1. Home
  2. Car Maintenance
  3. Astra H running hot, and how not to top up coolant

Astra H running hot, and how not to top up coolant

Greetings all,

I've just acquired a 59 plate Astra H (1.6 petrol, manual).

It seems to be running hot but without a temperature gauge it's difficult to know what is normal and what is abnormal. The dealer (2nd hand back-street place) isn't bothered, as far as they are concerned, 'modern cars runs hotter than old ones'. This is total BS of course, modern cars have the same designed coolant range that cars had 20 years ago. There is only so much pressure that a plastic header tank can withstand. The main vauxhall agent says the normal coolant operating range is 85 to 95 centigrade, but what at what temperature should the cooling fan kick in ?, and what temperature is needed to illuminate the red warning light ?. How would I test the latter to make sure the bulb actually works ?. The coolant tank has two small bore pipes entering at the top and where they enter the tank, the underside of the tank top wall has an obvious black smudgy mark. Unfortunately there is a baffle preventing me getting my finger in the wipe some of it off. Could this be oil or disintegrating rubber/plastic ?. The dealer says this is normal, but my old Astra F never did this.

On the right hand side of the cylinder head just below tha cam cover and to the left of the thermostat block, I was measuring 102 centigrade and yet the cooling fan still had not kicked in. By this time there was an obvious 'hot plastic/rubber' smell in the area around the thermostat block, totally different to the usual normal engine temperature smell, so I abandoned the test and switched the engine off.

I suspect the thermostat is stuck partially open or doesn't open fully, so that heater works effectively but not enough water is being sent to the rad when it's at normal temperature. Any views on this ?.

Also, the dealer had filled up the header tank almost to the brim. I had to remove a fair bit to get the level down to midway between KALT/COL and full. When challenged, he was adamant that the correct way is to fill right up to brim and allow the expansion to eject the excess !!. This is the first time I have ever encountered anyone doing it this way. New cars don't leave the production line like this do they ??. Doing it this way would result in a vacuum forming as the engine cooled back down.

What coolant level do other people expect their *cold* engine to show ?. Just curious.

Reply to
Andrew
Loading thread data ...

As a priority I would give it a sniff test to see if the head gasket has failed.

Reply to
Mrcheerful

That's what I am trying to persuade my neighbour to do, but he will have to borrow the kit from a place he does car jobs for.

I suggested to the dealer from whom I bought the car that this would be a good starting point. Naturally he thinks it is a waste of time, and went down the usual route - 'I've got 30 years experience, I know everything, don't tell me anything, blah, blah, blah'.

If that is OK I think I will fit a new stat anyway, and compare the two at various temperatures before refitting.

Reply to
Andrew

Over-filling the header tank and letting the system find its own level by ejecting any surplus is perfectly normal. The high/low marks are just there to check it is ok after this has happened.

The engine management will have a CTS, so can usually give the temperature by using the correct software. And that temperature will have a wide range which is acceptable depending on conditions. No car stays exactly at the same running temperature.

If it isn't losing coolant, it's probably ok. Measuring 100C somewhere isn't unusual either - that's why the system is pressurized,to raise the boiling point of the coolant.

Reply to
Dave Plowman (News)

I have two neighbours who have over 100 years combined experience in the motor trade and neither think it is correct to fill the header tank right up. They both set the level about half and inch above the COLD line when the engine is cold. If you fill right up, you are relying on the coolant cap to release the pressure, which may be higher than the rest of the cooling system is designed for. Also when the engine cools down you will end up with a vacuum.

There is a bleed pipe, about 1/2 inch outside diameter coming from the top of the rad into the top of the header tank. Where this pipe connects to the header tank there is an obvious grey/black smudge and I can also see small black lumps and specks elsewhere in the header tank.

Additionally, where this pipe joins the rad, it is weeping, but what is coming out is oily and brownish. The dipstick oil is clean but looks like it is fairly fresh and no sludge under the filler cap (yet).

I have now discovered that the Astra H has some secret menus where the coolant temperature is displayed below the uncorrected outside temp, together with the vehicle velocity.

Reply to
Andrew

My phone is plugged into a wall socket marked 'BT' :-).

Garmin used to sell an OBDII device that connected to some versions of their Sat navs and that displayed all the engine parameters interleaved with sat nav data. Unfortunately it has been discontinued. It was useful because it had a short cable between the sender box and the 16-pin plug allowing it to be cliped up out of harms way. I am aware of the cheapo chinese clones that plug right in but on some cars this obstructs the drivers legs.

Reply to
Andrew

If that's an accurate version of what they've told you they're idiots.

Well, the very first thing to do is sort any leaks.

Reply to
Dave Plowman (News)
[...]

Even sadder if he has no kids...

Chris

Reply to
Chris Whelan

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.