mysterious cooling problem with 79 280zx
 

First off I'd like to say this is my first time posting here and would really appreciate any help that can be offered. My Datsun has had ongoing cooling problems for over a year now and I am finally left without a clue as to what I should do, so here it goes.

My Datsun is a 79 non turbo 2+2 with an automatic transmission and I am only the second owner. The first owner replaced the radiator about 2 years ago before I bought it. When she did she mixed different coolants and created a muddy concoction in the cooling system.

It worked when I first bought it and I had some fun rebuilding the entire suspension, but I have since had ongoing cooling problems.

First it got a small leak in an auxiliary line so I replaced it, only to have the line going to the heater core through the fire wall bust and so I replaced that.

Then it started overheating immediately after it warmed up, so I replaced the thermostat, that didn't work, so I replaced the radiator cap.

Then that didn't work I realized the clutch fan wasn't working, so I replaced that.

After that, coolant would shoot out of the reservoir cap and deplete the radiator, so I did a few tests.

I did a pressure test to find that there was indeed a leak. I took the spark plugs out and inspected them and they were fine. There was no water coming out of the spark plug holes when I turned the engine over so I assumed it wasn't the head gasket.

With that done I assumed since I didn't see a leak that it was the water pump. So I replaced that and since I suspected a block in the radiator from the sludge of mixed radiator fluids, I replace the radiator too.

The problem still persists, and the only thing I can think of is that there is a block possibly in the engine itself from the sludge and I have to take it all apart. If any one has any suggestions please let me know! I appreciate everyone for taking time to think this through with me.

Also, what is the inlet looking thing below the power steering reservoir that goes from the heater core lines into the block?

Thanks guys

Welcome to ZDriver! :023:

Water doesn't have to shoot out of the spark plug hole for the head gasket to be blown. It's actually pretty rare it get that to happen (more likely when you drive your car into a lake). :D

You should read my "head gasket denial" thread: https://www.zdriver.com/forums/other-cars-223/damn-freaking-metro-29223/

In a nut shell, my car BARELY overheated, and after that it would puke out coolant when the thermostat opened. BLOWN HEAD GASKET.


Inlet looking thing? As in the "water pump inlet" ???

Sorry, I forgot to mention that I ran a compression test on the cylinders and all the cylinders had great pressure. Also, I don't know that it makes a difference but with no smoke, no oil in the coolant, no coolant in the oil, and perfect looking spark plugs, I ruled out head gasket.

Did you read that thread I posted?

I did after I replied, and your probably right. That said, I really want another way out. Could there be any other possible explanation?

You already covered everything. theres only 2 options left. Blown headgasket (its really not that hard to change!) Or entirely clogged head/block.

And if its the engine block thats clogged some good coolant flush "Might" clean every last drop of the gunk out.

Alright guys, Thanks. I just have to face the head gasket truth. Would you guys recommend getting the block/cylinder head machined down a bit?

The block should be fine. but I'd take the head in and get it rebuilt. Shave the head down only as far as it needs to go to be level again. Thats it. else you will have to start shimming up the cam towers and lots of other headaches.

Alright, thanks. I was mostly worried about the block being warped and needing to take the whole engine out.

The block is iron... it doesn't warp. Only the aluminum head would warp, and the machine shop will check it all for ya. :D

OH, of course! that makes perfect sense. I didn't do my homework and assumed that both the block and head were cast iron. Thanks man

That's the bad part about these engines. The blocks themselves are tough as nails. It is the heads that are weak. Because when you put aluminum on cast iron. You run into problems. But as long as your head is straight, torqued down right. And you watch your coolant, and have a working temperature gauge. It will last you a long time. Take it from me, do not let the gauge sweep all the way over. And continue to run the car. You will warp, and or crack the head. Been there done that, 3 times now. Good luck

I've seen cast iron L engine heads before. and I think they weigh more then the block does lol so They didnt really have a choice. Way to heavy or a slightly weaker head.