Anyone have any ideas on this one...

 

temp sensor shows just below 50% temp which is my normal... but when I boot it and spin up turbos, the sensor going down to nearly 0% and flickers

all over the place down there..... stop booting it and after 20 secs or so

it settles at below 50% again.

 

My first thoughts were that I had a water leak again, and that there was enuf water to cover the sensor just about, but when the engine was pushed (more water over turbos ?) the temp sensor was finding itself in air, leading

to *****cks reading.. flickering due to intermittent water contact ?

 

However, now engine is cool, I have taken rad cap off and it's full to brim.

 

Header tank is ok too, though to be honest I've never trusted that thing as I have twice in the past overheated because of a water leak and it didn't suck any water in from header tank for some reason (and I've checked the pipes are free of blockages, etc).

 

So.. is it possible that the rad would look full, but there is still a air in the

system just making it look full when it is in fact not ? How can I check there

is no air ? I was thinking of taking the top pipe off the rad on left hand (facing engine). I squeeze this and the rad level goes up as you would expect... but then it would do this if it was full of air too... so I'm assuming that if I take this pipe off and it's full of water we are ok. If not, there was some sort of air block for some reason....

 

Any ideas welcome... having overheated twice before (once due to burst water pipe.. once due to water pump dieing and leaking everywhere) and really don't want to risk it again :-(

 

stu

Are you sure the sensor is working ok, have you done an ECU diagnostic?

sounds more like dodgy wiring to the sensor, get someone to wiggle the connector harness at see if it affects the reading, theres 2 on the outlet pipe, left side is ecu sender right side is dash sender, looking from front

hth

ok will do.

 

I've had trouble with the ECU sensor before, but that's obvious as it sticks it in safety boost which I usually recognise immediately (where have all the horses gone!, etc). Saying that I have been driving my mundaneo recently so probably even a safety boost 300zx would feel quick.

 

does grounding the dash sensor make it go to zero or 100%...and I'll try that.

 

still... you'd think if it was that, it would do it all the time and not have anything to do with how hard I boot it.

 

Was also thinking of loosening dash sensor and seeing if squeezing left rad pipe releases any water (or just air) as this is about the highest point in the system isn't it ?

 

stu

ok.. dash temp sensor seems ok

 

I definately don't think there is water in the upper pipe.

 

I think my water pump may be buggered....

 

With engine running, I took radiator cap off... water is just sitting there in there... shouldn't there be obvious activity...if not water spurting out when I do this, at least turbulance ?

 

The water pump does run all the time doesn't it (off accesory belt).

 

If this sounds like the water pump.. could it be the impellors have fallen off it or something ? Thing is, it was replaced in 99, so you'd think it would be ok...

 

stu

Stu

 

...water pump bearing seals pack up and you loose the water or the shaft breaks and the belts flap about. I'd say it's an electrical connection. You've left it sitting in the garage too long...

 

good luck

 

Jack

 

...going to Woodbridge on Sunday?

hmm. ok leccy connection.. but I just ran it for 10 mins to get it up to

temp, and the water in top left hose into rad is clearly hot, and hot left side of radiator, but the right side of radiator and the bottom hose coming out of rad on right is still cold... efficent as a radiator is, I'd expect once it had reached temperature and opened the cooling system to the readiator that the water out the bottom of radiator would be obviously warm too..

 

and taking the lid of the radiator still just shows the water just sitting there... as if there was no flow of water through the radiator at all.

 

p.s. by this time the dash temp sensor is showing normal temp and working fine (car stationary).

 

Just seems weird... and don't want to take any chances..

 

what's happening in woodbridge on sunday jack ? (will be sailing round the canaries anyway.. but would be good to know what I'm missing :-) )

 

stu

...thermostat not opening?

 

Sunday at the airstrip - there's something called top speed challenge? - setting up a drag strip, £10 to spectate £30 to take part (has to be pre-paid) and a burger van so I'm told...

 

I'm sure you'd be there but hey, sailing round the Canaries hast to take prescedent.

yup. reckon you could be right. left it on for 15 minutes, and bottom rad pipe is still cold. I reckon the thermostat is closed and not opening.

 

You'd think the temp sensor would show temp going up right enough, but maybe it takes longer or something. both sensors are definately working fine (taking ECU one out makes engine go into mental mode, taking dash one out makes gauge go to zero).

 

Bugger. As you say... too much leting it sit in the garage.

 

stu

...Bramford Motor Engineering whilst you are on holiday?

yup. reckon you could be right. left it on for 15 minutes, and bottom rad pipe is still cold. I reckon the thermostat is closed and not opening.

 

You'd think the temp sensor would show temp going up right enough, but maybe it takes longer or something. both sensors are definately working fine (taking ECU one out makes engine go into mental mode, taking dash one out makes gauge go to zero).

 

Bugger. As you say... too much leting it sit in the garage.

 

stu

oops posted that twice.

 

yeh possibility. Though I'm not sure they would be too happy about looking at the 300 again. I got the impression last time that it was a bit too complicated for them. They did a good job, but they were were concerned that they could easily bugger something up because they didn't have the knowledge about the electronics, etc for the 300s. I'll have to have a chat with them and check they are happy to look at it really or would prefer if I found somewhere else... whereever that would be.. I went to warrior motorsport for something, but by the look of their workshops I wouldn't trust them with my electric scooter never mind the Z.

 

Anyway, its a couple of hours job, so wouldn't want the beast sitting outside for a week. I'll limp it home tonight (leave early to get a quick run home), and sort it out when I get back. Got here ok, so I'm assuming it won't overheat with a quick journey home.

 

stu

 

p.s. went by you coming out of your drive yesterday in my mundaneo*.. 300 was looking shiny.

 

*tried a 'short cut' through bramford onto A14 at claydon to avoid roadworks as they resurface lovetofts drive.

If the thermostat was failed then either the water will take ages to heat up and wont regulate itself properly - or you engine will overheat.

 

The temp sensor for the ECU and the sender for the dash are two seperate items. The one for the dash is the little black one - try giving it a good clean and see how it goes.

When I read the first post I thought it was a dicky gauge sender... but you imply later you can take the rad cap off whilst the temp needle is on warm (ie almost horizontal.) I'd say there's something seriously amiss there - no pressure in the system!