We have a 98 Honda prelude with H22A4 motor (Automatic.....i know). We bought the car with a blown head gasket, took the head off had it resurfaced, pressure tested and valve guide seals replaced, new head gasket all new seals, etc. When we got the motor running it seemed to run fine but then noticed it had low oil pressure with the light coming on. I then got a gauge and hooked it up and at initial startup we get close to 65psi. After only about 10 minutes of running the pressure drops and drops until it is barely above 0 psi. I was reading it may be main and rod bearings - sure enough we dropped the pan and they were shot. Replaced all the bearings, fresh oil and filter started up and got the same results - 65psi at startup, after running the pressure drops to just barely above 0 psi. Was wondering if anyone had any experience with this and may know what we should check next? I keep leaning towards the oil pump but not sure that is the culprit. We shimmed the pump but that did not have any affect either.

 

did the machine shop do tear down and reassembly of the cylinder head?

there is an oil orifice in the head under the center cam cap on the intake side. if this wasn't reinstalled it could cause low pressure problems. i think it should have an o-ring too.

 

Hey hondamark35,

Thanks for that info - i will have to check and make sure it is there - along with the o-ring. Also, I just wanted to point out that my oil pressure readings are coming from the oil sensor location on the lower back side of the block just below the oil filter location.

 

98LudeJS,
You may want to verify that you are using the correct viscosity oil. Oil viscosity varies with heat. The higher viscosity of the oil during while the engine is cold is helping maintain the pressure. It is also possible that engine clearances are changing as the engine heats up. I would not expect clearances to increase to the point of no oil pressure, but its possible. One thing to consider when talking about oil pressure. The pump only produces oil flow volume. Restrictions due to bearing clearances, oil orifice, etc., is how pressure is produced.

 

It's actually right in the center under the center cam cap. But yes, this could contribute to it, though it won't be enough of a problem to cause near zero oil pressure.

 

did you mic or plastiguage the bearings/journals/seats? Or did you just slap new bearings in and call it a day?
If the previous bearings were shot, my guess is there is wear/damage to the crankshaft, causing much much larger clearances than it is supposed to have.
Also, there is a cylindrical o-ring in the crank girdle. Is it still there? and did you replace it? Any time the girdle comes off you need to replace that seal.
There's a gasket between the oil pickup and the oil pump too. That also needs to be replaced anytime the pickup is removed. Did you replace that?
If the previous bearings were destroyed, there would have been a lot of debris in the oil, and the pickup screen may have gotten clogged up. Did you make sure to clean that out really really well?