Head gasket/Bad water pump/Thermostat??

Head gasket/Bad water pump/Thermostat??

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Discussion

IntriguedUser

Original Poster:

988 posts

120 months

Wednesday 29th July 2015
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Corsa C 1.8 (Z18XE)

Car has been over-heating recently, usually sits on 90 degrees, dipping to 87/88 when moving at motorway speeds with nice cold air. However it has since been sitting at 94/95 with the heaters on the top setting, and driving at anything more than 6/10 for a minute or so will put it up to around 97 + and it takes ages to come back down.

- There's no leaks, none coming from the weep hole on the water-pump or any hoses/radiator.
- There's no coolant loss at all

It does need a waterpump/timing belt change anyway, so I'll get that done regardless, maybe the fin(s) on the waterpump have worn or broken?

Could it be the thermostat?

I did think my head-gasket could be going, how common is it for a HG failure when the only symptom is over-heating, no oil in coolant/mayo on oil cap and so on?

I guess I should get my local indie to do a compression test, but do you have any suggestions on what I should be trying to eliminate?

Kind regards,

IntriguedUser

GavinPearson

5,715 posts

250 months

Wednesday 29th July 2015
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Generally. ......
If you get heat in the cabin the water pump is working.
It is most likely a thermostat.

IntriguedUser

Original Poster:

988 posts

120 months

Wednesday 29th July 2015
quotequote all
GavinPearson said:
Generally. ......
If you get heat in the cabin the water pump is working.
It is most likely a thermostat.
Ha, I get more than heat in the cabin! Bloody getting burnt

I wonder how much thermostats are, ECP shopping time.

Thanks.

JayMawds1982

24 posts

118 months

Wednesday 29th July 2015
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Buy a Vauxhall thermostat. Aftermarket thermostats aren't worth it/

B'stard Child

28,322 posts

245 months

Wednesday 29th July 2015
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JayMawds1982 said:
Buy a Vauxhall thermostat. Aftermarket thermostats aren't worth it/
I agree I've found that in the past

gp3000000

103 posts

133 months

Thursday 30th July 2015
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97 isn't overheating. Many modern cars the first speed fan doesn't come on until 112/115. Remember, pure water in your cooling system under normal operating pressure doesn't boil until 120+. Coolant mixed in the correct proportions, and you're on your way to 140 before boiling.

Sounds like normal operation to me

B'stard Child

28,322 posts

245 months

Thursday 30th July 2015
quotequote all
gp3000000 said:
97 isn't overheating. Many modern cars the first speed fan doesn't come on until 112/115. Remember, pure water in your cooling system under normal operating pressure doesn't boil until 120+. Coolant mixed in the correct proportions, and you're on your way to 140 before boiling.

Sounds like normal operation to me
Doesn't sound at all normal to me.

If the car has consistently run at 90 deg up to now then I think I'd want to investigate why it's now running at 97 and taking some time to come back down.

If a car returns 35 mpg all the time and then drops to 30 mpg for no apparent reason I'd want to investigate that too

996TT02

3,308 posts

139 months

Thursday 30th July 2015
quotequote all
Something to consider.

Many modern cars have "damped" temperature gauges.

In other words, within a wide range of temperature that is considered safe and normal, the gauge or temp readout just sits in the middle.

It will only rise if the temperature goes outside the "safe" range.

This to allay concerns about overheating etc and subsequent hassle.

Could potentially be that your damping has gone and the true temperature is being displayed, as it varies.

TwistingMyMelon

6,385 posts

204 months

Thursday 30th July 2015
quotequote all
Change the thermo for genuine VX one.
Put the correct spec coolant in
Check for leaks/holes or issues


Ensure all basics are covered before worrying about HG


gp3000000

103 posts

133 months

Thursday 30th July 2015
quotequote all
You would have to spend a lot of time... The reason could be literally anything - from a radiator not cooling as efficiently as it used to to a thermostat opening slightly less than it should.

Until the fan, running continuously, cannot keep the temperature at 90, it's operating within it's design characteristics, and won't pose a problem.

B'stard Child

28,322 posts

245 months

Thursday 30th July 2015
quotequote all
gp3000000 said:
You would have to spend a lot of time... The reason could be literally anything - from a radiator not cooling as efficiently as it used to to a thermostat opening slightly less than it should.

Until the fan, running continuously, cannot keep the temperature at 90, it's operating within it's design characteristics, and won't pose a problem.
Read the OP

original poster said:
With the heaters on the top setting
One way of getting an engine with cooling issues to cool down is put the heater on full blast - it's very effective as an additional way of dropping the temp

But I'm sure that's all within the design capability surely wink

I would wonder if the electric fan is even running at all??

Mr Tidy

22,065 posts

126 months

Thursday 30th July 2015
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Exactly what was said above - when it gets hot see if the electric fan is running.

It could be nothing worse than a failed temperature sensor - I've had to replace a few of these in the past.

morgrp

4,128 posts

197 months

Thursday 30th July 2015
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Stick a genuine stat in it - HG failure or water pump would see a drop in coolant

morgrp

4,128 posts

197 months

Thursday 30th July 2015
quotequote all
Stick a genuine stat in it - HG failure or water pump would see a drop in coolant

IntriguedUser

Original Poster:

988 posts

120 months

Friday 31st July 2015
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Just purchased a Circoli thermostat from ECP.

Haven't had it fitted yet, should I just return it? Heard some horror stories from these brands on ECP on other forums. I believe the genuine VX one comes with a coolant temp sensor too, I'll investigate.

The fan does come on at 92 degrees, and goes up a level at 97 ish. I did some research and the coolant isn't circulating through the coolant top up place when the fan is on, which leads me to believe the STAT is stuck in the closed position. Lower radiator hose is also cold.

I'd just like to add that this definitely isn't normal, I've owned two 1.8's and done a combination of nearly 45,000 in both (How an earth I don't know) and I know exactly when something isn't right. I thought water boiled at 100 degrees, what makes the process different in the cooling system?










Edited by IntriguedUser on Friday 31st July 03:13

normalbloke

7,401 posts

218 months

Friday 31st July 2015
quotequote all
IntriguedUser said:
Just purchased a Circoli thermostat from ECP.

Haven't had it fitted yet, should I just return it? Heard some horror stories from these brands on ECP on other forums. I believe the genuine VX one comes with a coolant temp sensor too, I'll investigate.

The fan does come on at 92 degrees, and goes up a level at 97 ish. I did some research and the coolant isn't circulating through the coolant top up place when the fan is on, which leads me to believe the STAT is stuck in the closed position. Lower radiator hose is also cold.

I'd just like to add that this definitely isn't normal, I've owned two 1.8's and done a combination of nearly 45,000 in both (How an earth I don't know) and I know exactly when something isn't right. I thought water boiled at 100 degrees, what makes the process different in the cooling system?
.
Edited by IntriguedUser on Friday 31st July 03:13
The boiling point of water increases as it is put under pressure. It's just over one degree C per psi above atmospheric.



Edited by normalbloke on Friday 31st July 13:42

B'stard Child

28,322 posts

245 months

Friday 31st July 2015
quotequote all
IntriguedUser said:
I'd just like to add that this definitely isn't normal, I've owned two 1.8's and done a combination of nearly 45,000 in both (How an earth I don't know) and I know exactly when something isn't right.
Good - I was worried that you would be easily convinced to ignore the issue

IntriguedUser said:
I thought water boiled at 100 degrees, what makes the process different in the cooling system?
Pressure in the system - like a pressure cooker

Addition of Antifreeze to the water

csd19

2,170 posts

116 months

Friday 31st July 2015
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How old is the car - any chance you could be looking at a partially blocked rad (if it's on the original)in addition to the stat issue?

red_slr

17,122 posts

188 months

Friday 31st July 2015
quotequote all
Had a blocked rad on a vehicle last year. Replaced the water pump and stat and it was still overheating but only at low speed.
Took the rad out (PITA) and it was so crammed with dust and debris that it had to be replaced.

That said on cars its generally not a problem unless you live down a farm track etc...

If it was HGF you would, in general, see a lot of pressure build up plus oil gets into the water.
HGF can also cause a lot of steam from exhaust.

At this time of year you could take the stat out as a temp fix if you need to use the car. Would also prove the stat is the issue as your temps would return to normal (after a longer warm up time).

beko1987

1,636 posts

133 months

Friday 31st July 2015
quotequote all
i'd start with the stat. On 'er indoors (1.6 16v) meriva the temp needle didnt work at all, just stayed at the bottom, unless the car was stationary, then it would climb.

New (non genuine) stat cured it, and now it works as it should. I did do the cambelt and waterpump at the same time, but the old pump did work, so I think the stat did cure it.

The heaters were always hot, their hotter now. The rad fan kicks in now too, which it never did before, presumably because its sensor wasnt getting the right temp of coolant on it to kick it in.

I'd troubleshoot it by:

Coolant drain, flush (heater matrix, pull both pipes off engine bay side and fire the hose on low pressure in one side then the other)
Flush/check the rad
new thermostat
new coolant
damn good bleed
idle it/low revs until it's hot.

The 1.6 stat opens at 92 degrees, which is just over halfway on the gague. Needle goes to the middle, then 2mm more and the stat opens and the fan comes on, then the needle drops back down to the middle again