Vectra C 1.8 16v petrol - thermostat and oil

[mointainwalker]

I was back _in the UK a few weeks ago and had the full cambelt/auxiliary belt plus w/pump/tensioners replaced @100 000 - this at a "known" garage.

On the return journey - immediately on fast dual-carriageways/motorways - I noticed fairly quickly that the temp gauge wasn't moving off its stop, and only did so when I slowed down and was driving through Dover town 70 miles further on*. This seems like a hell of a coincidence, but can anyone think of any reason why a change of coolant should induce a thermostat failure ?

Now, a few weeks later, with 15 C weather the other day in the valley, the needle rose up to about 70 C on the flat , but then hit the usual 90 C when I climbed the mountain to return home. I do very few short trips, mainly longer ones at 25 miles , so would this be a problem if I left it for a few months ? I ask this in the light of a thread I recently read about oil in a Micra where the talk veered onto sludge production at lower temps. I'm looking to keep the car as long as possible, so my question is in the light of "long-term reliability "

Whilst talking about oil, I wasn't able to get the recommended GM Dexos2 5-30 ( which is ACEA C3 ) but bought a store-branded ( like Halfords) 5-30 which is ACEA A5/B5, in preparation for my next change. On returning home i checked this and the store web-site ** says "not recommended" for my car.

I haven't had anything to do with ACEA before , so I looked up the various notations and find that A5 is:

"ACEA A5/B5 oils are Upper Mainline lubricants. They are designed for use in high performance gasoline and light duty diesel engines that are specifically designed to use a low viscosity oil. These oils may be unsuitable for use in some engines.  "

Not included in this, is that these are also regarded as "Longlife" oils for extended periods before change. This oil seems to be the top spec, whereas the C3 Dexos is mid-range. The Longlife aspect doesn't affect me as I'm only doing about 7 000 miles/yr and changing oil yearly.

Anybody have any insight into why this would be "not recommended "*, what might make it "unsuitable for some engines " and what are their feelings about my using it.

* I did stop early on and check coolant in tank.

** I maybe shouldn't pay too much attention to this site, because it also listed the wrong oil-filter for my engine on a previous occasion.

Looking forward to your informed responses

 

[Burnerman]

If your coolant isn't reaching the required temperature, the thermostat is not working (stuck open maybe) or the coolant temperature sensor isn't fully immersed in the coolant - perhaps due to an air lock / bubble. Could the thermostat have been removed? Could it be held open by some debris? Both are unknown factors just now.
One good indicator is how efficient the heater is - this is the first thing to fail due to low coolant. I don't know how easy (or necessary) it is to bleed the cooling system on this engine, but all heater pipes must be almost too hot to grab comfortably - as indeed are the main radiator hoses.
Please keep an eye on the coolant expansion bottle - and check the main radiator level at the cap, which should be brim full.
One test for a thermostat is to run the engine on a fast tickover, feeling the radiator core. When the 'stat opens there will be a full surge of hot water filling the entire radiator. Again, on this engine I don't know if the 'stat is at the top of the engine or even in the bottom hose - positions vary.
Ideally you need to run your engine at between 90 and 95 deg C for condensates to be boiled out of the oil.

Regarding the oil, don't believe all you read - maybe this oil just hasn't been tested on this engine, therefore 'not recommended' is recorded. Personally I'd go for a 5/30 C3 lube and all will be well. Some oils are blended to produce low ash (for DPF's) and also to deal with sump dilution due to excess diesel being injected to burn off pollutants in the DPF. Some are blended to deal with scorching hot temperatures encountered by variable vane turbochargers....the list goes on, and that doesn't include GDi engines which are a law unto themselves.
The A5/B5 lubes are very thin and recommended for some Honda, BMW, some Ford and Volvo engines, and I'd avoid them...using the incorrect oil on these engines causes valve failure
Sorry for the late reply!
Regards
John

 

[mointainwalker]

If your coolant isn't reaching the required temperature, the thermostat is not working (stuck open maybe) or the coolant temperature sensor isn't fully immersed in the coolant - perhaps due to an air lock / bubble. Could the thermostat have been removed? Could it be held open by some debris?

The A5/B5 lubes are very thin.........

I don't know, but see no reason the garage would have removed the thermostat - that wouldn't have allowed them to drain the coolant. Cabin heat is approx in line with the gauge i.e. when on bottom stop the air is warm but not hot as it usually is when max heat selected and gauge on 90 C. When thermostats fail, do they always default to permanently open to prevent damage ?

I don't understand the comment about "thin oil" for A5/B5 , surely that is defined by the 5-30W viscosity ? Since my engine is a completely standard, lightly-loaded non turbo-charged petrol unit, is it likely any of the elements you mention could be harmful ? Forgive me if I'm asking too much there.

 

[Burnerman]

As I see it, the A5 / B5 oils are so much more specialised and can cope with the adverse affects of high ethanol content in petrol and bio additives in diesel - neither of which your car needs.
There have been many changes in the materials used for pistons and cylinders and these oils cope well with Nikasil type cylinder coatings - which obviously means that reboring isn’t possible.
For sure I can’t say if any of these would harm your engine for sure, but they would induce bore glazing which would see your oil consumption increase dramatically......often enough, very high output engines need a semi synthetic brew, but motors like the fragile Ford Ecoboost need their own formula, and high oil change intervals play a part too.
You are correct of course, that a 5/30 oil has that viscosity, but more expensive lubes keep that viscosity for much longer.

Long gone are the days when a specific diesel oil was needed for car Diesel engines in the mid eighties - basically they had so much detergent added to deal with the carbon produced by inefficient combustion.
Use that in a petrol car and the carbon was removed from the piston ring lands - so oil consumption rocketed!

Regarding the thermostat, they can fail either closed or open.....some are designed to fail open and they tend to be in the bottom hose. I can’t comment on yours!
On some engines, the ECU would be most unhappy and adjust the fuelling to suit a cold engine so it’s important that things get fixed.
John

 

[mointainwalker]

Thanks for your time and trouble , John . Are you taking the bike down into France/Switzerland this year ?

 

[Burnerman]

We’ve more or less decided to call it a day regarding our two wheel touring - advancing years and the desire for comfort etc! I’m still biking in Blighty though and intend to continue.
We’ll be heading for Grindelwald next year I hope, but I’m undecided whether to drive down ( the Hull / Zeebrugge ferry being no more ) or to fly to Geneva and hire from there.....I’m still rather spooked by Covid, but are chancing a flight to Beziers this summer which may recover my confidence!
Regards
John

 

[daviesm1976]

I used to have a Vectra c with this engine.

The thermostat is very accessible and easy to change. The housing is plastic and the bolts only need 8Nm so use a small torque wrench

The temperature guage is a false reading as a rule. On a Vectra c the thermostat opens at around 95 and the fan doesn't kick in until 105.
You can monitor this with a diagnostic mode. I can no longer recall the sequence for activating this but it's an easy Google.

The coolant system is self bleeding so if you think you have an airlock just take the lid off the coolant reservoir cold and run up to temperature.

The Vectra thermostats fail open normally so engine cools on an open road at higher speeds but heats up in traffic/when working hard. Check the hose from the thermostat to the radiator when you start the engine in the morning. If it starts to warm up straight away you know it's stuck open.