Heating issue 4.8

[Peter Connan]

Just a question: was there any noticeable difference in performance on the days the car got hot?

I am thinking it may be an ECU issue, that either timing or fueling is being changed. Running lean and incorrect ignition timing are both issues that can causd a petrol engine to get hot.

If the cause was a head gasket or a crack, the symptom would be "boiling" and a loss of water rather than an increase in temperature.

Alternatives could be a thermostat that is not opening, or an air-lock in the cooling system.

[Craig Lord]

Just a question: was there any noticeable difference in performance on the days the car got hot?

I am thinking it may be an ECU issue, that either timing or fueling is being changed. Running lean and incorrect ignition timing are both issues that can causd a petrol engine to get hot.

If the cause was a head gasket or a crack, the symptom would be "boiling" and a loss of water rather than an increase in temperature.

Alternatives could be a thermostat that is not opening, or an air-lock in the cooling system.

Hi Peter
I didnt really notice any drop in performance but I suppose it's possible.

I saw a post on the patrol Facebook page where someone suggested that a failing fuel pump could also be the cause of increased engine temperatures so that will be on the list if everything else checks out. Nissan also changed my main engine wiring harness 3 weeks back because they said it was brittle and causing alot of faults. Apparently that solved the faults issue so I hope the ecu is ok... the thermostat was changed 4 days ago but didnt solve the issue as well as the viscous fan hub and the radiator cap.

The only things left to be checked on the actual cooling system is the hoses for blockages, the radiator is new but is it correct? and lastly the water pump but the car has been bled twice by nissan in the last 3 weeks so I assume they would have noticed if the waterpump was not performing well?

If it was boiling would it boil out into the radiator reservoir bottle? If so mine doesnt do that.

[NoPressure]

Just a question: was there any noticeable difference in performance on the days the car got hot?

I am thinking it may be an ECU issue, that either timing or fueling is being changed. Running lean and incorrect ignition timing are both issues that can causd a petrol engine to get hot.

If the cause was a head gasket or a crack, the symptom would be "boiling" and a loss of water rather than an increase in temperature.

Alternatives could be a thermostat that is not opening, or an air-lock in the cooling system.

Hi Peter
I didnt really notice any drop in performance but I suppose it's possible.

I saw a post on the patrol Facebook page where someone suggested that a failing fuel pump could also be the cause of increased engine temperatures so that will be on the list if everything else checks out. Nissan also changed my main engine wiring harness 3 weeks back because they said it was brittle and causing alot of faults. Apparently that solved the faults issue so I hope the ecu is ok... the thermostat was changed 4 days ago but didnt solve the issue as well as the viscous fan hub and the radiator cap.

The only things left to be checked on the actual cooling system is the hoses for blockages, the radiator is new but is it correct? and lastly the water pump but the car has been bled twice by nissan in the last 3 weeks so I assume they would have noticed if the waterpump was not performing well?

If it was boiling would it boil out into the radiator reservoir bottle? If so mine doesnt do that.

I have NO expertise in this, but it doesn't make sense that when it works harder its cooler if there was an issue with the head.

Towing heavy, means a sagged rear suspension, causing front nose lift. Air moves up - thus it sounds to me like air entrapment.

[Peter Connan]

The only things left to be checked on the actual cooling system is the hoses for blockages, the radiator is new but is it correct? and lastly the water pump but the car has been bled twice by nissan in the last 3 weeks so I assume they would have noticed if the waterpump was not performing well?

If it was boiling would it boil out into the radiator reservoir bottle? If so mine doesnt do that.

Lets try and explain it this way: a head gasket leak or crack in head or block means something is going where it shouldn't.

Water can get into the oil or oil into the water. Either is visible by inspecting radiator or dipstick.
Combustion gasses can get into the water or the oil. Because combustion pressure is orders of magnitude higher than either water or oil temps, this should lead to visible issues. If it's getting into the sump, you will have lots of blow-by, and things like the dipstick blowing out. If it's into the water, you will have bubbles in the water if you take the radiator cap off with the engine running. With the cap on, the pressure will rise higher than the cap's max, causing pressure to go into the expansion bottle and from there "boiling" out. This WILL lead to water level going down. Also, it is not actually boiling(ie temperature need not be high).
It is also possible for water to get into the exhaust or inlet (low-pressure zones). This causes puffs of white smoke when changing gear and also water loss.

Keep in mind that these symptoms can change as the damage propagates, but it never gets any better. Thus it can't have issues one day and be fine the next.

The same is true for the water pump. It is either good or it isn't.

Things like a fuel pump on the way out, a ECU or wiring acting up, a sticky thermostat or air entrapped in the cooling system can all come and go. Thus one of these is your problem.

Take note that there have been cases of brand-new thermostats acting up recently, so just having replaced it is no real guarantee that you have definitely eliminated that from the search.

[Craig Lord]

Ok gentlemen I went out and got myself a compression tester and today I ran the tests. (Engine was cold)

The results are as follows: (in PSI)

Cylinder 1: 165
Cylinder 2: 165
Cylinder 3: 165
Cylinder 4: 165
Cylinder 5: 165
Cylinder 6: 161 (just slightly over the 160 mark on the guage)

I am battling to find the compression specs for the 4.8 but hopefully one of you will be able to tell me. The fact that they are all similar gives me hope. I'm concerned about No. 6 but I'm hoping it's still within limits.

I also found leaking pipe underneath the throttle body that I couldn't see before without taking it off.

2 days ago I also took the cap off the radiator and started the car up from cold to watch for bubbles. At first there was one or 2 Bigish ones but soon it became 2 or 3 very small bubbles every 2 minutes or so. I ran it with the cap off for a further 20 minutes but still the bubbles came sometimes none for 5 minutes or so then a couple of small ones and then nothing again. I took a video which I can post to the Facebook page. I wander if the system is sucking in air from somewhere else maybe that leaking pipe under the throttle body.

My father is bringing another chemical tester over Christmas so we can test the radiator for carbon dioxide/monoxide again to make sure there are no gasses getting into the coolant.

Either way I'm quietly confident about the compression test results until I can find the specs to confirm. If the results are within spec then it contradicts what silverton said but like I said earlier I am a bit skeptical about the way that test was done.

I forgot to mention in previous posts about the symptoms that it only acts up after driving for quite a while like after 100km or more so if it is air in the system it's taking a while for it to build up enough steam to cause the issue.

[Peter Connan]

That is AMAZINGLY close and certainly within the specs for cylinder variance. No idea what the compression should be, but that sounds very healthy to me.

Also, I will say this again: any crack in the metal or a head gasket issue CANNOT "get better" from one day to the next. The symptoms will either stay roughly the same, or get worse.

I am convinced that your basic engine is healthy, and your problem lies somewhere else.

[Tinus lotz]

Dude pick up the radiator and check again really sure thats your problem

[AndrewA]

This may help, taken from the manual for the Y61 series

[AndrewA]

Sorry the wrong scan :)

[AndrewA]

I always get confused if its for the Diesel or Petrol the manual doesn't state that