Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: Entwood on 31 July 2010, 16:09:47
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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
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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 :-/
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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.
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drive faster on motorway and see if it helps when going to slow speed stuff? :D :)
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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. :-/
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I had a Veccy do that a few years ago, but, that was purely due to a lack of coolant (hose split)...
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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?
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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.
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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.
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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.
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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
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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 100oC ... no high temp warning light.
I can't offer an explanation for Nige's problem though, but can't see it being the grille.
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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 100oC ... 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 :-/
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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
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....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.
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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 :y
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....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.
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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 :y
Taken as you intended the question... Why would it work? No worries Andy :y :y
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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.
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Wonder if this actually happened when stationary at the roundabout. The temp gauge on Omegas is delayed (and damped) by approx 12-18s...
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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
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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..
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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.
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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
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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.
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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.
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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 ??
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No one any thoughts on the waterpump idea ??? :(
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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 ;)
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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
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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.
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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... :-/ :-/
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Does it do it on petrol and LPG?
Just wondering if the LPG fuelling is a little lean.
Kevin
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Does it do it on petrol and LPG?
Just wondering if the LPG fuelling is a little lean.
Kevin
No idea ... :( Never thought to switch over to petrol....
might have to try next weekend .. if I can find a hill big enough between here and Somerset ... :)
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Could it just be a case of an air lock with low coolant, fine with low revs / small throttle openings, but give it some stick and rev it a lot more, the sudden rush of coolant in the block going to the back of the motor could give the sensors a false reading? maybe?, I had a very similar problem 3 years ago and that's all it was.
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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... :-/ :-/
I'm not towing, bet it happened to me after climbing a mountain hill and stopping.
The rad was quit dirty and the only thing help is to dismantle and clean.