Cold running car

Silent Shrill

Hi. Opel corsa 1ltr, 2002. Car was running at 80 deg, never went above it. I initially thought thermostat stuck open so replaced it. Now it will not go to the lowest temp on the gauge of 70. If I let it idle for 15 mins temp rises as it should and fan cuts in around 92-95, but as soon as I start driving temp falls to non-registering. The heater in the car is also cooky. The top, (demister), works ok, it is warm, but only gets hot when car idles and temp rises. Put the heater in floor mode and it's cold......it's weird.
No loss of water, no bleeding to do for air from water as it does this itself.
If you have any idea as to "what to do next"........I'm all ears.

Waterson

Perhaps your water pump is freewheeling. Not uncommon on Opel group cars. will be more prominent at higher revs. Does sound like a circulation issue provided the system has been run up and bled.

Silent Shrill

Thanks. I've never heard of a water pump "freewheeling". But seeing your answer made me think. There is a noise, (like a jet engine sound, only not as loud), coming from that area. I was informed by the po that it needed a belt tensioner as the bearing in it was going. It does not really increase the speed of the sound as I increase with revs, (it does, but not significantly). If it were the belt tensioner I would expect it to increase with revs, respectfully.
What exactly is "freewheeling"? in respect to the water pump. How would it make the water constantly below 70?
I'm asking because after 40 years of car/bike mechanics I've never heard of this.......but makes sense, (if explained in better detail). I googled it but drew a blank.
Thanks, Bill

Silent Shrill

Waterson wrote: »

Perhaps your water pump is freewheeling. Not uncommon on Opel group cars. will be more prominent at higher revs. Does sound like a circulation issue provided the system has been run up and bled.

Yep, just heard a corsa making the same noise on utube........it was the water pump
Damn diddly........I never knew a water pump could make the car run cooler. It can obviously make it overheat if not functioning correctly, and the symptoms are tapping sound/water leakage around pump. But hey......something learnt,.......and I bow to your assistance......many thanks.

Waterson

A waterpump impellor can freewheel when it separates from the shaft of the belt driven pulley. On the bad ones if you hold the impellor (the yoke that actually drives water around the system) with one hand you can move the belt.pulley independently with the other hand.

Silent Shrill

So I replaced the water pump today. The old one was good, it was not freewheeling but a little stiff instead, but still turning. Replaced the drivebelt as it was in pretty bad nick. And the result???........zero. It made no difference at all. It still stays below 70 on the gauge, but goes up if left to idle for about 15 mins until the fan kicks in and the thermostat opens. So that's a new thermostat, temp sender unit, and water pump.......with no effect. I'm convinced whoever put the head gasket on did something to cause this. (P.O. stated he had the head gasket replaced), WTF with??...a refrigerator unit.

Tea drinker

Yeah thought you had it sorted with the waterpump.... :-(
If the system is not overpressuring or overheating and spitting coolant... kinda goes against a bad head gasket.
Wrong headgasket blocking some holes? Maybe but kinda reaching now.
What about some hose connected back asswards?
Thermostat assways in?
See if you can get any air out of it when it's hot and turned off by squeeezing the pipes with some gloves on.

Irish Steve

Some diagnostics with a thermocouple based temperature sensor look like the next step, to see what the real temperatures are on the pipes to the heater, the thermostat body, and to check if there are any other coolant pipes going to somewhere like an oil cooler or manifold heater, it may be worth checking that all the pipes are correctly routed, and check what's happening with the thermostat, just in case the new replacement unit is faulty, or sticking partly open somehow. It is possible that the sensors are lying about the actual temperature, if you can, checking the actual temperature with an external device and using a computer to check the temperature level being reported by the engine management system via OBD will be worth doing.

As it's over cooling, I'd not spend too much time worrying about the head gasket, if it was something like a blocked gallery, it would be over heating, which is clearly not the case.

jca

I think you're over thinking this tbh. The new thermostat is stuck open allowing water from the engine to circulate through the radiator continuously, maybe you left a seal out when replacing it. I know one version of the Corsa had a rubber seal behind the thermostat that was easily dislodged when changing it, another version had a rubber ring around the outside which was a fecker to keep in place while trying to close the housing. I'd take another look at the thermostat if it was my car.

Silent Shrill

Thanks for the replies. Everything is fitted correctly, and the correct way round. Gaskets are not trapped or incorrectly fitted. It's a basic 1ltr 3 cylinder corsa. All hoses heat up within 5-7 minutes. Hot air flows from the heater in the same time. Water is circulating the whole way back to the reservoir bottle via the choke hose. Pressure builds up as it hisses when the cap is released. The car performs as it should, and achieves approx 60 mpg. When left to idle it goes to 92 and then the fan comes on for approx a minute. It's performing as it should, bar the cold temp when driving. It's a self bleed system. I do know the outlet hose on the heater was very cool when I started to repair the system, so I flushed the system on 2 separate occasions. I stuck a hose on the inlet end to try to force out any crud, but the water coming out was quite weak. After doing all the above and all the new parts mentioned earlier, the heater is better but the gauge still remains below 70. The head gasket was mentioned as I discovered from others, on car forums, that they are indeed fitted back to front by some twats, and cause cool running. I don't think that this is the case myself. The water pump incorporates the temp sender unit, hose to work choke, and thermostat, at the top of the pump. The return hose from heater is situated just below these, and the impeller just below that. I think the water from the outlet of heater is so poor, in quantity, that it is not touching the temp unit, but instead passing it, giving a low reading, because the hoses tell a different story. When idling the water from the choke to reservoir bottle is practically minimal and allows the water to fill up the area where the sender unit is, this giving the true reading....Normal. As soon as I can get out to the car, when it is not raining, I'm going to stick the hose on the heater hose again, and let it run until the other end is flowing fast. I think it's a simple case of blocked matrix causing the problem. I will let you all know if this was indeed the case.

Tea drinker

My own story... I used that 2 pack flush on my car last year, I get more heat out of it than ever. Wouldn't leave it in any longer than recommended, it's strong stuff
I had already replaced the thermostat as I got the "cool runnings dude!" when driving down big hills, these newish engines do minimal to non existent fueling on overrun so heat just gradualy reduces in the engine.... and if the radiator is doing a great job cooling that water going through a stuck thermo, there's soon no hot water for a fan.

Waterson

Sunds like youre definitely on the right track with the heater matrix potentially being blocked. You should have good flow through this to have heat in the cabin.

Silent Shrill

Problem sorted. I stuck the pressure washer into the heater matrix hose. A load of gunk which included the flusher liquid came out. I replaced the new thermostat with the old. Everything is now functioning as it should. I tested the new therm and it works as it should. So the problem lied within the heater being blocked, partially. Quite a bit of money spent replacing everything, but all is well now.
Thanks to all for advice & assistance.

doctorchopper

Silent Shrill wrote: »

Problem sorted. I stuck the pressure washer into the heater matrix hose. A load of gunk which included the flusher liquid came out. I replaced the new thermostat with the old. Everything is now functioning as it should. I tested the new therm and it works as it should. So the problem lied within the heater being blocked, partially. Quite a bit of money spent replacing everything, but all is well now.
Thanks to all for advice & assistance.

No harm replacing a water pump on a 15 year old car anyway, cheap insurance to prevent overheating incase of a fail