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MG MGF Technical Oil temp gauge on MY2000 1.8i BBS discussion at MG-Cars.info
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MG MGF Technical - Oil temp gauge on MY2000 1.8i
| Hi, I've put up with a dodgy oil temp gauge since I bought my F in April 2000. After 20 mins of motorway driving it went up to 140c - 150c regularly, and usually hovered around 135c for normal driving. The Rover dealer was no use in resolving this problem whilst the car was in warranty. After doing a bit of hunting through the archives, I found Dieter's MY2000 oil temperature fix and soldered a resistor into one of the cables which appears to have done the job (thanks Dieter!). My oil temperature for normal driving is now 60c and the same 20 minute motorway run just goes up to 65c. It seems rather low. Does anybody else get this sort of reading, or am I just getting paranoid? Thanks, Jason W681 JCB |
| Jason Ratcliffe |
| Mine is usually about 100ish and goes to 120 after a bit of a dibble at high speed on the motorway - never seen it higher but others have especially track days and the like. Try a search as this has been discussed in the past. HTH. |
| Tony |
| Hi Tony, Thans for the reply. I did a search on the bbs archive beforehand and there appears to be a range of results with mine at the lowest end. I'm curious to see if anybody else did this mod, and if my engine really is running at 60-70c. If not, would a different resistor be more appropriate? Jason |
| Jason Ratcliffe |
| Mine sits usually at the 100 mark. I would assume the current to the old temp gauge is dependant on the resistor, what value of resistor did you add ? You can buy temperature stickers from maplins. These permantly change colour with the temparature. They come in various ranges and I would suggest you stick these on to measure the actual max temperature to ensure that the temp wasn't really 140. They are usually used for measuring the temperatures of heatsinks or components or the inside of a case, but don't see why you couldn't stick on the sump or somewhere to measure the temp. I'm assuming the sump and oil in the sump would be the same temperature, so if you got a clean surface it should work, and you can drive the car around then at some time when you get home stop and then look at the max temp it got to. Brian |
| Brian |
| Brian, The resistor is 15 ohm, 0.5 watt , and the link to Dieters page for this mod is http://www.mgf-net.de/oil/temp_failure.htm It's starting to sound like my oil temperature is a little too low to be accurate, and your suggestion is an excellent idea. I'll pop into Maplins on the way home and see if they've got any in. I'm not an electronics wiz, but it's starting to soud like a resistor half as effective may be more appropriate. Jason |
| Jason Ratcliffe |
| >0.5 watt Don't bother with the watt'age. The load is much less. But the bigger mechanical size the resistor is, the easier is it to handle with it. |
| Dieter |
| I doubt that your oil temperature is as low as 60deg C once the engine has warmed up. The ‘working’ temp needs to be between 40deg C and 100deg C. However, to avoid low-temperature sludge, that can form in the crankcase I personally like to see my oil at 105-110 deg C during normal running and would not be concerned at anything below 150deg C on a track day. The viscosity is fine at this temperature. The ‘flash-point’ is well above 200deg C. http://www.mobil.com/UK-English/Lubes/PDS/EUXXENPVLMOSuperS.asp |
| MG Ant |
| Thanks for your feedback folks. It sounds like the gauge is well off the mark. Half an hours motorway driving only pushed it to 70c yesterday, so there's no way it's accurate. I'm going to pop in to Maplins on the way home today and pick up a 7ohm resistor and one of those temperature stickers. Jason |
| Jason Ratcliffe |
| Jason, it might be worth measuring the resistance across the sensor with the engine hot and cold. Then remove the sensor, measure the resistance at room temperature, and then in boiling water. This at least will give you some idea of 'how far out' your gauge and sensor combination is. You can then go on to make your own calibration curve - and compare it with the figures shown on Dieter's webpage: http://www.mgfcar.de/sensor/index.htm As you'll see, the curve is not linear - but and inverse exponential. I guess it all depends on how accurate you want it to be! |
| Rob Bell |
| Sorry, meant to say logarithmic. The figures from the workshop manual gives this equation: temperature = 257 - 71.7 * log(resistance) Where temperature is in Celcius, and resistance is Ohms. HTH |
| Rob Bell |
| It looks like the less ohms (ie less resistance) the higher the temperature. So as yours was reading high you changed it by adding a 15 ohm resistor. So the 15 ohm is too high resulting in the reading of 60, so you could get out your calculator and old log tables ( knew those school tables would be useful, now why did I throw it out !) and work our what it shuld be, or while at maplins try a 10, and 12 ohm or nearest equivalent, but I'd up the wattage, as lower resistor the more current and the higher the heat could be so go for 1 watt for the 10 or 12. See what it reads with the 12 and if 100 then great if too low then try the 10. I'm afraid you have pushed my redumentary o level physics to the limit, but should work, although temp stickers from maplins will give actual highest temp. |
| Brian |
| The problem with the temperature strip is that it will only tell you about the temperature of the casting that you attach it to - and not necessarily the temperature that your temperature sensor 'sees'. In fact, I would expect that a temperature recording on the base of the sump to be quite a lot cooler, thanks to air flow. If they're cheap, then it is worth a go to get a ball-park idea of what is going on, otherwise, I think that rumaging around with a multimeter is the way forward. |
| Rob Bell |
| Hi folks, Missed this thread while I was away and I think my guage has always read high for the 2 years I've had Velma - constant motorway driving will easily get towards the red line mark... With reference to Dieter's page... I this caused by the "guage" (in the dash) being dodgy or the "sensor" (in the engine bay)? I got a new temp guage off ebay recently from a TF and the connections are all different from my 99 VVC one so I couldn't test that... need to rebay that one but was going to get another from an F but if its not the guage then there's no point... Let me know.. Cheers Chris and Velma |
| Chris Tromans |
| Hi Chris, I've bought an 8, 10, and 12 ohm resistor, and am going to try the 8ohm one first. I was initially suspicious about the gauge itself - tapping it makes it go from 150 - 135, but I'm sure the Rover aler would've picked it up if that was the case. I'll report back once I've got it fitted... Jason |
| Jason Ratcliffe |
| It must be an mpi thing my VVC seems to be spot on whilst my mpi model displays all the above symptoms. I might have to take to an auto elec as I am u/s at electrical problems. |
| Andrew Regens |
| Same here - I'm getting my dad to do the soldering bit! I wouldn't want my rather poor soldering efforts to fall apart on me while driving :) Jason |
| Jason Ratcliffe |
| Jason, Cheers.. yeah do report back... and yep, the "tapping it" trick also sends mine all over the place jumping from 150 down to 135 again... Another question.. if it goes into the red on the oil guage do I get a red light on somewhere? By the way - my VIN is bang in the middle of the range listed on Dieter's page and I confirm it is a VVC not an MPi. Cheers Chris. |
| Chris Tromans |
| VVCs but not MPis have an oil temperature warning light mounted between the speedo and rev counter Chris. I can't recall the temperature that triggers it though? |
| Rob Bell |
| I've (or rather my dad has) put the 8ohm resistor in today, and it seems I'm back to where I was before we had one fitted with a normal oil temp of 135c. I'll try plotting the formula Rob supplied and see if a 12ohm restistor will work instead.... Jason |
| Jason Ratcliffe |
| After speaking to my dad again, he's suggesting putting in a variable resistor so we can work it out correctly. I've plotted the the above formula in Excel in 10 ohm increments. The less resistance, the higher the temperature shown on the display. A 10 ohm difference at the upper end could make the difference between 142-151c whereas at the difference for 10 ohm at 100c is +/- 2c. This (probably) explains why tapping the oil gauge when it reaches 150c makes it bounce down to 140c or less. Jason |
| Jason Ratcliffe |
| It will be interesting to see whether the workshop manual figures tally with your experience Jason. There is a note on Dieter's sensor page that suggests that the quoted figures may not be entirely accurate. Variable resistor idea is definitely a good 'un! :o) |
| Rob Bell |
| We've fitted a 10 ohm variable resistor in series to the 8 ohm one. Once I've got it giving a resonable reading, we'll measure the resistance of both and report back. So far, I've got it reading 120c. It's nice to know I can change my oil temp with the twist of a screw! Jason |
| Jason Ratcliffe |
| Hi Jason, Hi Guys Jason - just to say that my 2000 MGF 1.8i has done EXACTLY the same thing. Only started playing up at 2 years old though and since. I think ours were born in the same year and the same month ! How's that for coincidence ?! HGF at 48,000 miles (2 months ago) :-( The numerous MG Dealers have NO idea how to solve the Oil Temperature thing. The latest on Thursday was that it is normal. (Yeah, right.) Oh yeah, and I was told to slow down when this happens. (Sure I will) My Oil Temp Gauge goes up to 150 degrees and into the red (160 degrees +) on a constant cruise of about 4000 rpm motorway journey. Stays at around 120 degrees in urban traffic. I'm not entirely sure what to do. I'm thinking of printing out the instructions for soldering on the resistor and taking it to them tomorrow. I'm only a girl and can do a lot of things, but I'm not sure I could do this myself !!! LOL. BTW - what's an "mpi" ? Any other advice for a damsel in distress guys ? (Fantastic Forum btw) Jo W216 SLE |
| J Bakehouse |
| Ah Jo, glad to see you found this forum. Providing you have a good read through of the instuctions so you know what you're doing you may as well do it yourself. No sense in paying a garage to do something you can do yourself. Plus your MG dealerships sound pretty useless anyway! BTW, mpi stands for Multi-Point Injection. With the F's you either have a 1.8i (mpi) or a VVC. Emma |
| Emma Jackman |
| Hi Emma ! Thanks again for sending me here - it's amazing what can be found on the net isn't it ? It's not so good that the Dealers don't have a clue. Problem with doing it myself though ! I'm not sure which resistor to buy. You're a gem and thanks again. Jo :-) |
| J Bakehouse |
| No probs, I'm sure someone will be along shortly to let you know what to do, having never done this myself, I can't really help you out. This is definately the BBS you need to come to if you have a problem with your F. Emma |
| Emma Jackman |
| Hi Jo, That’s quite weird - mine HGF'd at around that mileage as well. I took it to a non Rover mechanic who put an uprated gasket and changed the cam belt at the same time. My VIN is 514307. I've spent the past week tweaking the variable resistor until the oil temperature gauge shows 120c after around 20 minutes of rush hour city driving and 20 minutes of driving on the motorway at around 3500 rpm. What I don’t know is what the actual oil temperature in the car was. From the feedback above I am assuming it should be 120c, and that my car isn’t overheating. It went to, but not over 150c on the way back from the MG weekend at Silverstone (~140 miles). I knew my oil temperature wasn’t actually 150c as all I had to do was tap the gauge for it to fall down to around the halfway mark. After talking to my dad this morning, we’re going to leave the variable resistor in for now. I’ll get a reading off it today so you know which resistor to get. Fitting is very easy and takes no more than half an hour, but I’d suggest getting someone who knows how to use a soldering iron – I chickened out! Jason |
| Jason Ratcliffe |
| Jason, Jo, the best thing to do is to measure the resistance over the sensor - this way you'll know whether your gauge is mis-interpreting the oil temperature sensor output, or wether it is in fact a faithful representation of what the sensor is sending! The it becomes a question of whether there is a problem with the sensor or, in fact, the oil is genuinely that hot. The former is more likely, but it is best to be thorough. The other approach is to simply replace the oil temperature sensor! They're not usually that expensive (10-15 quid) - so could be worth considering. |
| Rob Bell |
| Folks, You're going to love this one... My 'tweaked' resistor setting is 17.3 ohms! Needless to say, I fell through the floor when I found out, as I was expecting around 12 ohms. Luckily I had the original 15 ohm resistor and when my dad measured it, it read 150 ohms despite having 15 ohm markings on it! Dieter's original modification is therefore correct, and we'll take out the variable resistor later on and fit a 15 ohm one. Jo, if you do carry out this mod, check the resistor on a multimeter before fitting it. Now where's that receipt from Maplins - I'm entitled to a 7 pence refund :) Jason |
| Jason Ratcliffe |
| Hello Jason, Rob and everyone ! Thanks for all that. Jason - I'll check what my VIN number is and let you know. Just out of curiosity I suppose. Really, really weird that our cars are doing exactly the same things at the same times. Rob - have printed out your comments and intend to go fully armed to the Dealer tomorrow, and woe be tide if they try and hood wink me this time !!! :-) I'll keep you all informed ! Thanks a million Jo |
| Jo Bakehouse |
| Interesting - thanks for the update Jason. Good luck Jo - hopefully you'll have the problem sorted soon :o) |
| Rob Bell |
| Jo, Are you coming to MGF10 next month ? As you seem to be London based, don't know where of course, we have a number of ladies that you may like to meet, Jaime from Essex Roadsters, Emma from Kent and Susanne (mgfsoo) from Stevenage, if there are others I apologise for leaving you out unintentionally. Adrian |
| Adrian Clifford |
| Hi Adrian Not sure what MGF10 is ! What's it all about then? Jo :-) |
| Jo Bakehouse |
| Jo, You will find it all over these forums, but this is the link to the MGF Register site, follow the links there to the forum, register and join in : http://www.mgfregister.org/ If you follow this link you will find details of the previous birthday events and a host of other things you may like to join in on : http://homepage.ntlworld.com/tim.morris4/SEF.htm Adrian |
| Adrian Clifford |
| Jo, MGF10 is the event of the year! Have a read of the websites above, then post your application form! Emma |
| Emma Jackman |
This thread was discussed between 30/08/2005 and 19/09/2005
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