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Rotara
Member Since: 02 Mar 2021
Location: UK
Posts: 59
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| Overheating on Higher Speed Journeys |
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Hi Everyone,
Recently I had a garage replace my expansion tank, at the same time I had the hoses and thermostat (complete assembly) replaced. The mechanic flushed the system twice and refilled the entire system with fresh coolant. Ran it for a couple of weeks, nothing major, short journeys and everything was fine. I watched the mechanic bleed the system and all looked pretty ok.
That is until my first high-speed journey. Coming off a 20 minute run around the M25 I noticed the temp gauge flicker between normal and high, then very quickly went to the top. The engine overheating warning light came on and I suddenly lost power. Luckily I was somewhere I could pull over. Waited half an hour, switched the heaters on full and waited for things to cool. I started it up and managed to get home.
Took the car to a different Land Rover garage where they hooked it up to their diagnostics. Nothing serious, a few general fault codes, they downloaded the latest transmission software, took it for a local test and everything felt and looked fine. In fact the car felt really nice and responsive.
Then today went on the motorway, again same thing happened. After about 15mins at high speed the engine temp increased and the car lost power. No throttle response and I managed to nurse it to a layby where I let it cool down.
After limping home and letting it cool down again, everything seems ok again. I checked the hoses, everything looks ok. Checked the expansion tank, fluid is bright pink & clean no traces of oil. Opened the engine oil cap, no frothing or 'mayonnaising', so no traces of coolant in the oil.
I'm just wondering if the new thermostat could be faulty? How would I know?
And would that be responsible for the sudden loss of engine performance (no throttle response)?
Any ideas about what else I can do before spending hundreds more on the mechanic taking out the entire coolant system?
Many Thanks.
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 28th May 2022 7:22 pm |
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lynalldiscovery
Member Since: 22 Dec 2009
Location: Maidstone
Posts: 7274
 
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I have had a new stat faulty from the box, this was on a 200tdi engine, and they take some getting hot, but she got hot alright!
Simple question, did it overheat before? if no then you have a fault obviously! so its either the stat u/s or the mech has maybe piped it up wrong if that is even possible, are all the hoses straight and not kinked? as its is quite congested down under the radiator.
Last edited by lynalldiscovery on 29th May 2022 8:04 am. Edited 1 time in total
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| 28th May 2022 9:29 pm |
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Matty 2332
Member Since: 02 Dec 2008
Location: West Yorkshire
Posts: 670
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Does it feel physically hot / any physical signs of it overheating? Could it be the temperature sensor that's faulty? if it is, and telling the vehicle its overheating, then it will drop into limp mode.
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| 29th May 2022 7:08 am |
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Rotara
Member Since: 02 Mar 2021
Location: UK
Posts: 59
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Thanks for your replies. I did a bit more investigating today and discovered the top of the engine gets really hot (top pipe going to top of the rad and across into expansion tank), whilst the bottom pipe (from lower part of the thermostat housing back into the engine block) is cold. This suggests to me the thermostat is not opening. I will attempt at replacing this during the jubilee bank holiday. I’m ok for short journeys until the engine warms up. Then it goes into some sort of performance limiting mode, as power is noticeably affected after driving for about 30 mins.
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| 29th May 2022 6:48 pm |
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Rotara
Member Since: 02 Mar 2021
Location: UK
Posts: 59
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Guys, I just had a call from the garage ahead of my car going in to them tomorrow for a thermostat replacement.
They were asking if I was sure it was not a failure of the viscous fan unit. They said a fan clutch failure wouldn't necessarily show up as a fault on system diagnostics, as it would either be stuck in the engaged or disengaged position. Given that I'm experiencing overheating if it was a faulty fan clutch I would assume it's stuck in the dis-engaged position (if that's the problem).
How would I go about testing the fan? Any ideas? Thanks.
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| 31st May 2022 4:33 pm |
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Bungle
Member Since: 07 Apr 2015
Location: Wanborough
Posts: 254
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Unlikely to be the fan if you are getting overheating at speed. Generally fan faults cause overheating in traffic where there is no airflow through the radiator, at speed there is normally more than enough air so the fan won't cut in anyway.
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| 31st May 2022 5:00 pm |
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Rotara
Member Since: 02 Mar 2021
Location: UK
Posts: 59
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I'm really at a loss with this.
I will take it step by step. Tomorrow is thermostat replacement with closer inspection of the rad pack and associated pipes and general coolant flow. Some have already said it might be an air pocket somewhere in the system. Well, hopefully, this will sort it. I'm still getting immense heat coming through the cabin heating matrix (which is probably understandable), but have no idea what impact the viscous fan is having. Some months ago it would come on at cold temperatures with a loud 'whoosh' sound and then cut out for no reason, even on cold start-up. Some folks have said it's symptomatic of a fan on its way out. Maybe it has packed in totally. but like what @bungle says it probably doesn't explain high speed overheating.
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| 31st May 2022 6:10 pm |
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Bungle
Member Since: 07 Apr 2015
Location: Wanborough
Posts: 254
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Just realised another part of your post states that the hose at the top of the radiator is hot and the one at the bottom is cold, this again suggests the fan is not the problem. The fan is used to boost the cooling power of the radiator so if the pipe at the bottom is cold then the fan isn't needed at that point. So either the water isn't flowing (or isn't flowing fast enough) through the radiator (faulty stat) or you have a fault somewhere else (possibly an air lock).
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| 1st Jun 2022 9:53 am |
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Rotara
Member Since: 02 Mar 2021
Location: UK
Posts: 59
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update - At the land rover garage this morning. carried out various tests. Head gasket test (with the blue fluid) - passed. Then ran diagnostics - passed, no errors. Tested the viscous fan by running the car with AC full on, revving engine hard - passed. They are now going to replace the thermostat. I bought an original LR one with 15 litres of fresh coolant. Hopefully, that will sort it out! Will report back.
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| 1st Jun 2022 10:24 am |
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lynalldiscovery
Member Since: 22 Dec 2009
Location: Maidstone
Posts: 7274
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If it is the stat at fault, please post the make of the faulty one so we can avoid it, as can later searchers.
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| 1st Jun 2022 3:02 pm |
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M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8102
  
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My guess the system has not gone through the anti-air lock procedure, it is quite involved and you have simply got air in the coolant system.
This situation has come up several times in the past, use the search facility located in the heading of the title page of this site, I have posted the procedure many times in the past  It can when others can't,
It will when others won't,
It goes where others don't.
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| 2nd Jun 2022 2:54 pm |
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Rotara
Member Since: 02 Mar 2021
Location: UK
Posts: 59
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Ok guys. The problem seems to have been resolved. But the garage was not able to pinpoint the exact cause, but this is what they did;
1. Ran a check on the viscous fan / passed.
2. Carried out a combustion check (for blown head gasket) / passed.
3. Replaced thermostat with brand new LR one / old one (LR original) was not tested as garage said the problem could be intermittent.
4. Flushed system & replaced with fresh coolant, bled system thoroughly and carried out a pressure test / passed.
5. Removed water pump, inspected function & condition / passed.
6. Cleared system faults rerun diagnostics = MAF sensor error / DPF full warning appeared.
7. Removed intake assembly, cleaned intake tubes, MAF sensors and throttle body sensor, checked and adjusted air intake flap inside the throttle body, cleaned everything and replaced, reset with diagnostics tool.
8. Added injector / DPF cleaner to fuel tank and ran vehicle stationery for 1 hour with diagnostics tool giving live data. No faults except DPF full warning (26gsm of soot build-up).
9. They gave me a diagnostics tool and explained how to do a forced DPF regeneration and gave me the option to go on a motorway drive for an hour or one of their technicians could do it and I’ll be charged the extra hour of labour - so I did it.
10. Took the vehicle on a long drive, carried out forced regeneration of the DPF as instructed / success (now only 5.25gsm of soot).
Returned to the garage, they gave a full inspection and recommended an early oil change as the overheating would’ve reduced the life and effectiveness of the oil. They said it was ok to drive still but just a recommendation given the fragility of the SDV6 unit.
They also carried out a general inspection of the vehicle and highlighted a few things to keep an eye on.
So far no overheating and the fluid level is spot on.
Hope this helps others.!
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| 6th Jun 2022 10:38 pm |
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Rotara
Member Since: 02 Mar 2021
Location: UK
Posts: 59
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Now in the market for an IID Tool for ongoing diagnostics/maintenance. If anyone knows of someone selling one. 
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| 6th Jun 2022 10:41 pm |
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Rotara
Member Since: 02 Mar 2021
Location: UK
Posts: 59
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Hi guys, my overheating issue returned yesterday. Maybe it hadn't gone away, but I've now managed to narrow it down to the following:
Urban driving, no Aircon - Normal temp, no issues
Urban driving with Aircon - Normal temp, no issues
Motorway driving no Aircon - Normal temp, no issues
Motorway driving with Aircon - The engine gets hotter than usual, forces out the coolant from the top of the expansion tank then a low coolant warning comes on.
Any idea why this is happening?
Many Thanks.
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| 14th Aug 2022 1:44 pm |
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M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8102
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Aux belt slipping under load?-new belt and tensioner needed It can when others can't,
It will when others won't,
It goes where others don't.
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| 15th Aug 2022 8:48 am |
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