Car mildly overheating
  • Register
  • Help
Results 1 to 21 of 21
Like Tree5Likes
  • 1 Post By jo proffi
  • 1 Post By alan moore
  • 1 Post By Peter Chisholm
  • 1 Post By neil s
  • 1 Post By JohnW

Thread: Car mildly overheating

  1. #1
    1000+ Posts Beano's Avatar
    Join Date
    Mar 2004
    Location
    Brisbane
    Posts
    2,987

    Default Car mildly overheating

    Apart from a couple of Peugeots, I own a Mitsubishi Magna which is currently giving me grief. And the Magna forum appears to be dead...perhaps the owners have gone away for Xmas ?? So I am posting here in desperation.

    Advertisement


    After 4 years of the temperature gauge staying on half-way, it has decided to go up to 3/4.....a couple of times even more.

    The thing is : it doesn't get hotter only at the lights (which would indicate it is the radiator fan). It also gets hotter as I am driving along.

    However it behaves fine and cools down if I have the air-conditioning on. Which leads me to believe that it IS a fan.

    I have replaced the coolant temperature sensor (which goes to the ECU) with a new one. And I have replaced the thermostat with a known good secondhand one, but the symptoms remain the same.

    Magnas have two fans, which may be multi-speed. At least one of them is 2-speed.

    Can anyone shed some light on this, please ??

  2. #2
    Too many posts! JohnW's Avatar
    Join Date
    Jul 2001
    Location
    Perth, WA, Australia
    Posts
    10,667

    Default

    I've had those symptoms caused, almost certainly, by a dodgy connection at the temperature sender unit. Alarming, but no problem after some time of worrying about it and chasing fan problems. Fiddle the connection and see if the gauge changes perhaps.

    (Not a Magna, by the way.)
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  3. #3
    1000+ Posts jo proffi's Avatar
    Join Date
    May 2003
    Location
    sydney
    Posts
    8,372

    Default

    Quote Originally Posted by Beano View Post
    However it behaves fine and cools down if I have the air-conditioning on.
    Just leave the AC on 100% of the time.
    Jo
    BIGRR likes this.

  4. #4
    1000+ Posts Beano's Avatar
    Join Date
    Mar 2004
    Location
    Brisbane
    Posts
    2,987

    Default

    I do these days. But I like to get to the bottom of problems.

    Also, I forgot to mention that I put in a new radiator only a year ago.

  5. #5
    1000+ Posts alan moore's Avatar
    Join Date
    Oct 2001
    Location
    Ipswich, Queensland.
    Posts
    1,873

    Default

    So your fans work when the A/C is on, so the relays and fans are OK, but what about the temp switch in the radiator, which I think Magnas still had, rather than being switched by the ECU. It may be a dual temp type, and so would have 3 pins.
    JohnW likes this.
    '56 Renault 750 (16TS Power)
    '62 Renault Dauphine Gordini
    '89 Renault Alpine GTA V6 Turbo
    '08 Renault Megane sedan

  6. #6
    1000+ Posts Beano's Avatar
    Join Date
    Mar 2004
    Location
    Brisbane
    Posts
    2,987

    Default

    No....definitely no sensor in the radiator. I didn't see one when I replaced the radiator, and I also just went and had a look in case I had forgotten.

    All I can think of is that it is a fan malfunctioning partially (as they apparently have 2 speeds) or intermittently. I have watched them with the car idling, and I have seen the second one on, but it does not come on often.

    Hmmm...perhaps I should observe it again.

    Temp light still stays on half-way (as it should be) with air-con ON.
    Last edited by Beano; 9th December 2017 at 02:09 PM.

  7. #7
    1000+ Posts Peter Chisholm's Avatar
    Join Date
    Aug 2004
    Location
    SWOTR
    Posts
    3,433

    Default

    Really does sounds like a fan problem. Silly question but is it possible that one of them is spinning the wrong way?
    Wildebeest likes this.

  8. #8
    1000+ Posts robmac's Avatar
    Join Date
    Nov 2004
    Location
    Melbourne / Caulfield
    Posts
    18,432

    Default

    Just quietly, I'd be checking for combustion products in the coolant AKA a small cylinder head leak.

    I saw the same behavior on Ancient Toyota Landcruiser on a outback trip some 40 years ago.

  9. #9
    Fellow Frogger!
    Join Date
    Oct 2010
    Location
    Sydney
    Posts
    346

    Default

    OR..... do the old 504 trick and wire the fan/s to a switch so you have control from inside the car. If the fan/s turn on this way and the temp goes back to normal you have the source of the problem and in any event, you wont overheat.
    JohnW likes this.

  10. #10
    1000+ Posts
    Join Date
    Nov 2005
    Location
    Geraldton
    Posts
    1,531

    Default

    Other than the temp guage reading high are thee any other signs of overheating?

    Done any jigging about under the dashboard that may cause the guage to read not as it should?
    Daily Drivers: R10, R12, R17T(?) Decouvrable

    In the Shed(s):
    R8 (1.4 motor, 4 shock rear end), Dauphine, Pugeot 404

    In the Past:
    Dauphine X2, R10 X lots, R12 X2, R16TS, R17TS

  11. #11
    Too many posts! JohnW's Avatar
    Join Date
    Jul 2001
    Location
    Perth, WA, Australia
    Posts
    10,667

    Default

    Quote Originally Posted by Exfrogger View Post
    Other than the temp guage reading high are thee any other signs of overheating?

    Done any jigging about under the dashboard that may cause the guage to read not as it should?
    Agreed.

    Or, indeed, as I mentioned earlier, have you checked whether wiggling the wire AT THE SENDER UNIT changes the gauge reading......
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  12. #12
    1000+ Posts Beano's Avatar
    Join Date
    Mar 2004
    Location
    Brisbane
    Posts
    2,987

    Default

    Quote Originally Posted by Peter Chisholm View Post
    Really does sounds like a fan problem. Silly question but is it possible that one of them is spinning the wrong way?
    Fair question, but not possible. There are two fans in tandem and they plug in to the wiring harness using plugs which cannot go around the wrong way. Plus, the car behaved itself for at least 6 months after the new radiator. The first symptoms appeared to me to be a lazy thermostat.....then got slightly worse.


    Quote Originally Posted by Exfrogger View Post
    Other than the temp guage reading high are there any other signs of overheating?

    Done any jigging about under the dashboard that may cause the guage to read not as it should?
    No and no.

    Quote Originally Posted by JohnW View Post
    Agreed.

    Or, indeed, as I mentioned earlier, have you checked whether wiggling the wire AT THE SENDER UNIT changes the gauge reading......
    Good point, but I haven't tried this yet.
    There are two units : a small one with one wire going to the temp gauge on the dash, and the other is a sensor (which I replaced with a new one) which goes to the ECU, which apparently tells the fan (s) to cut in at different speeds.
    If there was a loose connection to the sensor going to the gauge, the temp gauge would read lower.

    Haven't tried wiggling the other one. I might try bypassing the plug arrangement completely (at least temporarily) to ensure that connection is not suss. Perhaps sticking some needles through the wires "upstream", attaching some wires, and then directly to the connectors coming out of the sensor ?


    Quote Originally Posted by robmac View Post
    Just quietly, I'd be checking for combustion products in the coolant AKA a small cylinder head leak.

    I saw the same behavior on Ancient Toyota Landcruiser on a outback trip some 40 years ago.
    Urk !
    I hear you, and I may get it checked (esp before Xmas hols), but this model Magna is not known to blow head gaskets at 199,000 Ks, which mine has now done.

    Though I am tending to be in denial about it, because with a timing belt kit + water pump, having head gasket failure on a V6 (argh... two heads !) would mean an economic writeoff. I'd rather invest money in a lower kilometer car than into a 200,000 K Magna. Even if I did all that work myself, it'd be a pain.


    Quote Originally Posted by neil s View Post
    OR..... do the old 504 trick and wire the fan/s to a switch so you have control from inside the car. If the fan/s turn on this way and the temp goes back to normal you have the source of the problem and in any event, you wont overheat.
    The temperature is fine if I have on the air-con ....which means that both fans are on. But it worries me that both fans need to be on....it makes me suspicious that what Robmac says is possible is actually true.

    Either that or the new (secondhand) thermostat I recently put in is producing identical symptoms as the original one, which I suspected of being lazy.

    Perhaps I should hack the guts out of the old one, put it back in, and see how the temp goes ?

    I was disinclined to buy a new thermostat (just "on spec", without knowing definitely that it is stuffed) because they are $90.
    Last edited by Beano; 9th December 2017 at 09:53 PM.

  13. #13
    Too many posts! JohnW's Avatar
    Join Date
    Jul 2001
    Location
    Perth, WA, Australia
    Posts
    10,667

    Default

    Wow, expensive thermostat.

    With my CX, the gauge actually reads higher with a poor connection at the sender unit. This is quite the opposite to my logic, and yours (!) but I double checked.... it reads zero disconnected but higher temperature with a poor (resistive) connection, so I'd still check that option carefully. In my case the gauge is a proper galvanometer, so responds immediately. Not sure whether your Magna has that type or the common slow-to-respond type.

    Hope it isn't a head gasket.... Something has changed, that's for sure.
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  14. #14
    1000+ Posts Peter Chisholm's Avatar
    Join Date
    Aug 2004
    Location
    SWOTR
    Posts
    3,433

    Default

    If you reckon the head gasket is on the way out and it may be the cause of the problem what about putting some "goo" in the cooling system and see if it makes a difference?

  15. #15
    1000+ Posts Beano's Avatar
    Join Date
    Mar 2004
    Location
    Brisbane
    Posts
    2,987

    Default

    My wife has been pestering me (as they do) about taking her to Natural Bridge (also called Natural Arch) in the Gold Coast hinterland. So today I traveled over 300 Km and gave the car a bit of a workout.

    Going down the motorway at 100 Km/h with air-con OFF......no probs. Temp gauge sometimes (surprisingly) even just a tad under half-way. Magnas usually sit right on half.

    Up into the mountains it started to get hotter (as I expected) and I had to turn on the air-con. After that no probs, no matter how I fanged it uphill.

    Back up the highway with no air-con, no probs again. Getting stuck in slight traffic jam on the way back....had to put air-con ON again.

    My conclusion is that one of my fans is not working on one of its speeds. I have in the past observed it working (full on, I think) when the air-con is ON, but the fan soon goes off after I turn off the air-con.

    I shall fit a new fan this week and return here with the result. I'm pretty sure its the air-con fan which is only working on HIGH.....when I have the air-con ON.

    I would have expected the "normal" fan (which goes pretty fast almost every time I have observed it) to have been enough to cool the radiator.....it sucks air through half the damn thing.

    Thanks to all for your input in my little drama so far. I shall return !

  16. #16
    1000+ Posts Peter Chisholm's Avatar
    Join Date
    Aug 2004
    Location
    SWOTR
    Posts
    3,433

    Default

    You know this reminded me of the time back in the year dot that my father, sister and I, for some strange reason, decided to drive up through western NSW on to White Cliffs. Interstingly, we chose to embark on this voyage during a hot summer, travelling in the unmaintained 404 station wagon. The dodginess of the cooling system became very apparent when we had to regularly turn on the heating full pelt to try and cool down the engine. Winding down the windows did not nullify the effect of the heater. It was one very long and hot trip.

  17. #17
    Fellow Frogger!
    Join Date
    Mar 2013
    Location
    olinda victoria australia
    Posts
    671

    Default

    Not a silly question - I had just this happen on the DS after a service. My fan was organised so I switched it on manually once I was beginning to be unhappy with temp. Took a little while to puzzle it out, but the giveaway for me was when it all got worse after the fan was switched on ( air squirting through front of radiator gave me a broad hint too ). Mechanic had put leads on wrong way round. Easy to do

    May not leap out in quite the same way if fan is being thermostatically switched

    Good thought

    ANdrew

  18. #18
    Too many posts! JohnW's Avatar
    Join Date
    Jul 2001
    Location
    Perth, WA, Australia
    Posts
    10,667

    Default

    Quote Originally Posted by Andrew Watkins View Post
    Not a silly question - I had just this happen on the DS after a service. My fan was organised so I switched it on manually once I was beginning to be unhappy with temp. Took a little while to puzzle it out, but the giveaway for me was when it all got worse after the fan was switched on ( air squirting through front of radiator gave me a broad hint too ). Mechanic had put leads on wrong way round. Easy to do May not leap out in quite the same way if fan is being thermostatically switched Good thought ANdrew
    And I've just found the CX doesn't seem to be switching automatically to high speed from low speed fans! Manual switch seems a really good idea right now!!
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  19. #19
    1000+ Posts Beano's Avatar
    Join Date
    Mar 2004
    Location
    Brisbane
    Posts
    2,987

    Default

    There is something decidedly weird going on here.

    Just ignore the air-con fan for a minute. If I get the car running at operating temperature, open the bonnet, and put my hand down behind the "regular" fan, on the inside end next to the shroud, there is hot air rushing out. But when I put my hand on the other side....the outside half of the shroud....the air coming through is NOT hot !
    I have done this separately ...twice..... because I coulodn't believe my senses at first.

    If my radiator was not new less than a year ago (bought it from AutoBarn) I would suspect a blocked radiator at one end. Simple.
    But it WAS new.....less than a year ago. However all I can think of is that it IS blocked, up one end.....somehow....although I keep it really clean and full of coolant (which is admittedly due for a change).

    So the coolant is going mostly down one end....the end which has the air-con fan mounted over it.

    Here is the setup : water enters it via the top hose (on the drivers side), going across the top tank (it is not a crossflow) and down all vanes, exiting the bottom tank, passenger side, and into the bottom hose.

    The top hose is hot. The bottom hose is also hot, but slightly less. It's hotter than i would expect but I'm no expert.

    I wonder if the water pump impellor is worn out ? Mitsubishi told me they are not known for doing this and although the car has just under 200,000 Ks, the cooling system is in great condition....there is no crap in there. I have owned it for the last 80,000 Ks.



    The next thing I need to do is drain a little fluid and look down the radiator filler neck with engine at operating temp, to observe if coolant is rushing past. Though I doubt if a lot will be.

    There is no baffle in this type of radiator, and I cannot think of anything which might clog it up. But half of it MUST be clogged.
    Last edited by Beano; 11th December 2017 at 09:05 PM.

  20. #20
    1000+ Posts Peter Chisholm's Avatar
    Join Date
    Aug 2004
    Location
    SWOTR
    Posts
    3,433

    Default

    Curiouser and curiouser. It does sound like a coolant flow issue.

  21. #21
    Too many posts! JohnW's Avatar
    Join Date
    Jul 2001
    Location
    Perth, WA, Australia
    Posts
    10,667

    Default

    Hmm. I'd go and buy one of those temperature sensing IR guns from Toolmart, Supercheap or wherever. They aren't too expensive. They have an on/off laser pointer too, so you point them and press the button and can see exactly where it is sensing the temperature.

    This way you can measure temperatures in various places, reliably, and work out in degrees what is going on. I have, for example, 95-105 coming out of the head in the top hose to the radiator, but 82-85 in the bottom hose through the transmission heat exchanger at the radiator outlet. Cylinder head temperatures around 95.

    The tools are really good, and stop speculation as you have numbers!! You can measure the top and bottom hose temperature and even scan across the radiator core and get a sense of the temperature distribution.

    I'm fairly sure after the last couple of days that my high temperature coolant switch isn't turning on the high speed fan mode.
    COL likes this.
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •