Coolant Pressure Issues

[gL3nJaMiN88]

ok i've looked everywhere on this forum for some how to fix my issues but i cant find anything .

First things first my car runs hot , and i mean hot . I though it was just how hard i drive it but even driving short distance with no boost it gets around 95*c and when i boost it i can sometimes see 110*c.

OK the Waterpump + Thermostat 76*C Opening has been changed and also i put new coolant in with new hoses + Clamps .

Now i never noticed until one day someone pointed out that i have NO PRESSURE what so ever in my radiator hoses . Doesnt matter if its a 20 min drive or a 2 hour drive i have sweet shit all pressure in my hose .

I mean i can take radiator cap off whenever i feel like it with nothing over flowing . THe coolant is right at top of radiator just like it should be + my overflow bottle it full right to max!.

I thought it could be my radiator cap , but its a brand new NISMO item that i purchased like 4 months prior..

i've tried finding a simple post how to bleed system but no one has a post on it ? only site i found was some other stupid sight that said to jack car up and take cap off while the heater is on and it will bleed? but yeh didnt do anything .. Tried that little bolt on manifold but i can take screw out and nothing happens .

Now before you say its the waterpump , it cant be .. when i rev the car you can see the coolant moving around the radiator very fast.

I've rang every radiator place and they said they have no idea what it is? has anyone had a similar issue ?

what could it be ? Im not loosing any coolant either

[simpletool]

Radiator cap or radiator sealing issues (do you have after-market radiator?) Does the cap SEAL against the lip inside the radiator? Check for indent in the inner radiator seal - the inner one that is sprung. (And yes, I read every word of your post).

Related issues - when hot does the overflow bottle fill-up more? If not there must be a large amount of air in your system.

Take off the vertical screw that is between the PCV valve and plenum (it is at a high point). Take off the radiator cap - turn on your engine. Pour water into radiator - etc etc. Rev engine a little with throttle - bubble should come out either radiator or screw (out screw back in a few turns and repeat to get smaller bubbles out).

This process is better if car is SLIGHTLY pointing uphill.

[STATUS]

it can take 15mins to bleed up to the bleeder bolt on some cars, but honestly if you driven it a few times and topped it up it is really the same thing.

Another issue could be the new thermostat, we only use genuine nissan ones as we found about 7 in 10 tridon or similar aftermarket one did not open properly in the rbs' and sr's.

get your rad checked too.

We had a similar issue with a customer who see regular track days he had brand new china brand radiator (2 months old) it kept over heating so i changed everything around it only to find the radiator was useless, put a new one in (ASI) and car was fine

Edited November 24, 2009 by URAS

[payback21]

Thats true, it does take a little bit of a while to bleed from the bleeder on the manifold.

It pays to have the heater on when bleeding it so it can get the air out of the heater system if there is any. Water should trickle out of the bleeder when its got the air out.

It does sound like a air lock. You do want to watch that you dont over heat it and warp the head. Thats the least thing you want to happen.

[Moodles2]

Not a fan of Nismo or aftermarket rad caps that bring the pressure up to 1.3kg/cm2, just puts more strain on the hoses, increasing risk of them popping them off for afew extra degrees before the coolant boils.

[shyr33]

Hey mate so did you change to a new waterpump? What brand was it? Now I am no expert but isnt it the water pump which will create the pressure in the system? And if you have a properly sealed system then there should pressure.

So either the pump is not creating enough pressure or the pressure is leaking outwards somewhere and as mentioned one of the main reasons for a car running hot is air in the system or you have a very fouled radiator. That happened to a friend of mine. Car was overheating, took of the radiator and gave it to a radiator shop and got it cleaned. They said it had alot of shit in it, put it back on the car and ran ok.

[funki_munki]

i recently bought a new radiator for my 32 got a koyo rad direct replacement for 270 cost price from my mums work, the guy also cleaned and straightened out my old one and it was 70% blocked. as moodles2 said a .9bar rad cap will suffice,i got a cpc one and the difference between the old and new was heaps the spring on the old was soft the new one is firm.

as for bleeding the system,i used a coke bottle that was chopped and held that in the radiator and filled that up and waited for the bubbles to pop up,after that i just filled the resevoir up and i keep a eye on it for the first couple of days just to make sure.

[Beer Baron]

Hey mate so did you change to a new waterpump? What brand was it? Now I am no expert but isnt it the water pump which will create the pressure in the system? And if you have a properly sealed system then there should pressure.

So either the pump is not creating enough pressure or the pressure is leaking outwards somewhere and as mentioned one of the main reasons for a car running hot is air in the system or you have a very fouled radiator. That happened to a friend of mine. Car was overheating, took of the radiator and gave it to a radiator shop and got it cleaned. They said it had alot of shit in it, put it back on the car and ran ok.

no it's heat which creates pressure in the system. the hotter the coolant/water gets the more it expands. water kept under pressure raises it's boiling point. once the heat gets so much that the pressure exceeds the spring pressure of the cap then the cap releases pressure (water) which then boils in the overflow tank immediately as it's already over 100C and no longer under pressure any more. all the pump does is push water around, it's the heat that creates the pressure and it's for that reason (to enable the coolant to reach higher temps before boiling).

[shyr33]

Ye that makes sense (I have been working to much with large water pumps in the water industry) thanks Beer Baron. What pressures do the cooling system operate at (is that 0.9bar on my standard cap?)

[Duncan]

yep that's right, and the pressure of the cap dictates the maximum temp the system will get to. Once it reaches the cap's pressure it will let water out and the coolant won't get any warmer. 1.2 bar is about 120o and 1.3 bar about 132o. Assuming something else like a heater hose doesn't crack under that pressure first of course.

[blind_elk]

Pumps create pressure. Pressure (differences in pressure) causes fluids to move.

The expansion of water when heated, even in an enclosed space, is insufficient to create the kinds of pressure you see inside a cooling system. And there will always be some air inside the cooling system, which will absorb the pressure increases far more readily than water will.

Back to the OP - I think you will find that the water pump impellers are cactus, and the water is not circulating properly.

[gL3nJaMiN88]

hey guys i have fixed my problem all together .. I purchased a 45mm aluminium radiator from autobarn . The brand is autotecnica and it is very well made .. And the price was pretty good aswell only 200 for me as i work there .. I flushed the system until the water that came out was as clean as it went in .. I only used demineralised water aswell .. Then i put new radiator in keeping original shroud , and it only took like 10 mins .. Put new nulon RED coolant in with water .. Checked my coolants Mv to make sure i had no electrolises .. Which i didn't and car runs amazing now .. Builds up pressure nice and i don't see a temperature over 85*c on hot day giving it some and on cool nights just cruising around i see around 78-80* at most ..