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[Entwood]

Motoring down in France over the past few days had 2 small "hiccups" ... wonder if anyone has any ideas...  not that I'm in any position to do much ...

Scenario was virtualy the same both times...  After over 100 miles of motorway cruising at 90kph (56mph) with the 'van on the back, during which the water temp was a constant 92 - where it usually sits when towing - came off the motorway and had a fairly steep rise off a roundabout exit that made her drop into 2nd to pull up the hill. Within seconds the temp just went right up to hard against the top stop, moving from 92 to max in about 2 seconds red light on as the needle passed 100 on its way to silly numbers. Unsafe to pull over, so instantly off the power, heater to full hot and heater fan to max, continue up the hill at about 10mph, very light throttle. Within 15 seconds the temp started to drop at about 1/2 the rate it went up... back below 100 (light out) after about 20 seconds, back to the "normal" of 92 after about 30 seconds. From then on beheved impeccably. Water level and oil level (engine) checked and all spot on.

Have done over about 600 miles towing and this happened just the twice. Done about 80 miles solo and the temp hasn't moved from 87.

I'm wondering if the autobox level might be a tad low, so its running warm, and dropping into 2nd "dumps" a load of hot oil into the coolant system and the fans are "late" to respond as they are getting their temp info from a different place ??

Probably talking rubbish .. but anyone any other ideas ??

It's an excuse to come to the bar for a beer to read your responses anyway

Nige

[tunnie]

for it to rise as fast as your saying, sounds like its maybe dodgey temp sensor? Or way its reading it? Can't see it getting that hot in 2 seconds  :-/

[Andy H]

I can see how hot auto oil might quickly raise the temperature of the water returning from the radiator to the back of the block (where the coolant sensor is) before the engine thermostat (at the front of the block) knows anything about it but surely you would have noticed the effect on previous towing trips :-/

I wonder if your radiator is less effective than it used to be and can just cope with steady towing at 56mph (when the airflow is minimal) but needs extra assistance when everything is hot and you need to dump more heat climbing a slip road with no forward movement to shift air through the rad.

Driving solo you will be travelling faster at smaller throttle openings so the rad finds it easier to dump the heat.

[tunnie]

drive faster on motorway and see if it helps when going to slow speed stuff?  

[feeutfo]

Sounds electrical to me, can't see temp rising and falling that quick. But then I have no experience with the cooling system other than the usual leaks.  :-/

[Psychoca]

I had a Veccy do that a few years ago, but, that was purely due to a lack of coolant (hose split)...

[vbelen4]

I agree that only reason for rising and falling the temp so quickly is a momentary lack of coolant on the sensor. Maybe the circuit is not correctly pressurized and coolant is boling?

[omegadan67]

i had a similar "problem" a few years ago with my 2.5 auto estate while cruising at a constant speed temp sat at 90 when slowed down or waiting to exit a junction temp wwent right up to 100+ but as soon as speed got over 30 mph dropped quicker than a lead ballon back to 90. never did find the reason why and never had it happen on any other omega either. still have the car in the family and they tow regular with her they have the same experiance going up telegraph hill at the bottom of the m5 no route to cornwall.

spent loads of money trying to find out the cause at the dealers didnt get any answers just bills.

[Evo]

My 2.5TD had large temperature swings when using the power up hills (I live in the Chilterns) ... eliminated with a new rad. Ties in with Andy H's diagnosis of a marginal radiator.

[Mr Skrunts]

Normal driving, normal temp.

Steeper exit road, with van, slower speed, less wind flow to cool rads.

Seems the car is working fine and doing the job inteneded.

If not sure when you get home, check/change gearbox fluid (maybe old fluid is not as efficient) do a couple of flushes on the rad and rest of system, maybe even change the sender unit. 

But also consider fitting a fan override switch if it is possiblem then if you are passing over hills/mountians you can swith the fan(S) on manually as and when required.

[Lazydocker]

I have exactly the same happen to mine Nige... Still not gotten to the bottom of it although I was thinking about changing the Grill from the Elite one to something bigger after a suggestion from TB

[Andy B]

I have exactly the same happen to mine Nige... Still not gotten to the bottom of it although I was thinking about changing the Grill from the Elite one to something bigger after a suggestion from TB

I can't see the grille having anything to do with it. After our first trip out with the caravan on tow I noticed that on one particular looooong slow hill that the temp was heading skywards. Rad was flushed though with limited success  but was eventually replace due to a leak. Since then though I've towed both here & France (in high 20'/low30's) and the most that's happened is that the temp gauge has gone up to around 100^oC ... no high temp warning light.
I can't offer an explanation for Nige's problem though, but can't see it being the grille.

[Lazydocker]

I have exactly the same happen to mine Nige... Still not gotten to the bottom of it although I was thinking about changing the Grill from the Elite one to something bigger after a suggestion from TB

I can't see the grille having anything to do with it. After our first trip out with the caravan on tow I noticed that on one particular looooong slow hill that the temp was heading skywards. Rad was flushed though with limited success  but was eventually replace due to a leak. Since then though I've towed both here & France (in high 20'/low30's) and the most that's happened is that the temp gauge has gone up to around 100^oC ... no high temp warning light.
I can't offer an explanation for Nige's problem though, but can't see it being the grille.

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.

Looks like I may have to think about a new rad then as I've flushed mine twice. Mind you, it doesn't seem to have any cool spots  :-/

[Kevin Wood]

Gearbox cooler is a separate radiator on the 3.2 Auto so we can probably discount any involvement of the gearbox.

It's not physically possible for the engine to heat 10 litres of coolant as fast as described, IMHO.  I wonder if it was some sort of airlock?

ISTR you have a long run of hose down to your vapouriser. I wonder if that airlocked somehow, preventing coolant flow over the sensor. Would still mean that the coolant was at that elevated temperature, though, which would point more to an airlock in the rad. circuit.

Failing that, the coolant temperature sensor wire is shorting to ground. (probably the likeliest scenario in the event of no other overheating symptoms IMHO).

Kevin

[Andy B]

....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