24 minutes ago, chaseincats said:

A few things:

• Notes:

• check your oil level. at idle mine will sit maybe twice as high, but not that much higher. when you're driving, it should zip up to half+

• Tests: if air isn't your issue then let's talk about the other ones

• Thermostat - since you already have yours out, lets test it. throw it in a pot of water on your stove and use a thermometer to see if it FULLY opens at 75c (use a meat thermometer or something in there to see when the water is the right temp). if not, your thermostat isn't allowing all of your coolant to cycle and that is the issue. I did this a while ago when i suspected my thermostat and that proved it was the issue. the thermostat keeps the car at a minimum temp, not a max one. if you remove the thermostat, it will get to 3/4 still...but it will just take longer if the thermostat is functioning properly

• Radiator: do you have enough coolant in it?

• Temp gauge: use an IR temp gun to see what temp your engine really is. I wonder if your temperature sending unit is just wrong. shoot the IR light on the temp sender plug area

Car is running 10w 30 synthetic oil. Should i replace oil to 20w 50? Or is this irrelevant. Also whats the risk of running the engine with no thermostat? Need to lower that temp.

3 minutes ago, 72 Datsun 240z said:

Car is running 10w 30 synthetic oil. Should i replace oil to 20w 50? Or is this irrelevant. Also whats the risk of running the engine with no thermostat? Need to lower that temp.

run it with whatever oil datsun recommends (I dont remember). Did you pull the dipstick to see if the oil level is low?

running it without a thermostat can be detrimental in that there isn't a thermostat there to slow the SPEED of the coolant. meaning the coolant can be pressurized more than components are designed to hold. also, if the thermostat you have is working properly, then removing it (besides causing harm) will just be a waste of time. since you already have the thermostat out of the car, just throw it in a pot of hot water and see if that is your problem. all of those tests i wrote out literally take less than 10 minutes

3 hours ago, chaseincats said:

run it with whatever oil datsun recommends (I dont remember). Did you pull the dipstick to see if the oil level is low?

running it without a thermostat can be detrimental in that there isn't a thermostat there to slow the SPEED of the coolant. meaning the coolant can be pressurized more than components are designed to hold. also, if the thermostat you have is working properly, then removing it (besides causing harm) will just be a waste of time. since you already have the thermostat out of the car, just throw it in a pot of hot water and see if that is your problem. all of those tests i wrote out literally take less than 10 minutes

Dip stick out and the car was running with no thermostat. This is really weird. Any solution before opening the engine?

1 hour ago, 72 Datsun 240z said:

Dip stick out and the car was running with no thermostat. This is really weird. Any solution before opening the engine?

Hang on - the engine runs with the thermostat cover off and the coolant doesn't go all over the garage? If that's the case there is something dreadfully wrong with your water pump.

The car running with the dipstick out is an unrelated issue. If the car runs fine with the dipstick out it means the car has a pretty large vacuum leak that a previous owner didn't find/look for and instead tuned the idle speed to compensate.

Also that oil on the dipstick looks pretty terrible - I'd strongly consider doing an oil change asap

Way way past an oil change and low on oil. Going down a rabbit hole here. A good tech would have seen if there was circulation through the radiator. Posting non conclusive results.

Should i change the motor oil to 20w 50? 5 quarts?

4 minutes ago, 72 Datsun 240z said:

Should i change the motor oil to 20w 50? 5 quarts?

this is the oil you want

2 hours ago, chaseincats said:

Hang on - the engine runs with the thermostat cover off and the coolant doesn't go all over the garage? If that's the case there is something dreadfully wrong with your water pump.

The car running with the dipstick out is an unrelated issue. If the car runs fine with the dipstick out it means the car has a pretty large vacuum leak that a previous owner didn't find/look for and instead tuned the idle speed to compensate.

Also that oil on the dipstick looks pretty terrible - I'd strongly consider doing an oil change asap

You misunderstood me. I opened the thermostat housing and discover the tech had not replaced the mishimoto 75 degreees thermostat. Im testing the car tomorrow, adding 1 quart of 10w 30 synthetic oil and reverting. Im concerned about the temperature. How come it goes to 3/4 with no thermostat??

3 minutes ago, 72 Datsun 240z said:

You misunderstood me. I opened the thermostat housing and discover the tech had not replaced the mishimoto 75 degreees thermostat. Im testing the car tomorrow, adding 1 quart of 10w 30 synthetic oil and reverting. Im concerned about the temperature. How come it goes to 3/4 with no thermostat??

Ok, so just to confirm - the car is now driving without a thermostat and you are getting the same 3/4 on the temp gauge that you got when the thermostat was installed in the past, correct?

It that is the case, then the thermostat theory is out the door. Turn the car on with the radiator cap off and look to see if the coolant is circulating since the thermostat is off the car. Then press the throttle linkage to rev the engine and see if the coolant speeds up everytime you rev it. That will tell us if your water pump is working. Also, you'll know if you're low on coolant.

Edited April 23Apr 23 by chaseincats

I drove the car from the mechanic shop to my house with no thermostat inside the housing. During light traffic i got to 3/4 temperature. Something is just not correct.

There’s no misunderstanding on our end. You are not clear on the logistics of what’s been done on the engine itself for a very long time. You may have a bad gauge. Others have mentioned to use a temp gun. You’re negating what we suggest. Looking for a quick fix and there is absolutely no such thing. My 2 cents

I paid a Camaro mechanic to solve this issue and he has done all possible external tests. Unfortunately, heat problem is still there. He did noticed 2 things:

1. Oil pressure very low. It only rises when you accelerate.

2. Cylinder 4th could have a problem as measurement are not within 10 percent.

Ill do the radiator test tomorrow. How long shall i run the engine at idle withe the cap off?