Oil Pressure Question - Toyota

[Johnstra]

I just had a head replaced on my 6-cyl 1992 Toyota 4x4 truck because the cam froze (the guess is due to no oil). Runs fine now but as I drive it (say after 30 minutes or so), my oil pressure guage start dropping. It never goes all the way down but it gets close. My mechanic says he doesn't think it's a problem. If I restart the truck the pressure recovers.



What do ya'll think?

 

[B.G. Smith]

You need to verify if the oil pressure is really dropping or if the gage/sending unit is bad. From the cam failure I would be suspicious of low oil pressure. If the pressure comes back up by just shutting off and restarting, I would guess either a bad sending unit or a malfunctioning relief valve in the oil pump. If it comes back only when started cold and then drops after warming up, then it could be excessive bearing clearance in the rod/main bearings. bg

 

[Johnstra]

Thanks, BG. Suggestions for how to determine whether its the check valve of the sending unit? I'm tempted to just replace the sending unit and see if that resolves it.

 

[B.G. Smith]

You will need to remove the sending unit and install a mechanical gauge. If you don't have a gauge you can use it might be less expensive to do as you say and replace the sender. You cvan use just about any gauge, the thread where the sender fits is usually a 1/8 or 1/4 inch pipe thread. bg

 

[Got HO?]

Oil pump pickup.

If you verify a pressure drop with an external gauge, you need to drop the oil pan & check the pump screen for debris. Have had quite a few Japanese cars with this symptom in my shop. (Back when I worked on Japanese stuff) Sludge will get sucked into the screen & reduce oil flow. When you shut the engine down, some of it will drop back into the pan. usually see this on engines that have not been well maintained & are full of oily gritty deposits.