when hot z goes haywire

[300freekzx]

Ok when it cool out my car runs great but when temps get high the z goes fool! 1st coolant temp goes up (before you say I have drained and filled and burped the system so many times I am a pro at it) it never goes all the way to hot but damn near close. Crazy thing is I can turn the car off and if I am sitting idling it keep normal temp but as soon as I start driving it will go hot. Next when hot out it will idle high or irratic idle. Last my clutch is great when it is cool but when it gets hot loses pressure and starts to stick in and does not pop back. Tell me what ya think guys?

[Milton'Z Nissan'Z]

There are a couple of things to check when it's running hot. Aside from making sure all the air is out, which it seems you have done, there are really only a couple of other possibilities. 1 is the rad itself. Is it original or really old and never been professionally tanked and cleaned? The passages inside corrode over time and near block shut causing little flow to occur.
The second is have you ever pulled and checked between the rad and A/C condenser? Often over many years there ends up being a build up of crud from the road, leaves, particles etc which block the fins and in turn air flow. Also take a look at the front of the condenser to see if there is build up of junk.
Could be running weird when it's hot only because it's running too hot
Clutch hydraulic system sounds like it has air in it. When it gets hot, the air in the lines expands and can do some strange things. Could also be the master cyl on it's way out

[evildky]

being a professional when you burped the system you rememberd to have the heat on high...right?

if it's nto air then it's likely a clogged radiator

[300freekzx]

Thanks yes I had it on full blast. I will check the system do you think it could be the sensors on the hard pipe.

[DCaff300ZX]

One other thought...are you running on the original cats?
My '90 Z had much the same symptoms you describe before a new custom exhaust system went in, and the oveheating went away.
I also had earlier problems from a cracked inlet stem to the radiator that became known only when a repair shop broke it off fully during a water pump replacement/120K service, so check them both as well.

[300freekzx]

I still have the same exhaust on the car. I know the hard pipes are good

[300freekzx]

Ok went out and turned it on to check level. The I heard a weird straining noise while the car was warming up. The next weird thing is it took forever for the heater to come on. Once it did I let it run for twenty minutes put under mild load to watch the water move through the rad. I will tell you I have been fighting the rust situation in this car since I bought it and cannot get it out. Is there anything to clear out this rust? Next question does anyone have crystal clear pic of how the back water hoses after delete of hose under plenum on a N/A? I really appreciate it. If anyone has an insight on the sensors that are in the water hard water pipe as to whether they could make the z run go to the hot side. FYI the thermostat is good.

[evildky]

the senser and sensor i the hardpipes won't make your car run how, the single wire goes to your temp gauge, the one that looks like an injector clip goes to the ecu for cold start enrichments

if the car si running hot, it can only be 1 of a few items
air in the system, you cleared taht issue we think
lack fo flow, this could be a bad thermostat, bad waterpump, clogged headgasket coolant ports due to crappy addetives, if you say you ahve rust int he system it's most likely addetive and not rust
lack of cooling to the radiator, a bad fan clutch or a damaged fan can cause this, also a crappy electric fan taht can't keep up if somebonehead tried a elec conversion
clogged cat is a possibleissue but should come with noticible power loss form the time you start the engine

[stebo0728]

Quick question regarding the high heat when burping the system. Is this required if the heater core has been bypassed?

[evildky]

if the heatercore is bypassed there is a good chance you are sirculating the same hot water instead of the cool water form the radiator, a heatercore bypass should only be sone wiht a restrictor inline to limit flwo to keep it form recirculating that hot coolant

[stebo0728]

yes my bypass hose is kinked shut

[evildky]

not the answer I was looking for, a kink in a ruber hose is a potential leak and if no coolant gets pass it can be trapping an air pocket, so please don't kink your hose (kinda sounds dirty don't it?)

[stebo0728]

what is the proper procedure then? it was this way when I got it btw, and its down for the count till i rebuild the engine, which will include a new heater core, so the bypass will be deleted, but for others reference, and mine if i ever need to do it again, how to you do the bypass properly?

[evildky]

propper procedure is to fix the heatercore, but if you must bypass it put a restrictor inline and loop the hose so that there are no kinks