Suspect water pump

SouthArk370Z

Sounds like it may have been run without antifreeze.

You may have some of the same scaling on the pump impeller fins and/or water passages, reducing pump output and flow through the system.

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Z_ealot

That was my thinking right there too, i ran a bottle of the prestone super flush cleaner through the system for a few days before i swapped out the radiator and did get a pretty good chunk of white powdery stuff that ended up inthe overflow reservoir if that tells you anything

SouthArk370Z

That chunk may have been part of the impeller. I'd plan on replacing the pump and doing a very close inspection of the entire cooling system. If the corrosion is bad enough to eat the impeller, no telling what other damage has been done and what has been plugged up.

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Z_ealot

The whole reason i swapped out the radiator was that i was having the exact problem im having now with the system only overheating at idle with the ac on. You think running some more cleaner through the system would help or should i plan on replacing the water pump and then run cleaner through it afterward?

Dreadnaught

This. Sounds like it's also due to poor maintenance by the previous owner like the OP stated.

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Spooler

If your issue is only at idle you need to look at the radiator fans. Make sure they are kicking up to high speed at idle and they are both working. You could test these with Nissans Consult. Not sure how you would do it without the Consult tool. Uprev or Ecutek may be able to do it.

I am going to ask a silly question. Did you remove the bleed screw out of the radiator when filling with antifreeze?

SouthArk370Z

Definitely worth checking before taking more drastic measures.

A non-contact tachometer will tell how fast the fans are spinning (may be able to borrow one at a parts store). Not sure how fast they are supposed to turn but that info may be in FSM. Or compare to another Z.

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Z_ealot

Have checked this multiple times and both kick on high speed when the coolant temp hits about 214

Spooler

Sounds like you are done and need to take it to someone with more knowledge than you. Just sayin.

Z_ealot

Took it to a shop, they are the ones that suggested to swap the radiator and if that didnt work they suggested to do the water pump next

SouthArk370Z

They should be able to check the radiator before deciding whether or not to replace. Same with the pump.

If the radiator is plugged with sludge, the block probably has some sludge buildup too.

I'm still not 100% sure that corrosion/sludge is the problem (although it sounds like the top candidate). If it were me, I'd inspect the radiator and pump before I started replacing parts. I'd do whichever was easiest first. You should be able to get a good idea of radiator condition by pulling the inlet hose and using your borescope.

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Z_ealot

Radiator is an almost brand new unit though that i swapped in

SouthArk370Z

Until you do some investigating, who knows what the real problems is? Check for corrosion and sludge before you start swapping parts.

If corrosion is not the problem, check for flow. FSM may have a procedure.

I'd also double-check fan speed. I doubt that they are the problem but one may not be getting up to speed.

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SouthArk370Z

The two basic problems that I've run into with air/liquid heat exchangers both have to do with flow - either the air or the liquid is moving too slow (too fast is also a possibility, but not very common and certainly not your problem).

You seem to have good air flow (although your testing methods are not very reliable). Low flow is usually caused by a bad pump or blockage (stuck 'stat, something in a passage, heat exchanger pluggage, etc).

You've checked all the easy stuff. Go ahead and pull the pump for inspection. Use your borescope on the block while you have things apart.

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Z_ealot

I realize my hand is not a very reliable way of testing, but it's what I have access to lol. I don't have access to the tool to set the crankshaft in place to loosen the crankshaft pulley so looks like I will be saving up for a little bit before I can have the shop inspect the water pump for me. gonna drain the system this weekend in the interim and take a look around with my borescope and try to get pictures for those interested.