well its been 30mins since i did the block test kit and guess what?

 

 

it stayed blue

 

this is the kit i got

 

http://www.uktools.com/block-tester-p-12508.html

 

Tests in seconds for:

Cracked Blocks

Leaky Gaskets

Cracked Heads

Warped Heads

When Fluid Turns From BLUE TO YELLOW Combustion Leak is Present.

 

well its still blue...

 

so what on earth is causing my overheating issue.

 

The car has only ever reached 127degrees once. all my testing I've never let the car get higher than 105 as I've shut the engine down once it approaches 100c

 

So im now stumped

 

But im glad its not a blown head gasket.

its been an hour now and its still blue.... just had a lengthy talk with JeffTT as well and we are both stumped. so any suggestions more than welcome

 

so far changed the thermostat, radiator, water pump, replaced both pipes on the plenum bypass. flushed it out no end of times

 

Before rad change i could drive it around under 50, go over 50 it would gradually over heat.

 

after rad change, it worked flawlessly for 2 hours, even on boost. parked it up for the night, went to it the next day, and it started overheating on idle. (again gradually not fast)

Sorry dude, but put another rad in it, you've got another circulation issue. You need to get to a mates who has a hose and blast the thing out as someone else suggested earlier, then put a known working, clean radiator on it. There isn't THAT much that can go wrong and cause this, blockages, air leaks in the water system, blown head gasket, thermostat and water pump. Unless your new water pump (I'm assuming this was NEW and not second hand?) has broken immediately, it's not that, your thermostat is bloody unlikely to have locked again, although if it hit 127 degrees, it is possible, but in which case, it would most likely have locked open not shut, so it isn't that, air leak/lock is quite possible, although if you've bled it and bled it, probably not, did you say you did the test of unhooking the heater pipe, running it and filling it up until it came out of that pipe? I reckon either a/some water galleys are blocked, or you have a blocked rad again.

it reached 127 degrees the very first time it over heated, that was due to a thermostat failing to open fully, since then its had 2 thermostats, brand new water pump, rad change blah blah, really getting fecking annoyed with it, but at least i know its not a new engine .

yeah definitely good news there, but bizzare matters at hand still. I reckon get it to a mates with a hose pipe and blast it out, even if you have to pull over every 5 minutes till you get there. Pick a close friend!

What is you ignition timing like?

Incorrect settings can lead to excessive heating issues.

What is you ignition timing like?

Incorrect settings can lead to excessive heating issues.

 

15 degrees btdc, did it with a timing light on the crank pulley and also used conzults to double check cas is sitting about half way.

ive changed the rad cap as well, just thought id let you all know before someone suggests it, and the fan clutch

Did you turn the heater on after you filled the new rad? could have an air pocket in the heater core.

ive changed the rad cap as well, just thought id let you all know before someone suggests it, and the fan clutch

 

Are there any mods you did prior to the problem first occuring? ie dialled up the boost a bit, chipped the ecu etc etc within 6 months prior to the problem first starting.

Also, is it actually using any water or is it just overheating? if so how much water is it consuming?

could it be a electrical problem if youv eliminated mechanical proplems

could it be a electrical problem if youv eliminated mechanical proplems

 

The whole cooling system is mechanical with the viscous clutch fan on the front, The electric fan wont kick in until much later, so for it to climb up in the first place does show a cooling system issue.

 

While we are on the topic i will add a bit i learnt while doing my full rewire.

 

I looked into the differences between the TT and n/a electric fans as i have one of each, and the TT has an extra wire run to it, which upon research is because it is a dual speed fan, alot of people it seems believe the electric fan is only for a/c usage, this is simply not the case...

 

People also do TT swaps and don't bother putting in the 2 speed fan and can run into problems in traffic etc, but as i say i don't think its overly relevant in this case, but worth a mention none the less.

 

Below are the electric fan parameters:

 

The NA Z32 has a single speed auxiliary fan. The following specs are for the NA fan, and come from the Nissan service manual. Temps are in Fahrenheit:

 

A/C off, coolant temp below 219 = fan off

A/C off, coolant temp above 221 = fan on

A/C on, vehicle speed

A/C on, vehicle speed

A/C on, vehicle speed > 25mph, coolant below 219 = fan off

A/C on, vehicle speed > 25mph, coolant above 221 = fan on

 

The TT Z32 has a two speed fan. The following specs are for the TT fan, and also come from the Nissan service manual with temps in Fahrenheit:

 

A/C off, coolant temp below 219 = fan off

A/C off, coolant temp above 221 = fan on

A/C on, vehicle speed

A/C on, vehicle speed

A/C on, vehicle speed > 25mph, coolant below 219 = fan off

A/C on, vehicle speed > 25mph, coolant above 221 = fan on

 

As you can see, the fan is ECU controlled (A/C, temp & speed sensor input feeds to ECU, output from ECU for fan operation). It is also obvious the fan should not run very often if the cooling system is operating efficiently.

 

The full write up is here... http://www.twinturbo.net/nissan/300zx/tech/auxfan/auxfan.html

Also, is it actually using any water or is it just overheating? if so how much water is it consuming?

 

ive covered all this in my other threads but heres the run down.

 

Got the car in may with engine and gearbox issues.

 

Engine came out in august and parts swapped over from old engine to new (plenum, polished water pipes, polished cas, new PCV valves and rubber)

 

while the engine was out, water bypass was done, oil filter changed, oil pressure sender was changed for after market one.

 

Cam covers came off to check cam belt but its new so was no reason to change it.

 

engine went in the car and the car ran fine for 2 months with no issues apart from what seemed to be safemode, had a bit of a airpocket in one of the water bypass pipes but that was cleared once the pipe split and got replaced for a better grade one, passenger side turbo pipe also failed not long after so that also got replaced for better grade coolant hose (original bypass hose was what steams gave me, ive advised him to change his as well)

 

Car still ran fine, took car over a friends house which is 22 miles away from me, temp was fine all the way over until i parked on his drive with my nose facing down and the temp shot up to 127.

 

Car was turned off instantly, at the time the car overheated, car was running stock ECU as id removed my chipped one and the timing had been set accordingly, only mods were FMIC, fully decatted exhaust, and performance airfilter, boost was stock.

 

I then got the car trailered home, next day i filled the system up got it to temp and checked the rad hoses, top one hot bottom one freezing. whiped out the thermostat and tested it, it opened all of 1mm even in boiling water.

 

Dug old but working thermostat out of garage tested it before i put it in, gave engine a flush through, put the system back together, it carried on overheating only when driven at above 50mph.

 

I then changed water pump and fan clutch, and it carried on doing the same thing, so i took out the stock ECU, replaced with Socketted and chipped ECU, redid timing as it was 30 degrees out, car then sounded a lot smoother, it still over heated as before yet took longer to get there.

 

Next up was the rad change, changed the radiator for a none clogged one, took the car out for a good 2 hour drive including boosting and driving of 70mph, got home and let the car idle, hottest temp that was read during that time was 87 degrees C, thinking the problem had been delt with, car then was shut off for the night.

 

Next day i started her up, noticed i didnt have any heating, turned on the carputer and started conzults, engine temp was creeping again above 90 so turned the ignition off, got a brand spanking new thermostat thinking that it had failed, replaced the thermostat and also flushed the engine again, checked old thermostat but it was fine even opening at the correct temperature and opening to the full 10mm, i also replaced the rad cap twice just incase, still she over heats on idle and thats how shes been since. overheating gradually on idle and hasnt moved from her parking spot.

 

She does not loose coolant as i can not get any more into the system, ive tried various things with no success, in a way i was hoping it would fail the block test as at least then i knew where i stood, but as its passed, im back to square one.

 

Ive changed almost everything to do with the cooling system, even going as far as to remove my silicone lower radiator pipe to put it back to stock and its still doing.

 

She has new thermostat, new water pump, replaced ecu, replaced rad cap, replaced rad, replaced water bypass pipes, replaced lower rad pipe (cant replace top ones as they are modified to have my after market temp gauge on, but they are in very good condition (the rubber ones not the hardpipes)

 

I have no leaks anywhere, my heater matrix isn't leaking, as i said im not loosing coolant. i have no mayo in the engine oil, and no mayo in the radiator.

 

As far as im concerned ive changed just about everything i can apart from the engine and the heater matrix, the rubber pipes i haven't changed have been inspected for defects and none are showing.

 

My mrs dad is coming over tomorrow with air compressor and we are going to pressurise the system to 15psi and see if there is a leak.

ok what i was getting at was maybe the temp sensor is sendind wrong signals

i had this when i was getting overheating issues wasnt turnd out it ws a faulty sensor telling m it was overheatin when it wasnt

ooh, and the cooling fan on or off makes no difference, so might be back at a clogged radiator lol

ok what i was getting at was maybe the temp sensor is sendind wrong signals

i had this when i was getting overheating issues wasnt turnd out it ws a faulty sensor telling m it was overheatin when it wasnt

 

Covered that with jeff, its definitely over heating matey, i have 2 separate temp sensors and conzults which is why i asked where conzults was taking its temp reading from.

 

no only that, it tries to push cool coolant from the rad out into the overflow, which suggests to me its a airlock still, as the air is expanding and pushing the water out via the overflow with out the coolant being hot enough too.

 

Just seems strange though, would of though id of managed to shift an airlock by now with the amount of times the engines been stripped.

is it an N/a ian

Thanks for that, perhaps merge all the threads on it...

 

It seems you have covered all the bases really, the only coolant system problems i can see that would still remain would be an air pocket in the heater matrix, or a blockage in the water galleries. of the turbo(s) or the block.

 

Component wise you are well set with all the new parts so i suspect it is more of a flow issue. At least you've taken the effort to narrow it down.

 

We can all throw ideas, most will be wrong, but better to check it out than overlook it. Once the old man is vertical i'll see what his input on it is.

is it an N/a ian

 

UK twinturbo bud. engine had a rebuild back in 2007 going by zerocooldels posts as i got the engine off him, it then did 7k miles on the rebuild before being took off the road for over a year. not sure why though, think it was body work related.

 

I then bought it, changed all my shiney crap over on it and plonked it in. was running sweet as a nut after id changed me gearbox fuse.

scrap that last post

that s a head scratcher to replace nearly every cooling componant and still have issues

what about going back bofore doing the water bypass

Blockage in the system somewhere? A thought as mentioned hook the rad upto a hose pipe and see what runs out the bottom? Maybe then disconnecct heater pipes and do the same through heater matrix, then is there a way to do the same with the engine- in through bottom hose, connect two heater hoses together, take thermostat out and then see what comes out the top hose??

 

Might tell you where a blockage could be?

maybe a long shot but could faulty intercooler cause overheating

Covered that with jeff, its definitely over heating matey, i have 2 separate temp sensors and conzults which is why i asked where conzults was taking its temp reading from.

 

no only that, it tries to push cool coolant from the rad out into the overflow, which suggests to me its a airlock still, as the air is expanding and pushing the water out via the overflow with out the coolant being hot enough too.

 

Just seems strange though, would of though id of managed to shift an airlock by now with the amount of times the engines been stripped.

 

http://www.ehow.com/how_5164960_change-engine-coolant-nissan-zx.html

 

Points of note being turning the heater on and rad cap off while it bleeds, actually just go through the whole thing... :tongue_smilie:

 

300zx's are a pain to bleed but once its done right following that procedure you can rule out any air lock.

Blockage in the system somewhere? A thought as mentioned hook the rad upto a hose pipe and see what runs out the bottom? Maybe then disconnecct heater pipes and do the same through heater matrix, then is there a way to do the same with the engine- in through bottom hose, connect two heater hoses together, take thermostat out and then see what comes out the top hose??

 

Might tell you where a blockage could be?

 

last time i had the front apart to replace the thermostat, rad still looked very rusty with the water coming out, but the engine was clear as day when i ran water through that with out the thermostat on.

 

Looks like getting a uprated radiator might be my next step followed by a heater matrix bypass just to eliminate that from the equation, if my main rad was blocked like it was before i changed it, i doubt the heater matrix has fared very well given its smaller with smaller galleys to run water through.

http://www.ehow.com/how_5164960_change-engine-coolant-nissan-zx.html

 

Points of note being turning the heater on and rad cap off while it bleeds, actually just go through the whole thing... :tongue_smilie:

 

300zx's are a pain to bleed but once its done right following that procedure you can rule out any air lock.

 

ive had 5 300zx's, this isnt the first one ive done a coolant change on lol, or changed the water pump or thermostat for that matter.

 

Last zed never had any of these issues after id changed water pump and thermostat.