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Overheating, I am stumped

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24 Jan 2023 10:24 #247139 by johnna
Hi all, this is my first post here (although I have been lurking for a while), I have an overheating problem and cannot get it solved.My Jimny is a 2009 with an M18a engine. I have tried the following:1. New radiator cap (x2)2. New thermostat (x2)3. New heat sensor (x2)4. New radiator5. New condensor6. New water pump7. New head gaskit (although the old one was fine)8. New Visco9. Coolant system pressure test10. Cut new holes in the front bumper to allow more airflow (this helped a bit, but still too hot)11. Put washers on the bonnet mounts to lift the rear of the bonnet by 3mm to allow airflow.12. Replaced plugs (old ones were fine)In town the gauge is reading about 97c with the AC off, 105c with AC on (ambient temp 26c) on the highway I get 107c with the AC off.I am at my wits end, I don't know what else I can try to sort out the overheatAny suggestions?Thanks
PS Please excuse the ARB sticker on the bumper, it is not an ARB, just my daughter messing with me
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24 Jan 2023 10:33 #247141 by Lambert
Replied by Lambert on topic Overheating, I am stumped
Welcome to the forum. Hmm. When you replaced the head gasket did you have the head crack tested, it's not unheard of?

Temeraire (2018 quasar grey automatic)
One of the last 200ish of the gen3s, probably.
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24 Jan 2023 10:41 #247142 by johnna
Replied by johnna on topic Overheating, I am stumped
Thanks for the reply, we actually replaced the whole head when we did the head gaskit, granted it was a used head but it came off an engine with no problems

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24 Jan 2023 11:40 #247144 by saxj
Replied by saxj on topic Overheating, I am stumped
A few of the guys on our whatsapp group have solved overheating issues on their M18's. There are some very knowledgable and helpful guys on the group. chat.whatsapp.com/L5GewnZgCij7UA8XnRe1vx

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24 Jan 2023 12:33 #247146 by johnna
Replied by johnna on topic Overheating, I am stumped
Awesome, thank you

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24 Jan 2023 16:36 #247153 by Roger Fairclough
You haven't mentioned the fan? If it is viscous, does it appear to be working? If it is electric is the thermo. switch operating and is the motor switching on? Was that bumper already on before your problems started, it may be partially blanking air to the rad.

Just a few thoughts.

Roger

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24 Jan 2023 17:09 #247154 by DrRobin
Replied by DrRobin on topic Overheating, I am stumped
When you put the A/C on you add a little bit of extra load to the drive the compressor, so that adds a bit of heat, but unless your A/C compressor is starting to seize it wouldn't make much difference.

The heat that the A/C takes out of the car is lost in the condenser which is in front of the radiator so reduces the efficiency of the radiator and that is usually why the engine runs hotter with the A/C on.

If you have a head gasket issue then you would normally see one of the following:

Oil or bubbles in the water;
Water vapour in the oil (or emulsifying);
One of the spark plugs wahed clean.

The fact that out on the highway it gets hotter suggests it might be airflow, I know the engine is working harder, but you should have airflow over the radiator and this should compensate.

So how long have you had the vehicle and what, if anything, changed when it started to over-heat?

It could also be mixture, if it was running very lean, that would cause it to over-heat.

Does the M18a engine normally run with a bigger radiator (someone from the forum might know)?

What about a build up of debris on the outside of the radiator or even a coolant flush (going on what you say you have probably already done this)?

Is the water pump belt slipping (any squeal?), giving poor circulation or is the water pump starting to sieze up (I see the water pump is new)?

If all this fails the specialised Whatsapp group might be your best bet.

2011 Blue Jimny SZ4 morphing in to a 2020 SZ5 in the next week or so.

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25 Jan 2023 07:54 - 25 Jan 2023 08:21 #247161 by Scimike
Replied by Scimike on topic Overheating, I am stumped
How does the M18 donor vehicle radiator compare to the standard Jimny 1.3 radiator in size and cores?

​​​​​​Has anyone checked to see if you simply need a larger capacity radiator to cope with the larger capacity engine?

It's just a Sherlock Holmes inspired question based on the fact you have changed everything. It may simply be the standard radiator operation is marginal on the M18 and some conversions are just about getting away with it. I don't know the answer unfortunately, but hope someone has the comparison information as I would also be interested.
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Last edit: 25 Jan 2023 08:21 by Scimike.

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25 Jan 2023 08:25 #247162 by johnna
Replied by johnna on topic Overheating, I am stumped
Thank you for your reply Roger. I replaced the Visco, referring to the viscous coupling for the fan, it appears to be working fine

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25 Jan 2023 08:43 #247163 by johnna
Replied by johnna on topic Overheating, I am stumped
Thank you for the comprehensive reply!

If you have a head gasket issue then you would normally see one of the following:
Oil or bubbles in the water;
Water vapour in the oil (or emulsifying);
One of the spark plugs wahed clean.

It displays none of these symptoms and we performed a chemical test that indicates that there are no gasses present in the radiator.

The fact that out on the highway it gets hotter suggests it might be airflow, I know the engine is working harder, but you should have airflow over the radiator and this should compensate.
That was my initial thinking, I then cut out allot of the replacement bumper. This did help quite a bit so there must have been an airflow problem of sorts. I can't cut away any more of the bumper without risking structural failure of the bumper

So how long have you had the vehicle and what, if anything, changed when it started to over-heat?
I have had it for a few years. The problem started when I upgraded the engine from 1300 to 1600. After being unable to solve the issue we put in an 1800 as we thought there my have been an issue with the oil pumping system.

It could also be mixture, if it was running very lean, that would cause it to over-heat.
Is there any way to adjust this as this? I was under the assumption that the ecu does this automatically

Does the M18a engine normally run with a bigger radiator (someone from the forum might know)?
According to what I have read they use the same radiator, but would love to hear from those in the know

What about a build up of debris on the outside of the radiator or even a coolant flush (going on what you say you have probably already done this)?
Yes this was checked, as I say the radiator and condenser are brand new,

Is the water pump belt slipping (any squeal?), giving poor circulation or is the water pump starting to sieze up (I see the water pump is new)?
Yes, waterpump was replaced, I haven't noticed any belt slippage.
 

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25 Jan 2023 08:48 #247164 by johnna
Replied by johnna on topic Overheating, I am stumped
Thanks for your reply!

How does the M18 donor vehicle radiator compare to the standard Jimny 1.3 radiator in size and cores?
The local guys here have done a few of these upgrades and always used the standard radiator without an issue. I would love to hear if there is a radiator upgrade, that may solve the issue,

​​​​​​Has anyone checked to see if you simply need a larger capacity radiator to cope with the larger capacity engine?

It's just a Sherlock Holmes inspired question based on the fact you have changed everything. It may simply be the standard radiator operation is marginal on the M18 and some conversions are just about getting away with it. I don't know the answer unfortunately, but hope someone has the comparison information as I would also be interested.
Thanks, yes I actually hope there is an upgrade radiator that can fit. Think it may help

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25 Jan 2023 13:37 #247165 by DrRobin
Replied by DrRobin on topic Overheating, I am stumped
Don't get me wrong, it looks like radiator and airflow to me, but there could be other issues.

'It could also be mixture, if it was running very lean, that would cause it to over-heat.
Is there any way to adjust this as this? I was under the assumption that the ecu does this automatically'

The ecu does do set the mixture, but bases this on
- 'maps' of how much fuel/air is required for a certain rpm
- the MAF sensor (how much air is entering);
- all fine tuned by the O2 sensors.

In theory the bigger engine will take more air for any given rpm and therefore need more fuel, but the 1.3 stock ecu might have 'maps' which are fine tuned for the 1.3 and these need to get over-written, this usually happens over a few hours of driving. I am not sure if others have changed the ecu when changing the engine or even if it is required but the stock ecu might not be able to cope well with the bigger engine.

What about timing? If you have pre-ignition that can cause over-heating?

2011 Blue Jimny SZ4 morphing in to a 2020 SZ5 in the next week or so.

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