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[Lazydocker]

....The suggestion was because there was a recall on tractor elites for the same problem and replacing the elite grill for the larger surface area of the standard one was the fix.
 ......

I didn't mean to poo poo your suggestion  Earlier Senators had part of the chipper grille blanked s you couldn't see through it, this could result in higher engine temps too. They all then got a 'full flow' grille 

Taken as you intended the question... Why would it work? No worries Andy

[Evo]

Kevin Wood says 'It's not physically possible for the engine to heat 10 litres of coolant as fast as described, IMHO'.

It's interesting if you do the maths. A 3KW kettle heats one liter to boiling in 2 minutes. A 3.2l Omega engine has a max power output of 160KW. So the engine could raise 10 liters of coolant from 90 to 100 centigrade in 2.25 seconds at peak output if the radiator was totally non functional.

So I guess it makes you aware of the need of a good functional radiator & fan when pulling a van in a hot climate.

On reflection this could suggest that the problem here is that the fan is not fully functional or the airflow is not clear thru the rad as the problem occurs at slow speed.

[TheBoy]

Wonder if this actually happened when stationary at the roundabout.  The temp gauge on Omegas is delayed (and damped) by approx 12-18s...

[Kevin Wood]

Kevin Wood says 'It's not physically possible for the engine to heat 10 litres of coolant as fast as described, IMHO'.

It's interesting if you do the maths. A 3KW kettle heats one liter to boiling in 2 minutes. A 3.2l Omega engine has a max power output of 160KW. So the engine could raise 10 liters of coolant from 90 to 100 centigrade in 2.25 seconds at peak output if the radiator was totally non functional.

Don't forget it's got to heat 150kg+ of metal as well, and while the heat output is probably not far off the power output, the engine won't have been delivering anything like full output (as an average) slowing for a roundabout and then accelerating through the gears.

I think it's more likely that either the gauge sender was dry (due to an airlock or low coolant level) and then got doused in very hot water from an overheating engine or that it was an electrical issue and the temperature never deviated from normal.

That aside, thinking about what might have happened, the engine will have come from a gentle cruise to probably a few seconds of coasting off the main road when the heat output is more or less zero. Radiator will have been cooling quite efficiently during the cruise and it won't immediately soak up heat. I wouldn't mind betting the thermostat probably closed when he came off the power. Then a load of power on at a relatively low speed would have required the 'stat to open quickly as we have high heat output and the radiator not cooling efficiently. Possible the thermostat stuck closed at this point, I suppose? :-/ You would certainly get rapid cooling when it opened. I'm just not convinced that it would heat up that spectacularly.

I am assuming the coolant level was, and remained, correct, of course.

Kevin

[cem_devecioglu]

if all fans working ok, imo faulty thermostat..

some years ago I also had heating problems when climbing the mountains.. although the mechanics didnt agree I changed the thermostat , it solved the problem..

also the drop in  temperature after opening the heater prooves there is a problem in coolant flow  .. the heater matrix size compared to radiator is very small..

[aymen]

two weeks ago I had been suffering from sudden rise in my 2.2 omega temp. it got up to red light, but I discoved the problem was termostate. when I removed it and checked in boiling water it prooved not to open for water to pass.

[Kevin Wood]

if all fans working ok, imo faulty thermostat..

some years ago I also had heating problems when climbing the mountains.. although the mechanics didnt agree I changed the thermostat , it solved the problem..

also the drop in  temperature after opening the heater prooves there is a problem in coolant flow  .. the heater matrix size compared to radiator is very small..

Yes, that made me wonder too. Coolant flow past the gauge sensor requires coolant flow through the bridge and into the heater matrix or bypass circuit. If this circuit were airlocked or blocked in some way (and it has a long run of pipe to the evaporator on this car) you could get a hot spot at the back of the cylinder heads that has poor coolant flow, and localised heating near the sensor. Once it clears, coolant at the temperature of the rest of the system would begin to flow and indicated temperature would be rapidly restored to normal.

HBV could well be worth a look, then, because this might not be fully opening the bypass circuit when deactivated.

Kevin

[Entwood]

Thanks for all the thoughts ... more work to be done on return to UK methinks.

Just to throw things into the pot ..

Thermostat was replaced by Daz & Pete just about a year ago if memory serves.., HBV was replaced 3 months ago.

The Rad cooling fans certainly kicked in on MAX .. but after the temp had passed 100. Today I left the motor running in a temp of 38 and full sun, aircon off ... fans seemed to go to high speed at 97.

Sort of goes along with the idea that the indicator sensor is doing "different" to the fan sensor.

Tow back next week has some pretty large inclines, be interesting to see what occurs, certainly solo and "pressing on" [kick down to 3rd and hold it to naughty speeds] up a long incline today the temp didn't move above 90.

[fogrider]

Just towed my caravan for the first time on a hottish day. Reading all the previous posts has given me an idea: since my aircon does'nt work ( I don't need it ) why can't I remove the air con rad which will allow far more air to hit the main cooling rad ? it was running into a head wind showing just under 95 degrees at times. Would also let the fans do more good. Any comments guys ?
2.5td estate. Manual.

[Entwood]

We is home now, and a bit more info ...

Towing home, heavy , with some very long climbs over the last 2 days, the following was noted.

If the revs were kept below 3000rpm, even on long climbs, by light use of the right foot, and allowing the speed to drop, the temp never rose above 91°C. If the revs were allowed to rise to 3500 rpm the temp then started to rise, reduce revs and the temp dropped back.

On one occasion I deliberately "kicked down " to over 4000 rpm .. the temp started to rise very rapidly, quickly reaching 100°C - it dropped back rapidly on "easing off" to below 3000 rpm.

As the two occasions when it overheated, details in the first post in the thread, were on "booting it" off a roundabout, I'm thinking the "heater cooling" aspect is misleading/coincidental as the heater was put to "HOT" at the same time the power was reduced.

Now what might cause this ??

The cambelt was changed when I bought the car at 80,000, but I have no idea if the water pump was changed at the same time. As the car has now done 100,000, probably on the original water pump, could it be that the water pump is getting "tired" and inefficient at high RPM

My thoughts are that the pump is not moving coolant fast enough at high rpm, but seems to be fine at low RPM as the temp drops rapidly once RPM is reduced

Any one any thoughts/ideas on my musings And, how to check more accurately if this is the problem ??

[Entwood]

No one any thoughts on the waterpump idea

[Lazydocker]

No one any thoughts on the waterpump idea

Unlikely IMO... Generally they work or don't. Possible only a couple of fins have broken up on the impeller I suppose :-/ :-/

But seems unlikely as mine does the same thing and my W/P was under 2 years and 35k old when it started

[zvi]

No one any thoughts on the waterpump idea

when I had this, I checked the thermostat, waterpump, replaced the heat sensor, flashed the system.
noting helped, only dismantle the rad open it and did thorough cleaning of all the tunnel inside.
did in a garage quite cheep

[Andy H]

IIRC the waterpump has a stainless steel impeller that is extremely unlikely to degrade or throw blades. Occasionally pumps fail because the impeller becomes loose on the shaft (which can be difficult to diagnose) but I don't think the Omega is prone to this :-/

My money is on the radiator. In addition to possible poor heat transfer on the water side (due to silt or radweld) the air side can deteriorate badly due to corrosion attacking the fins and bugs and debris blocking the airways.

[Entwood]

Okies .. not the waterpump then

But why does it only run hot when towing and booted to over 3500 rpm ?? and cool very rapidly when the rpm drops ??

If it was a blocked radiator, either internally or externally, giving poor heat transfer, then it would take a while to cool I'd have thought ??

The car towed to The South of France 2 years back with much heavier work, and to The Lakes this year without any hiccups. I don't see it silting up that fast ??

It had a coolant flush/change in May 09 just after the thermostat change. (15000 miles) so it might be worth doing another and seeing what comes out I suppose...

Puzzled of Wiltshire...   :-/ :-/