OK what causes these to fail? as i think the thermos has failed again with in a month of replacing it.

 

the replacement was a genuine OEM part

Rust, silly temperatures on either end of the scale, manufacturing fault, incorrect/inverse fitting (Inverse doesn't seem possible on a Z, but is in some cars, especially old Ford Engines :rolleyes:), bits floating in your coolant (Metal filings etc.)

Rust, silly temperatures on either end of the scale, manufacturing fault, incorrect/inverse fitting (Inverse doesn't seem possible on a Z, but is in some cars, especially old Ford Engines :rolleyes:), bits floating in your coolant (Metal filings etc.)

 

Fitted correctly with the little wobbly pin at the 12 oclock position. cant say on stuff floating about in the coolent system, its failing to open again from what i can tell, top water pipe hot, bottom one and rad stone cold.

 

the last one failed to open correctly and upon examination, there was nothing that was stopping it.

 

could be heat though not sure why that would stop it working.

It's the same as anything else affected by heat mate, too much or too little can push the substance/material beyond it's limits and then it won't behave properly. Perhaps run a few rad flushes through it and just keep going until it starts working. Are you positive it's not the water pump that just isn't pumping the water? Or the radiator channels are not blocked up with silt? Or potentially an air lock in the system? Blockage in the heater matrix? Sorry haven't read your overheating thread, looked like you were getting plenty of help, so stayed out of it, lol.

water pump was changed about 3 weeks ago, a week after the thermostat was changed as i thought the same thing, lack of flow.

 

Radiator i believe is blocked anyway, but the nature of the thermostat is that it opens from the rear when the hot water heats the section inside the engine, thus allowing flow through the radiator. so it could actually be opening and the rad is just fecked now.

 

System was kind of flushed, but not with additives. although the water was rusty looking, there was no debris of any kind. closest ive come to seeing something like that, was with the rad cap on one occasion that had like a rusty clay substance around it, but haven't seen anything like that since then, that was about 2 months ago.

 

Getting to the point where im just going to say feck it with this zed. though, when Christmas and the first part of next year out the way, i might just get a jimmer rebuild on one of the 2 engines ive got in the garage and take this off the road till then and get the smaller issues sorted, and the manual gear box ready to go in.

Fair play mate. I'd disconnect the bottom pipe, then pour water through the top pipe (Note I didn't say through the rad cap) and see what the flow is like. If the flow seems slow, I'd say the channels are fubar'd. Get some rad flush, run it through, if the blockage isn't too bad, it'll stop overheating before you even drain the system again to get rid of the additive.

 

Another thing you can do, you say the top pipe is hot, the bottom is cold, how far down the radiator feels hot? In my previous experience, if the stat isn't opening, or is jammed slightly open and not opening all the way, the entire rad will get hot, whereas if it's a blockage in the rad, only part of it will get hot, the top part. In this case, the right hand end tank will probably still be cold too.

 

Remember, water is a good conductor, so even without flow, if there's no blockage in the rad, the heat will transfer through the water and the whole rad would heat up, if it's blocked though, only the section upto the blockage will heat up.

the whole rad is cold, yet the top pipe is hot ? does that make sence? yet there is water in the radiator. the pipes to and from the top hose are not blocked, and i can put water through the rad (well when it was off the car). the whole thing is just confusing as hell. and to be honest im getting to my wits end with the bloody thing.

That's weird as hell. Even without flow, the rad should ALL get hot if the top pipe does. Does the heater blow hot air once the engine is heated up?

i would say its got a radiator issue. havent you got another to try?

 

yeah but it leaks, was the reason i changed the rad. lol

 

heater blows hot air, but sometimes does go cold again until revs are raised, but i cant get any more water into the system. its full. think ill be checking all clips tomorrow and tightening them to make sure its not sucking air into the system when it cools down. but stuffed if i know whats going on with this rad business.

You can check the thermostat by putting it in a saucepan of water on the hob, heat it up and see if it opens at the correct temperature, that will either rule out the thermostat or show thats the problem, my first thought would be an air lock in the system as thermostats are pretty reliable and you have drained the system recently.

 

heater blows hot air, but sometimes does go cold again until revs are raised, but i cant get any more water into the system. its full.

 

That does normally suggest an air lock.

 

You can check the thermostat by putting it in a saucepan of water on the hob, heat it up and see if it opens at the correct temperature, that will either rule out the thermostat or show thats the problem, my first thought would be an air lock in the system as thermostats are pretty reliable and you have drained the system recently.

 

Agreed in 99% cases the thermostat fails open, air locks can be troublesome but not in anyway an unsolveable problem, loosing water then refilling then loosing water then refilling just keeps adding air as well trapped within the water.

 

Jeff TT

Went to top the rad up today thinking it might be low coolent level and that i was indeed loosing coolent somewhere, well rad was full and i couldn't get any more in if i tried.

 

But had a closer look at my rad cap, seems the rubber is disintegrating around the lower seal. this will most likely be where the system is loosing pressure and most likely sucking air back into the system when its shut off. Ive raised the car again, with the rad cap off and brought it up to temp, and also turned the heater on, i still cant get any more coolent in the system, the thermos is now opening again as the radiator and lower hose get hot (although the lower rad hose is substantially cooler than the top one, temp held at 83 degrees, even on a run to take my little one to school.

 

Hopefully a rad cap change will improve things and see where i go from there.

Hopefully a rad cap change will improve things and see where i go from there.

 

Its on its way:thumbup1:

Hopefully a rad cap change will improve things and see where i go from there.

 

Its on its way:thumbup1:

 

yay

 

Been driving it about today, seems fine again, its like sporadic lol and doing my bloody head in.

 

So glad its not a fast over heat, its gradual depending on driving style.

New rad cap arrived today from KJZ32 (mucho thanks) so took the zed out for a test run, went down the Duel carriageway temp held at 84 degrees, got her back home, and she started to creep up again till the electric fan kicked in at around 105 and she came back down and settled at 92, so still bloody hot. turned her off, think i have air leaking into the system at top inlet pipe for the heater matrix as i heard a bubbling sound from that pipe, also feeling the pipe you could feel it. so going to go tighten all the water pipes again to make sure.

 

still think the rad is playing a significant part as the top near the filler cap was stone cold again, yet the other side was nice and hot. so think i have a rad blockage.

 

Looks like the cars going to have to come off the road until new year when i can get some dosh to sort this out.

 

Gutted.

I still think you have air in the system, if its not loosing water at any of the pipes I doubt air is getting in there so you just need to get the air out thats already in there, I think you said about raising the car earlier in the thread so you already know to have the front end higher, if it was me I would drain the whole system, fill it up slowly whilst the front is raised, run the engine and if needed gently squeeze the pipes to help any air get out of the system.

I still think you have air in the system, if its not loosing water at any of the pipes I doubt air is getting in there so you just need to get the air out thats already in there, I think you said about raising the car earlier in the thread so you already know to have the front end higher, if it was me I would drain the whole system, fill it up slowly whilst the front is raised, run the engine and if needed gently squeeze the pipes to help any air get out of the system.

 

Thinking of digging the old rad out of the garage and sorting out the leak, as its leaking from one of the side joins and refitting it. this is starting to be a pain in the ass.

i still thinking your rad is fooked.

You need a steep incline (Nose up it) and to bleed the Air out...Can be a long process but think you've got air in there somewhere..

 

Run new water in with rad cap off and bleed screw open...(You can drain and put anti-freeze in when you know you have no leaks) rev to 2.5/3k and get as much water in as possible squeezing pipes etc. Once warm and your getting warm water in/through the rad, Close bleed screw, make sure that the rad cap end is full to the brim and rev again, whilst feeding in water, Replace cap, drop revs and take for a run...return to said hill again with Cold Car next day, remove rad cap and re-top up....Remember Fresh water contains oxygen! and compressing the water (*with Anti-freeze) raises it's boiling point, so temps on correct coolant might vary from Pure water...

 

Sure there's a 'how to' on here somewhere..

You need a steep incline (Nose up it) and to bleed the Air out...Can be a long process but think you've got air in there somewhere..

 

Run new water in with rad cap off and bleed screw open...(You can drain and put anti-freeze in when you know you have no leaks) rev to 2.5/3k and get as much water in as possible squeezing pipes etc. Once warm and your getting warm water in/through the rad, Close bleed screw, make sure that the rad cap end is full to the brim and rev again, whilst feeding in water, Replace cap, drop revs and take for a run...return to said hill again with Cold Car next day, remove rad cap and re-top up....Remember Fresh water contains oxygen! and compressing the water (*with Anti-freeze) raises it's boiling point, so temps on correct coolant might vary from Pure water...

 

Sure there's a 'how to' on here somewhere..

 

A much better explanation of what I was trying to say, not sure there is much point in doing all this and using a duff radiator, if you think this one is blocked and the other leaks probably best to either get a new one, second hand can get you out of a mess but is usually a false economy in the end.

Plus I really would not want to be driving a 300zx around with overheating problems, the stock temp guage is notoriously rubbish and the engine easily damaged.

Plus I really would not want to be driving a 300zx around with overheating problems, the stock temp guage is notoriously rubbish and the engine easily damaged.

 

Not using stock gauge, using conzults, as i said its not over heating rapidly, its a gradual over heat depending on how its driven.

just randomly throwing this out there, but just went to garage and tested something, went down the ring road to purposely cause it to over heat slightly on the way back, and parked with the nose up on the curb, now when it started to over heat the heating went cold. felt the water pipes feeding the heater and both were hot. radiator was stone cold again yet when trying to attempt to take the rad cap off, it wanted to spit hot water about so though better of it.

 

the moment the heating started getting hot again, the temp shot down from 100 to 81 degrees, (conzults software)

 

where the bloody hell is the temp being taken from for conzults? as it cant be the temp sender on the front water pipe surely.

 

Another thing, i have to raise the engine revs to cause it too cool down, though only when no load is being put on the engine (not driving). surely if it was a HG this would cause it to over heat more not less?

well that failed miserably, changed thermostat for a brand spankers one after washing out the system and getting as much crap as possible out, and its still over heating on idle. so i give up.

 

Most likely a small crack in the HG causing it now. only thing i can think of, even though no oil in the water or water in the oil.

 

:crying:

 

god the amount of work ive put into this bloody thing.

Edited December 4, 201114 yr by vodkashots

Do you know anyone that has a CO2 test kit that you fit on the radiator? Or take it to a garage that has one. If there is no oil in water and vice-versa its the only other possibility if its not losing water. Is your fan definately spinning fast enough? Belt/clutch not slipping?

im getting warm air out of the heater but no hot air, seems there is a major blockage somewhere, again getting the top hard pipe go hot, but bottom one stays freezing and its that brand new thermostat you dropped off last night. something just isnt right.

 

was just reading up on removing the heads, looks like im going to have to remove the cams as well to get to the head bolts but not sure due to the vagueness of the service manual.

 

though to be honest, i really dont have the room for such major engine work as i think the engine is going to have to come out of the car if i have to change the head gasket.

 

i cant even get it to a garage for a test as it over heats straight away.

 

The car has only ever overheated to 127degrees once. all other times its over heated i have shut the engine down before the temp go to 105c which is with in Nissan's tolerance range.

 

Ive been everywhere looking for leak test for the rad but no one seems to do a portable DIY kit?

 

May be my head isnt thinking right, but at the moment i really dont know what to do with the bloody thing, apart from torch it.