Issues after rebuild :( Low oil pressure & gas smell in coolant

[BearitvRanger]

I have a problem with the old 2.9l v6 i just rebuilt for my 1989 ford ranger. after rebuild the oil pressure shoots down pretty much the same time the coolant temp starts to rise. i also noticed a slight smell of gas coming from the coolant? so far no leaks, no mix in coolant/oil. runs great, sounds great but it drops in oil pressure as soon as the truck warms up. also weak water pressure when warm. clearly something is wrong. Oil pressure is also very consistent when cold and will quickly drop. 5w30 conventional oil for first start, royal purple break oil in since, K&N oil filter

when building this I took the block, crank and new pistons to a machine shop for inspection and boring. the crank was undersized on journals & rods. new bearings are within spec. The block was bored and checked for flatness as well as hot tanked. the heads were replaced with new/remanufactured heads. valves lapped, lifters replaced. camshaft fine so it is stock. new pump.

they pulled all the plugs out for me before the hot tank and I think I might of not put one of the threaded plugs back. I've put a picture in the post with a red circle on it. this shows the coolant plugs I did put in on both sides of the block, but i was unable to find the location of the 3rd plugs home after looking over everything. the picture below is a threaded plug i got back from the shop but did not reinstall due to not finding a home for it (the plug fit well in the oil pressure sensor location).

I also replaced styles of oil sump pickups, could this effect the oil pressure when warm? picture below.

I'm pretty lost and have a lot of money into this and would like it running ASAP any input would be great!

 

[Uncle Gump]

What is the pressure on a cold start and where does it end up at a warm idle.

I would think if one of the oil galley plugs were left out... it wouldn't make much pressure cold or hot.

 

[BearitvRanger]

What is the pressure on a cold start and where does it end up at a warm idle.

I would think if one of the oil galley plugs were left out... it wouldn't make much pressure cold or hot.

Oil pressure is right in the middle, than drops to nothing as soon as it warms up. I'm thinking you are correct, any way you can elaborate?

 

[JerryC]

Gas smell in the coolant sounds like a leaking head gasket.

You need a gauge that shows the oil pressure numerically.

Does the oil pressure climb when you rev it up?

Try a new oil filter.

 

[BearitvRanger]

Gas smell in the coolant sounds like a leaking head gasket.

You need a gauge that shows the oil pressure numerically.

Does the oil pressure climb when you rev it up?

Try a new oil filter.

It's a brand new head gasket, torqued to spec. Brand new heads as well. Not saying it can't happen but I think it's unlikely.

I Also think its worth noting I installed a new all aluminum radiator when I did the rebuild, possibly the smell is cleaning agents from the new radiator.

I also bought a mechanical test gauge I'm going to try and install that tomorrow

 

[Uncle Gump]

Oil pressure is right in the middle, than drops to nothing as soon as it warms up. I'm thinking you are correct, any way you can elaborate?

Not exactly sure what you want me to elaborate... but I'm thinking you should hold judgement on this until you screw a mechanical gauge in the engine and look at some real numbers.

Oil pressure is developed by the pump delivering a volume of oil to the oil galleys. Pressure isn't developed until that flow of oil meets a restriction... (bearing/component clearances). If one of the galley plugs were not in place... it would offer no restriction... therefore no pressure.

I rebuilt a 302 years ago. The machine shop removed all the oil galley plugs for cleaning and installed new plugs before delivery back to me. I built it and installed it. I started it up and oil pressure was right at the pressure relief valve value (60 psi). I ran the engine to break in the cam.... lowered the RPM's... engine was warm... pressure was just north of 20 psi. I'm thinking perfect. I blipped the throttle a couple times to hear the roar and the oil pressure dropped to near 0. I shut it down. I let it cool and restarted it... and the engine still had near 0 oil pressure. Upon examination... one of the oil galley plugs for the lifter bores had popped out. I tapped the galley port and installed a pipe plug in it... oil pressure problem solved.

You also need to remember the oil pumps are positive displacement. Meaning the faster they turn... the more volume they deliver. So at start up... your pressure should be on or near the oil pressure relief value (most likely 55 to 65psi). Once the engine warms the pressure will fall and probably be around 20psi +/- a few. This will be dependent on how tight or loose the engine was built... the looser the lower the pressure will be. The thing to remember is that as soon as you increase engine RPM the pressure should climb.

 

[Craig0320]

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