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Discussion Starter #1
Hey all.

I got stuck today in Maidstone, because of the bad crash on the M20, and subsequent traffic issues.

Whilst sitting with the engine idling, I noticed the temp gauge begin to rise, I also noticed this yesterday on the motorway, it get up to just the first white notch at the top, where the last quarter begins, and then slowly goes back down, but then it seems to go up and down constantly, always getting closer to the top qtr again, should I be worried.

Looking under the bonnet, I cannot see any obvious radiator cap, but can see up behind the battery there is a white tank, almost see through, is this where I check the radiator levels, if so its full to the top so I guess thats not the issue, if in deed there is an issue.
 

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Hi iam not that familiar with the lag 1 or how high the temp rises to when running so check when cold or cool to so see if there is any brown oily looking stuff in the the water tank by looking down into the tank and also screw off the oil filler cap and on the underside of this cap is there any brown looking crap.

When the car is running and then stopping in traffic is the fan coming on to cool the engine by the sounds of this it is.It may be that the car is pressurizing and the head gasket may be gone but do as i said first and if in doubt take it to a garage and ask for a compression test to be done.I have to stress this may not be the case but it sounds to me that the car is running very high to me but this may be normal?????
 

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Just for reference my Laguna 1 when upto optimum temp runs at the 1st notch past the halfway mark on the temp gauge so I don't think anything to worry about there.

The expansion tank is indeed behind the battery & is where you check the coolant level.
 

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Both my old dTi and my new 1.8 16 valve run at one notch above half way too....

The temperature gauge fluctuation is a bit more concerning,however.Does the heater go hot/cool in relation to the gauge?.It could be an electrical fault somewhere,but equally could be an airlock in the system somewhere.
 

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One possibility could be a faulty temperature gauge sensor?
These are located in the thermostat housing - bolted to the right hand side of the cylinder head (looking at engine from front of car). Just follow the top hose from your rad

You would have to partially drain the cooling system to gain access though.
 

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All newer cars run hot... it's something to do with emissions. I'd worry if the temp wasn't around the halfway mark constantly as the car would probably be running rich due to the ecu thinking the engine was in cold start mode.

As long as the fans cut in (at about the 3/4) and the temp comes down, it's normal.
 

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Have you bled the system out at all or had any work done on the cooling system recently?.

The temperature gauge should not fluctuate as you describe yours doing......
 

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Discussion Starter #9
WOW, all these replies, lol.

ok, this temp thing seemed to happen for a few days only, now everything appears to be back to normal. The fan does kick in to cool things down, and it does so very fast (cooling) there is no unsusal sound from the engine area, the water tank has only water in it, the oil cap is perfectly clean, and I have been monitoring the oil gauge that pops up on startup, when it loses 3 whole squares Im topping it up again.

It actually runs extremely well, turbo kick in at 2k revs, no black smoke other than extremely hard pulling away and even then its not black, and disperses fast. Idle sits nicely, no fluctuating at all.

Air con is gona be a ***** to figure out, but in general I actually ike the car alot, very nice to drive, and I cruise home at around 85 every night and no issues at all.

Its strange, though its only a 1.9dti, it has significantly more pull than I would have expected, not the same as the Volvo D5 engine, but not bad either, surprising.

I did consider having the ECU remapped to increaste its power, however at the cost involved, cant afford it, thought about a different filter perhaps to get a little more air into the engine, but am no expert.

Anyone got any suggestions on enhancing performace without breaking the bank (or having the wife kick my ass)
 

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I'm having similar problem with my Laguna temp gauge. The normal running temp used to be halfway on the gauge or just above but lately it is running at 3/4 position. When idling, temp creeps up and the fan kicks in OK but strangely though temp gauge then rises rapidly almost to the top and when the fan stops the gauge drops back to 3/4 position. I've changed the thermostat but it has not cured the problem. I can make the fan come on when the temp is rising but the fan not yet cut in, by switching the AC on. And the same thing happens!
 

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Hi Neogis,

Which model Lag have you got and how old is it.

If you post the details it might help diagnose the problem.
 

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probably the fan temp switch on the right of the radiator has failed, very common fault, if your getting very high readings after getting caught up in heavy traffic for some time.
keep a spare paper clip handy and use it to short the back of the connector to keep the fans running and the engine cool when you out and about until you get the switch replaced.
dealership prices £25
indy' suppliers £18


:d
 

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Thanks Planmeca & mord.
My laguna is 1999 2 lit 8Valve auto. Fan cuts in OK when the gauge is about 3/4 on the dial but why does the pointer move rather rapidly to almost to the top as soon as the fan cuts in and drops back when the fan stops? As I said when I switch the AC on before the fan has cut in, it brings the fan on and the same thing happens to the gauge. I suspect it sounds like a drain on the battery caused by the fan is causing this odd behaviour. This may be something to do with the voltage regulator that supplies the gauge? Any ideas?
 

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I see where you are coming from the the Voltage Reg theory but as far as I am aware the regulator is resonsible for voltage control on more than just the temp gauge.

Are any other panel instrument changing at the same time IE the fuel level?

Normally a voltage regulator will either go short circuit (no regulation so any reading is possible) or open circuit No readings at all.

Is anything else happening at the same time?

If the fan cuts in I think you can discount the rad switch.

It could be a water circulation problem and the gauge is actually indicating the temp that it see's.

I have had problems before with the water pump being very inefficient and not able to cope. When was this last changed?
 

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The car has done 104,000 miles so far and I have done 32,000 miles since I got it 3 years ago. I have not had the water pump changed and I do not see any evidence of it being changed when the cam belt was done at 60,000 miles by the previous owner. Since it is running at a higer temperature during normal driving conditions, you may well be right in suspecting the water pump. Do you think there is an air lock in the system? I have not noticed anything odd with other gauges. What puzzles me is that the gauge moves up rather quickly when the fan cuts in. If it is the actual reading, why would the temperature change so rapidly? I will try to monitor the temperature using a strapped on probe of a meter I bought some years ago and see if I can detect anything. I'll post my findings when I've done that. Thanks for your suggestion about a faulty water pump - it may well be the culprit and if it is I will have it changed when the cam belt is done next which is not too far away.
 

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Today I monitored the coolant temperature using a thermometer probe taped onto the upper hose. Temp rose to 68 C and when the fan cut in it dropped to 54 C. OK, the actual coolant temp was obviously higher but this little experiment showed that the water pump is working. The temp gauge as before moved up rather quickly when the fan cut in. After the fan stopped, the gauge dropped back to 3/4 position. I then did another check and this time I switched on the blower fan and the same thing happened! Then I switched the blower off and switched the head lights on and the same thing happened again! All the while I checked the battery voltage and it was pretty much close to 12 volts. So it was not the drain on battery as I suspected before but switching on other devices are somehow providing an alternative earthing and effectively bypassing the temperature sensor's resistive earthing. But where and how this earthing is occurring is the annoying question I need to find the answer to. Am I in the right track on this?
 

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Ive the same issue 1998 lag 1.9 dti

Usually temp gauge is halfway, but when really stuck in traffice it rises to 3/4 and only goes down when i start moving again. the fan is kicking in.

Maybe its a design flaw?

Also a question, how do you access the Radiator cap, because checking the expansion tank isnt as accurate as opening the rad cap and checking if there is coolant in the rad, as there maybe blockage before the coolant gets to the rad. Can anyone tell me where the radiator cap is located? Usually located on the top of the rad, but that is covered in the laguna by a panel and I cant really see underneath the panel, dont want to remove the panel if there is no cap on the top of it :(
 

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Today I monitored the coolant temperature using a thermometer probe taped onto the upper hose. Temp rose to 68 C and when the fan cut in it dropped to 54 C. OK, the actual coolant temp was obviously higher but this little experiment showed that the water pump is working. The temp gauge as before moved up rather quickly when the fan cut in. After the fan stopped, the gauge dropped back to 3/4 position. I then did another check and this time I switched on the blower fan and the same thing happened! Then I switched the blower off and switched the head lights on and the same thing happened again! All the while I checked the battery voltage and it was pretty much close to 12 volts. So it was not the drain on battery as I suspected before but switching on other devices are somehow providing an alternative earthing and effectively bypassing the temperature sensor's resistive earthing. But where and how this earthing is occurring is the annoying question I need to find the answer to. Am I in the right track on this?
If the engine was running when you checked the battery voltage then it is a little low,the alternator should be charging at around 14 volts,this will drop a little with the headlights on or the blower fan,but not to 12 volts.

I think your on the right track with the earthing problem,I have had the same thing on a 1.8 8 valve Laguna 1 phase 1,check the main earth strap and it's connections between the battery and the gearbox,they have a habit of corroding both internally and at the gearbox end.There are other smaller earths around the engine bay,if the main one isn't at fault then go round and check and clean all the others,you could also check for perfect continuity between the engine and battery/body earths too.
 

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I'd recomend at your next service you get the entire coolant system fully flushed out and ensure the interiro heater matrix is also unclogged as they tend to gunk up.
dotn forget to have the system refilled with antifreeze as renault engines dont like neat water, as it tends to cause furring up of the pipes.
tap water is deffinatly to be avioded at all costs, as algae farms in the pipes are a PITA to flush out...:d
 

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Have you tried bleeding the coolant system. It may contain air. If the temp sensor is sitting in a pocket of air it will not record the true coolant temperature but will once hot coolant suddenly hits it:)

It may also be worth checking the resistance of coolant temp sensors when cold and then when hot:)
 
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