Car overheating above 3000rpm and oil pressure acting up

[brendanl96]

I have a 1990 300zx with 25,000 miles and my car has been over heating if I go anything above 3000rpm also sometimes my oil gauge will drop down to like 15psi when I'm idling. The car seems to have lost power since it's overheated and doesn't drive like it used to. I took it to a shop and they said I blew a head gasket and have warped heads and they said they did a die test but I'm not sure if it's my head gasket because I haven't really seen smoke come out of my exhaust.

Someone please help me and give me some advice.

[Ziggy1621]

Honestly, I would take it to a second shop for another opinion. And don't drive it except to the shop. You do not want to further any damage that may already be occurring.

Have you checked your water level? Color of the oil?

[brendanl96]

I havent checked the water but i did check the oil and it lookes fine

[IonZ32]

I havent checked the water but i did check the oil and it lookes fine

Check under the oil filler cap. My friends 87 supra blew a headgasket and the oil looked fine on the dipstick, however under the oil filler cap was the white paste seen when a car eats a headgasket. His didnt blow white smoke. He was definitely down on power as well. The oil pressure gauge stopped working due to it being clogged with that paste. So check under that cap and let us know if you find anything. A BHG isnt a hard job on a supra, I bet a Z would be a little more work though.

[brendanl96]

I looked and didn't see anything out of the normal looking at the engine and didn't see any white paste either

[IonZ32]

Hmmm, well if there isnt any water in the oil, maybe a broken water pump?
Check your radiator and water lines for leaks. And make sure its got plenty of fluid first though.

[t.mcginley.jr]

If your radiator is original, it could be clogged with debris just from age. You can check a head gasket by either letting it idle with the radiator cap off and see if there is a small, continuous stream of bubbles. You can also do a compression test. Low compression in specific cylinders, or two cylinders next to each other with the exact same compression usually indicates a busted head gasket. If it does turn out to be a head gasket, it generally costs a good amount of money for a shop to do mainly because of labor. Changing the gasket itself doesn't take alot of time, but getting to them is another story.

Are all of your vacuum hoses original? Lack of power can be caused by a vacuum leak, and vacuum lines will dry-rot with age.

As for the oil pressure, like someone said it could be the oil pressure sending unit. If its the original one, it's almost definitely busted. The original ones aren't very reliable and tend to give out after 10 years or so. New ones are like $35ish

[brendanl96]

Everythings pretty much all original since my car has 25,000 miles but ill check and do some tests and see how it goes.I was going to have a friend help me change the HG and pull the motor but i want to make sure thats the problem and its not anything else

[t.mcginley.jr]

Yeah do a compression test first and also check for continuous bubbling at the radiator while the car is idling.