Coolant - Engine wont warm up - stays cold

[maxhag]

I had it all functioning as it should this afternoon, after the bleed. Engine would hold 88-90deg at idle, with the fan set. This was after the bleed and another10-15 mins of idle.

When I went out for a drive before, about 6 pm. It would have been 0-2deg outside. After 30 mins normal driving, my water temp at thermostat got to 70deg. Oil temp was around 55-60deg.

So this tells the answer I guess. As Rhys and others said, the radiator and new/better oil cooler must be acting as a very efficient heat sink, and combined with Canberra weather.
I tried 2 radiators from the pile, and they both had corroded badly. So I havent tried another radiator yet.

I totally understand the principles of this, but I just couldn't believe that the generic ebay AE86 radiators could be so differant to one another. As I've said, This engine, and others I've built, have had these radiators, along with many people I know, and never had this occur.....

Well, I still need to try another radiator to confirm this, but I really cant think of anything else.....

[sundee]

Sam - sr20
Jojo - 4ag

Both same issues.

4a doesn't have a bleed point
Sr does.. Assume you used this Sam ?

After bleed - jojo's heater worked but same opp temps as before?
Sam, did u see any change?

[sundee]

Seems like your set Jojo?

[sam92]

I don't use my bleeder point because my radiator sits higher and yes I saw improvement but ill know if it really has done the trick in the morning when I take it for a drive in the cold and see if it warms up. Fingers crossed but I think the bleeding has done the trick

[maxhag]

Yeah Joel, only improvement is that I have heater now....


First, I am also going to bypass the oil cooler, and re-test.
If not "improved", I will pull a radiator out of another car in the yard to try

[LittleRedSpirit]

You may still find the bleed point will allow air out, it can become trapped. Id tend to assume Nissan put it there for a reason, rather than just waste the effort.

And another thing, imagine how cold the water in the radiator really is when it comes in on the first thermo cycle, its got to be cold if it spends 5-10 minutes inside a massive aluminium heat sync that is travelling at possibly 100klm/hr in a -4 degree air stream, you really do need the thermostat to open slowly.

[nelpd96|]

JoJo, for what it is worth go back to first principles. Forget what the temp sensor/guages are telling you for the moment.

The water gets hot by transferring heat from the block, it is then passed through to the radiator to cool it before going back to the engine.

The flow between the two is controled by the thermostat.

The fan is auxilary cooling to assist in airflow over the radiator and facilitate heat transfer.

So step 1.

What is the block temperature when running? I have an IR temp gun if you need to borrow it. Compare this to one to runs normally like mine.

Step 2.

Once you know roughly what sort of block temp you should have I would run the engine up with the water pump belt off to get the block temp up to where you should expect it to be. Once you are happy with that then hook the belt back on and quickly run it up.

Two things should happen, the thermostat should open and the water temp should be up around the 85-90 mark.

If that checks out you know that you temp measurements are ok and that the block is transferring heat. Go to step 3, if the temp is not what you would expect then calibrate the sensor again in some boiling water, they work through resistance so it is possible that there has been a change in the wiring resistance either though difference earthing for this engine or if something was crushed in the previous accident.

Step 3.

The question then becomes why is the temp dropping back down, this is fundamentally due to the rate of heat transfer between the engine and water is less than that between the water and the radiator.

This situation is brought about because the flow of water is too high, either because the water pump is moving the water too quickly or the thermostat is not regulating the flow of water properly.

Step 4.

Easy way to check is to grab a set of vice grip or a clamp of some description and clamp off the hose that is coming out of the thermostat so induce an artificial restriction. If that works then you know that you thermostat is not slowing the flow of water enough.

I have tomorrow off so if you want me to pop around and have a look let me know.

Cheers
Paul

[maxhag]

AND THE WINNER IS:

ALEX!!!!!!!!!!! (Blinded)

The oil cooler......



Which really makes more sense, as the oil cooler was very differant to the old one, yet the radiators are virtually the same........

It was also the biggest and best quality oil cooler I have even fitted to any car. I simply did not realise how good the unit could perform just acting as a heat sink without flow.....

[maxhag]

After driving around for a while, both normal and the odd giving it a bit, It all seems alright.

*Constant 80-84deg at thermostat with fan set to come on at 90deg
*Temp at top hose is about 10deg cooler than at thermostat across the range.
*Oil is holding a constant 85-90deg.....

[LittleRedSpirit]

Well done. Did you remove it altogether or just thermostatically control it?