Oil pressure can read 40 pounds, rev the engine up
Oil pressure can read 80 pounds plus, also when first cranked the motor don't seem, by the noise of tapping, to have pressure and continues with noise too long. The engine shows full and is not dirty. The tapping noise concerns me because it sounds as if there is not enough oil pressure. Thanks
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Hi there: It sounds like it could be oil pressure sending unit. I would check the connection on the sending unit. Below are the procedures for checking the sending unit, If it checks out good I would have a mechanical gauge set up to measure the pressure.
TESTINGTo test the normally closed oil lamp circuit, disengage the locking connector and measure the resistance between the switch terminal (terminal for the wire to the warning lamp) and the metal housing. The ohmmeter should read 0 ohms.To test the sending unit, measure the resistance between the sending unit terminal and the metal housing. The ohmmeter should read an open circuit (infinite resistance).Start the engine.Once again, test each terminal against the metal housing:The oil switch terminal-to-housing circuit should read an open circuit if there is oil pressure present.The sending unit-to-housing circuit should read between 15-80 ohms, depending on the engine speed, oil temperature and oil viscosity.To test the oil pressure sender only, rev the engine and watch the ohms reading, which should fluctuate slightly (within the range of 15-80 ohms) as rpm increases.If the above results were not obtained, replace the sending unit/switch with a new one.
This may be due to the breather system being restricted. Have the system checked by a specialist as some systems are hard to diagnose.
It could be the engine is worn. If too much combustion pressure gets by the piston rings this will cause pressure to eject engine oil.
If the breather is fine then an engine leak down test is called for. This involves pressurising each cylinder and measuring how much air escapes. This involves using a Leak Down tool...consists of two pressure gauges and an air line and someone who knows how to use one.
A compression test will not tell you how worn your engine is. Compressions of 140 to 160 psi are possible even on a worn motor.
Leak Down readings should be below 12%...ideal would be 2% to 6%.... if higher than 20% it means you don't have an engine in there !
The oil sending unit is located on the engine block behind the drivers cylinder head area.You have to climb up on the motor to see it cause it is hard to see behind the wiring harness.You may also want to purchase a new sending unit because it is very long and you might need to buy the sending unit socket to replace it.Hope this helps.Good luck.
somewhere around 1.6 pounds (1lb.14ounces) of R134a if system is evacuated and 3 ounces of oil with new compressor. keep pressure on the low side around 34-37psi & it should blow snow. Below are normal car AC pressure readings with 134A.
Normal readings on high and low side with AC OFF (static pressure) – Depends on outside temperature, but normally is between 80-105 PSI
Normal low side reading with AC on high speed and MAX & engine at 800-1000 RPM’s – Ranges from 25-35 PSI –
Normal high side reading ranges from 200-350 PSI
Don’t assume that if adding little Freon is good that adding a lot is better! Overcharging just a little can decrease the performance of the system and possibly damage the compressor.
DIY recharge kit:
With the AC on the coldest setting, use a thermometer in a middle vent. Normal vent temperature readings will vary depending on the (ambient) outside temp. The vent temperature should range from around 42-55 degrees in my experience. If normal gauge readings are obtained and the vent air is cold – STOP don’t overcharge the system.
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Two things...when it reads zero, is there any engine noise (tapping or knocking)? After you rev the engine does the pressure read normal at idle and function normally, or does it go back down? Either way, you should not drive the vehicle 'till you have a mechanical gauge (yours is electro-mechanical) put on there and the actual pressure is tested. The condition may be a bad sending unit, a bad bearing or possible obstructed oil pump screen. The repair is obviously different for each one and the price is as well.
There may be a loose wire or the gauge or sending unit may be going bad. The first thing I would do is to hook up a temporary oil pressure gauge, not using the old one at all. With this watch gauge while driving and see what readings you get. If the readings still jump around you have a pump that is getting weak and failing, If that is the case the pump should be replaced, but with high milage you may consider rebuilding the entire engine. If the readings stay normal start checking for a loose wire at gauge or sender. Then check sender, then gauge and replace as needed.