Water temp needle goes up only after 100km/h

[P4trol]

A bit of a long read.

The vehicle: 99 GU series 1, RD2.8t, white.

Problem: The water guage starts creeping up at about 105km/h. It is worse in 4th.

Recently I have replaced the MAF sensor, and it fixes the sluggish problem I had. The oil leak (unrelated, from the front of the sump, where 2 or 3 sump bolts are stripped) does not occur after the MAF change and also the intercooler has the oil cleaned out (and importantly the charge air temp sensor). Belts have been changed, new radiator hoses, water pump, and fluid. Fixed the problem with coolant not being sucked back from the overflow tank. New coolant.

The acceleration is welcome since the change. I can't get the water temperature to move until it hits 105/110km/h on the flat. Ambient temperatures 36-38 degrees. Ordinarily the temperature needle doesn't move from the 11 o'clock position, just to the left of the symbol on the water temp guage. It doesn't come down that quickly when you take your foot off. I realise that it is operating in adverse temperatures, but I believe the cooling should be able to keep up. When it is doing these speeds/temps, you can push your foot further, and it actually accelerates.

It hasn't done this before. I have my own theories, and am still ironing out things from the previous owner.

I believe it has been bled properly.

The injector pump - it is mechanical? Would it be likely to inject too much fuel at high rpm? (and how much would a brand new - off the shelf - one need tuning before placing in the engine?

Coolant concentration: I bought two bottles because I emptied all the coolant. The concentration would be up around 70-80%. Would the greater than recommended concentration have an adverse effect?

Apart from the normal fluids change and IP calibration, what further can be done (without a chip) to 'tune up' the engine?

Thoughts? Opinions?

[Dales300exc]

Water is the best at cooling. After about 50% mix you start losing cooling efficency. In hot conditions id drop back to 33%.

[Mud Gecko]

Are you reading off the factory temp gauge? I find the water temp gauge not very accurate, also it's hard to know if over-fueling if you don't have an EGT gauge. I found my BIL's GQ2.8 runs higher EGTs than I do (zd30).

Did you replace the fan clutch?

[04OFF]

Someone has not removed the thermostat have they ?

[P4trol]

That was the other thing I replaced, genuine thermostat.

But not the fan clutch. I was a little confused as to what the fan clutch should do when the engine was off: mine doesn't spin very much when you give it a spin. Did buy a bottle of silicone oil to try and rejuvenate it though.

Might have to put an egt gauge on.

[my third 256]

doesnt concentrate bottle say to mix at 30%

[menace 2]

I use Nulon and it says...standard 33%...boiling point 127 degrees C to minus 18 degress C.......extreme 50%....boiling point 132 degrees C to minus 37 degrees C

[P4trol]

It does say 30 - 50%, (and as said a higher concentration increases the boiling point.

But the temp gauge isn't measuring boiling point.

Is the coolant less efficient at higher temperatures?

[threedogs]

you could buy a Thermo gun ,aim it at the top of your radiator,
might need to fit a heap of gauges to monitor your motor. I
wouldn't be relying on OE gauges, or red lights.
Full set oil press ,water temp, boost and EGT would be my starting point.
You may find driving by your gauges advantageous, in the long run

[the evil twin]

I' ve not had the pleasure of owning a 2.8... had one or more of just about everything else tho.

Soooo... speaking generically I would suggest that you may need to get the radiator rodded.

If the fan doesn't spin much on shutdown then the clutch sounds as tho it may be OK. It def shouldn't freewheel longer than maybe 2 seconds
If you had issues with the coolant plumbing, hoses etc then you can bet the rad was worse still
If the vehicle was sluggish and a MAF service fixed it I reckon you are now seeing more fuel
More fuel means more heat and more speed means more load means even more heat

I would also check for head issues. High speed overheating can be indicative of a head starting to go

I would definitely dilute your mix down some more (as prev mentioned). Whilst the coolant boiling temp is raised I am led to believe the heat transfer efficiency is adversely affected. Could be wrong about that tho

[threedogs]

hope you haven't used two different coolants cause
if that's the case it will turn to Gel very fast

[P4trol]

Same coolant used. I will try diluting it and check the difference.

The best way to test the head is...? Compression test?

And is it best to test the fan clutch when the vehicle is stopped (and spin by hand), or as above, measuring the time before it stops spinning?

[NP99]

While straight water is no good for an engine, I'd drain the coolant, fill with water and take it for a run and see if the problem is still there. When it cools replace with correct % of coolant.

[P4trol]

Bit of an update:

The symptoms became more apparent after fitting some chunky mud tyres. I replaced the radiator with a 3 core aluminium job from evilbay. I had pondered about the viscous fan before enough to buy some Silicone oil to fill it up. It was fairly easy in mine. Suspect someone has done it before.

So now the symptoms have backed off to appearing after $1.20 to $1.30

Fairly pleased with that, because it's a small engine after all.

Speed kills:

Drive a 2.8 and live longer!