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Discussion Starter · #1 ·
Hi there, Newby here, as per the title, what is involved and how long could it take to replace the radiator that is badly blocked and the engine is overheating.
Thanks in advance
 

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Discussion Starter · #2 ·
Just to let you know I have carried out all other diagnoses, and had replaced new water pump, new Thermostat mounted on the top front of the water pump housing, had HG litmus test - no issues with HG, when engine is nearly at boiling point, fans kick in but blows only cold air so indicating coolant is not flowing through the main radiator, problem developed this summer so we did not know that internal heater Matrix may also be blocked, as absolutely no heating in the cabin, but today I took the internal Matrix out and had it flushed and cleaned refitted, bled the coolant, started the engine, brilliant amount of cabin heat, but engine overheated and pushed all the coolant out such that water pump has no coolant to pump so the internal matrix stopped producing hot air in the cabin.

I got a new radiator, it is now a matter of replacing it, I need some ideas how difficult a job this could be and any pointers to any old threads how it is done will be really helpful. Thanks
 

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Discussion Starter · #4 ·
When the engine is up to remperature are all hoses hot?
Yes they are all boiling hot to touch all the way up to the rad, and even those which goes to a plated heat exchanger for auto transmission, except the two which goes to the internal Matrix, but after I removed the internal Matrix and refitted it they were still cold, so had to remove the hose from the water pump side and fill it up with a water hose until water started to flow out from the reservoir, whilst the hose from the pump was out we temporarily blocked pump outlet, to fill up the internal matrix, once bled, the cabin heated so well, really heated it well, but then the engine temp rose and water started to boil out of the reservoir quite a lot of it, emptying the contents and now as all the water (coolant) is out so the internal matrix stopped giving heat. Radiator fans were on as well, so definitely blocked radiator.
 

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Not done it on a corsa myself but not normally a big job to replace, especially on cars with smaller engines. Harder on the diesel engine I believe because turbo gives less access and additional pipes going to intercooler, but not sure what engine you have. If you hadn’t got a new rad already I’d have suggested to disconnect the hoses from the rad, leave the rad in place, and stick a hosepipe in the outlet to back flush it. Might be worth doing anyway just to confirm if the rad is blocked.
 

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Discussion Starter · #7 ·
Thanks mate, I have been putting it off even though I have had a new rad ordered from an ebay supplier for under £50, Today experimented with fans not cutting in till after the water starts oozing out of the reservoir bottle, which is what causes overheating issues as the fan seems to cut in pretty late like 90+ degrees, knowing a bit about electronics and thermistors, they use an NTC sensor, meaning its resistance decreases when engine gets hot, so I tricked the ECU with a 1K ohm resistor in parallel, its the ECU which determines through firmware when the fan relays kick in as there is no temperature sensor switch on the radiator which can alternatively kick the fans On independent of ECU. So this trick does work, fans do kick in earlier, slow speed fan first and it never heated enough to kick in High speed fan despite running the engine on idle or around 1000RPM on a slight load, (headlights ON, car in D with handbrake and footbrake on at around 1100RPM. OBDII plugged in to see real time data stream indicated engine coolant temperature never rose above 75C, internal heating working fine giving out moderate heat.

Slight unexplained misfire occurring every few seconds, no fault codes, so i suspected that my resistor might be something to do with it, removed the resistor and the misfire continued, so it was not the resistor causing the problem, cleared out any fault codes still the misfire was apparent, any way it took only less than 5 minutes after I removed the resistor for the engine to reach 93C from about 80C and water started to spew out, as the fan had seized to come on earlier as the resistor was removed, so this is why the fan never kicked in even at 93C and engine started to boil dejecting coolant, which in turn would create low water level and stop pump circulating water as it would just spin dry, and internal heating stops working.

Having said this I also put a radiator cleaning agent in the coolant which somehow seems to unclog blockage (Arial washing pod) which seems to work brilliant and opens up blockages, so at the moment I am getting by without having to change the radiator, as long as fans cut in good time before engine gets too hot, i.e. at around 80C.

One disadvantage of adding a resistor to engine temperature sensor to trick the ECU is cold starting, because ECU thinks the engine is warm, or hot, so it does not inject extra fuel for cold starting so requires a good few extra cranking and fuel pedal depressed when starting.

It may well be possible that I have been given a wrong type of temperature sensor. My apologise for the long read.
 

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Good to hear you’re finding results. Don’t let it be a red herring though, during the winter in normal driving then the fans should hardly ever kick in unless stuck in heavy traffic. If the car is still overheating during normal driving and heat isn’t getting to the inside heater matrix then core issue still sounds like water circulation / blockage.
 

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, Today experimented with fans not cutting in till after the water starts oozing out of the reservoir bottle, which is what causes overheating issues as the fan seems to cut in pretty late like 90+
The fans on these generally cut in at 105c (lots of threads about it here) if you are getting boiling coolant at 90c something is wrong.
 

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Discussion Starter · #10 ·
Thanks Tommy, I am hoping that I can avoid replacing that rad, it would save me tons of work in removal and refitting the new one, I would definitely try opening the hoses to the rad to flush it out with a water hose provided I can get to hose clips easily with a strong jet flow of water, I agree in this cold weather fans should rarely come on except in traffic, that is one reason I let it idle or ran it under part load in Drive and with handbrake and foot brake on at no more than 1100rpm, so as to cause it to heat up whilst parked, as idling without any load; it never crossed 75C, as the slow speed fan had cut in. Sorry I did not observe at what temperature the fan kicked in with the resistor but definitely much sooner, this is with that 1K resistor across the two wires to the thermal sensor on water pump housing .The concentrated Arial soap pod does work pretty well each time but the effect lasts only week or so. Perhaps I need to drain my coolant all out when it has dissolved any rubbish and hot then refill with fresh anti-freez mixture.

Super Moderator, thanks as well, yes it does seem Vauxhall Corsa are running their engines pretty hot compared to other manufacturers. 105C under pressure, whilst I was running it without the cap so under atmospheric pressure, and my OBDII plug in diagnostic tool was used to monitor engine temperature, which could have pockets of hotter and less hotter areas around the engine block causing water to gush out. HG had been tested twice for combustion products in the coolant and indicated no issues.
 

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Discussion Starter · #12 ·
Buy yourself a new coolant tank cap. It is probably not holding the pressure sufficiently, causing the coolant to boil at a lower temperature.
Had two caps replaced as this was suggested by someone earlier and it made no difference to overheating and loosing coolant, most people suggested HG gone, but this was litmus tested twice at two different garages.

I now think that radiator is the culprit and when I put in Arial washing pod it loosens up whatever is inside and lasts about a week to 10 days and then as rad gets blocked up again, fans cut in late, too late to prevent adequate cooling.
For now the pod has done its job, tomorrow I will drain the entire coolant from the rad and refill with fresh coolant and another pod and warm engine up, drain again, let any dissolved matter get drained out, this should improve rad efficiency and run cooler, and I will try to add a different value resistor as 1 K may be too low as it may be bringing fan on too early, so trial and error and use may be 1.5K, or 1.8K or even 2.2K to see what gives me best operation where by fan kicks in at around 85C
 

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No offence here at all and I’ll happily shush if opinion isn’t wanted, but I think you’re chasing a rabbit down the wrong tunnel, so to speak. I personally don’t think the fans are the issue and if not careful you may end up with a potentially blocked rad and burnt out fans.
 

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Discussion Starter · #14 ·
No offence taken mate, I do value any constructive opinion, yes this is the case, naturally we first explored the easier to reach tunnels so to speak, but the rabbit was not there, having gone through all the tunnels except the hardest one, so sure that is where the rabbit must be, so we are going to get to it in the end, but as this is the hardest tunnel, I was trying to see if there is an easier way to get to it, so the blockage in the radiator could be cleared off permanently using proprietary radiator flushing chemicals, if this works well and good, if not then we will have to dig out the last tunnel, strip the front end of the car and replace the rad, it is not an easy option when we may have a few tricks up our sleeve , so I was trying to see other ways, and yes there appears to be some success, it may not be the right way, it is an old car not worth much, I was almost going to dump it when I was told that it needs a new HG, so I was not going to spend tons of money on having HG replaced, only to find that it was not what was the issue, so far I have not done any more on it yesterday or today due to Christmas, so when I used that Arial soap pod, rad got cleared, or unblocked, I ran the engine for at least over half an hour and the temperature never rose above 80C. It may not be the ideal temperature this engine was designed to operate at.

Yes I understand if all was perfect, the coolant is designed to operate at 105C so that means there should be no pressure leaks anywhere, in the filler cap or from any other place including HG .
 

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, I ran the engine for at least over half an hour and the temperature never rose above 80C. It may not be the ideal temperature this engine was designed to operate at.
You said earlier you changed the

new water pump, new Thermostat mounted on the top front of the water pump housing,

so there is no reason it should be running at 80c these engines are known for running around 105c as mine does.
 

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Discussion Starter · #16 ·
You said earlier you changed the




so there is no reason it should be running at 80c these engines are known for running around 105c as mine does.
Yes, SXI 1.2 Just to confirm, my Corsa is 1.4, I know another mate who has a similar age Corsa and his one also runs quite hot, one summer he could feel and smell his engine as overheating, but it was not as they run at 105C.

Yes so I will have to now tackle replacing the radiator, no other option mate.
 

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Discussion Starter · #18 · (Edited)
If the radiator was blocked or partially blocked it would run hotter not cooler than the normal temperature of 105c how can it run at 80c with a blocked radiator?
This whole thread makes no sense to me whatsoever.
Just to reiterate, car developed overheating problem, using a lot of water over a few miles journey, showed it to many experts, two opinions pointed to its HG, but litmus test was Ok, so another said try new rad cap, so two new caps were tried, they did not make any difference, so one said remove its thermostat from the housing, this was done, car still overheated, so one expert said coolant is not flowing, he made that point on the bases that my internal heater matrix did not heat up the cabin either, so flow problem and pointed to a water pump issues, so this was replaced, the old one was perfect in fact, fans cut in very late so one opined that Temperature sensor may be at fault, so this was replaced with a new one, again it made no difference, so finally there was only one more thing left to suspect and it was a blocked radiator, it was diagnosed as blocked rad, this is when I ordered a new rad, but has not been replaced yet.

So instead I thought what is the harm if I try and clear up blockage in the rad by using what was available readily...Arial concentrated washing machine pods, what harm could it do? it is suitable for washing machines with aluminium parts so what harm can it do in a car? no harm in trying it since if it does not work I have got a new rad ay way, so from this point on I tried experimenting further to see if I can achieve cooling without removing or replacing the rad.

So I think you missed something, what I did was as an experiment and to buy some time, i.e. temporary fix the problem, first by using Arial Concentrated liquid detergent meant for washing machines, this definitely helped cleaning the radiator obstruction, may be not fully but adequately, then also by adding a 1kilo Ohm resistor across the Temperature sensor, which in cold state is around 1.6K and its resistance starts to decrease as the engine starts getting hotter and hotter, so when its resistance drops down to a very low ohms like less than 200 ohms, this is when the fan kicks in, and by this time the engine is already boiling hot and spewing coolant out.

So by adding a 1K ohm resistance your new resistance now becomes 1.6K ohms in parallel with 1 k ohm will give you a cold engine resistance of about 615 ohms, so you have a head start, meaning the ECU thinks the engine is already warm, possibly like 50c to 60c, when in actual fact it is still cold, such that when engine actually reaches 80c, the overall resistance is now just under 200 ohms and the fan kicks in and coolant starts to cool down by the fan, never reaching above 85c, so preventing it from boiling over with just the low speed fan running, but if the car was under load, then engine would build more heat and so it would then kick in high speed fan as temperature continues to increase and the overall resistance continues to decrease, when the engine cools down the resistance climbs up and fans shut off.

This trick did work for me, but but are there any consequences of running an engine at 85c as opposed to running it at 105c , I don't know, unless it effects its emissions control inn some way, only know when it is due for its next MOT

But as soon as I take that 1K resistor out, engine boiles over, coolant started to spew out.

Under normal idle conditions the engine is never in much load as it idles at around 850RPM, and in normal driving conditions the radiator is dissipating heat without the fan being required due to natural air flowing through the front grill when a car is in motion. So if this trick works for me I then do not really have to replace the radiator even if I said it is a temporary solution, all depends on its next MOT, if it fails on emissions it may mean the engine needs to run hotter then I will then have to replace it nevertheless and remove the external 1K ohm resistor I added.

I would have changed the radiator if it was easy without having to strip half the front of my car.
 

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That’s fair enough. For awareness the front bumper is actually really easy to get off, I took mine off yesterday in about 15 minutes. A few torx screws on the slam panel, a few underneath, and one in each wheel well that holds the top corner to the arch.
 

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Discussion Starter · #20 ·
That’s fair enough. For awareness the front bumper is actually really easy to get off, I took mine off yesterday in about 15 minutes. A few torx screws on the slam panel, a few underneath, and one in each wheel well that holds the top corner to the arch.
This is what I had been waiting for, any information on what is involved, any complications etc that I may have to watch out for, and I tried to search on You Tube for any videos but there was nothing on this, yes I might as well do this properly, instead of messing about with resistors and soap pods, get it done for once and all.
many thanks
 
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