rebuilder/installer immediately....if you continue to drive it, they'll start blaming you for everything!

alcan

It could be something as simple as the oil filter. Some lower cost oil filters don't have an anti-drainback valve, which will (you guessed it) allow the oil to drain down from the top end of the engine. Try an OEM or premium aftermarket filter.

kinley

Our 94 Towncar 4.6 and 95 T Bird 4.6 both use NAPA Gold oil filters. Only the T Bird is noisy at start up, but for only 2 or 3 seconds. How come? 91,000 on TC and 41,000 on TB.

Mr_Shiftright

Well, 2-3 seconds noise is a LOT different than 30 seconds. I could see how the oil filter issue could affect lifter noise for a brief moment (good suggestion!), but I don't see how it would take 30 seconds for oil to get back up to the lifter area if it had all drained into the pan and out of the filter.

Some cars are just a bit noisy for a few seconds, especially as they age. Internal design, I think. Audis/VW come to mind.

adc100

when they installed the oil pan they over-gooped the sealing area on the block. The excess silicon promptly clogged the oil pump pickup tube screen. Another piece of information as alcan suggested is the lack of drainback valve on the oil filter. If the filter is horizontal this is a problem. Also Ford likes to use that large filter which takes time to fill. Maybe the filter on the Towncar has a vertical filter, in which case a drainback valve is not needed. (This also happened to me) Just one of my many Ford stories-sorry. I'm betting on one of these answers. Better get it looked at fast.

Mr_Shiftright

Oh, yeah, that's one I forgot.....globs of silicone sealant have killed many an engine. Mechanics should really know better. It's surprising how often I see this stuff overused...and it is deadly if it plugs an oil galley.

alcan

Wait till you see what it does to automatic transmission valve bodies. Finds it's way past the filter then disaster, considering most valves have about .0006" clearance in their bores.