71 240z strange overheating/cooling system problem.

[tzagi1]

Background: the car has been driving great back in the mid to late 90's, been parked in a dry enclosed space (socal) from 97-8 till now.
since it was pulled out of storage (last year) the radiator (aluminium job, 3 row, much bigger then stock) been replaced, water pump been replaced, new thermostat been replaced.all hoses been replaced.
What can go wrong?
well.... it acted as if the thermostat(180f) will not open, the gauge pegs and the bottom hose is cold, replace thermostat..same thing, cut up the old thermostat(as in remove the wax pellet) and try again, much better but now it heats at streetlights, cools off while driving, remove the 2 12 inch electric fans and reinstall the mechanical. retest, but now it's after 4pm (the sun is setting and the temp dropped by 10 degrees)
so far could not get the gauge to go over half.....will be trying again tomorrow, still noticed a big difference in temp between the upper and lower hoses.
Ideas?

Update, took the car for a "long" (20 miles drive aprox) once warmed up the gauge stayed at half while driving HOWEVER it climbs quickly at every red light, if I am to raise the rpm over 2000 while standing it brings the needle back down. if I get the car to speed and then coast at idle...same thing, the needle climbs, I'm suspecting that its not air flow but rather water flow as if there is a restriction in the system,  still have a boiling hot upper hose and a luke warm bottom hose.

[Patcon]

Maybe you need to flush the block. Was it stored with antifreeze in it or water? Maybe the jackets are all scaled up...

[tzagi1]

When I got to it and drained the system out came about 2 quarts of rusty water...I would say that the vast majority has evaporated over the years. even with rust in the jackets it doesn't explain the flow issue.

[Mark Maras]

 i agree with Patcon. Time to flush the cooling system. Many members have reported large quantities of scale in the block when the expansion plugs have been removed. Hope yours cleans up with a good flush.

 

[Captain Obvious]

Maybe there's a rag stuffed into the radiator connector nipple where the hose connects.

[tzagi1]

While the flushing is certainly a good idea,,,,its not in line with the symptom, it does not explain why it requires 2000 rpm to have flow in the system nor the restriction.

Cap, that's what it acts like...except everything is new and no rags present. 

I'm thinking to fill it with vinegar or I might have a flush kit from the 90's...that was some strong stuff..

[Mark Maras]

 I wonder if anyone has ever filled one with CLR and let it set for a few days? It works wonders on other metal parts.

[Mikes Z car]

  I guess this might be a long shot but I wonder if the impeller blades could be rusted off badly.  I remember seeing a water pump from a 240Z where large portions the impeller blades were rusted off so not much of the impeller was left which must have really reduced water flow.  Can't remember if I saw that on a water pump from my car or if it was a pump someone else had or if I saw it on a website.  If I recall the water flow from the water pump can be seen with the radiator cap removed?  Not sure how one would quantify what a sufficient flow would be.

[Mark Maras]

 I considered a bad pump too but it was replaced. How about something far simpler. A bad, new thermostat. I'd try removing it and put it in boiling water to see if responds and at what temp.

[David F]

Since water pump, rad, thermo are new then I would flush the heck out of the block (backwards, of course).  Ensure you get a good flow form everywhere.   Take the pump off and flush with hose nozzle directly into the block (both directions).  Don't forget the heater core.  And, I would flush the rad as you may have introduced scale into the radiator.

[Captain Obvious]

Sorry... I said rag. I meant cork. I know it's a new radiator:

http://www.classiczcars.com/topic/58783-overheating-after-modifications-what-am-i-overlooking/

[tzagi1]

Update:

Did the flush, first back flushed it (using the $4 kit) bypassing the heater core (brand new), flushed until water runs clear, drain radiator, refill with a 50/50 mixture of muriatic acid and water total 1 gallon.

Start up till warmed up, cool then drain, what came out is darker than coke! completry black., keep back flushing till water runs clear, now refill with a mixture of baking soda and water to neutralize the acid. I left the cap off and started, immediately water started to pour out, at that point I installed a rad pressure tester, immediately the pressure rose fast...so I shut her off.

Conclusions: Its either I have a completely clogged radiator, yes it's new but strangest thing have happened OR I have a blown head gasket.

I think I'll start with the radiator...sounds easier.