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MG Midget and Sprite Technical - 1275 running cool

Hello all, and thanks for the view. I have a '74 midget with the original 1275. The coolant bypass hose is still in place, the thermostat is a standard 180 degrees. The fan is standard: no electric add-on. No oil cooler. The radiator is new, temp guage and stat are verified working correctly. Now that's out of the way... Funny thing is that unless it's screeming hot outside, the engine is running well below 180... about half way to the temp guage N. After trying to work through this on my own, I've read a few bits that say to be sure your stat has a shield that blocks-off the bypass channel as it opens. This makes sense to me, but no one seems to sell such an animal. I'm a nut about running it stock, and really want to find the right solution rather than to blank-off the bypass or fudge the stat to a higher temp version. If it would run at 180, I'd be a happy guy. Many thanks
SS Schwartz

Hi SS,

unless very warm outside the 1275 with X-flow rad shows well below 'N' (or 180) whilst going along but when you hit traffic or switch off it will go to 'N' or above

180 (82 over here) stat are standard

don't do anything just go out and enjoy your car be happy it keeps cool

allow for variances in gauges but note where yours show when the car is running well and in good condition and that's what's right on your guages in your car

unless there is significant deviation don't worry too much
Nigel Atkins

Thank you very much Nigel... sound advice.
I can't help but be baffled at a stat that openes at 180 (verified), and a gauge that reads spot-on "N" at 180, yet it motors down the road well below 180.
PS - "Well below" I understand is relative, since the temp difference from half-N to N is (I'm guessing) only about 20 degrees F.
SS Schwartz

I think, as a totally non-mechanic, that the radiator over performs and the belt driven fan under performs

if your system wasn't working so well I'd say do as I've done thoroughly clean your cooling system and swap to a thermoswitch controlled electric fan and get rid of the engine driven fan and don't worry about overide switches - but save your money (for at least 12 months of regular driving as you may need it for other stuff on the car)

I take my temp readings from which letter the needle covers of 'WATER' from my driving position, mine's usually around the 'T'

here's a photo I lifted from somewhere so slightly blurred (note letters are in a different place)

Nigel Atkins

Interesting... If yours is a 1275 gauge (the right one on your image), 'needle over the T' is exactly where I'm reading. Thanks again!
SS Schwartz

in the winter it was sometimes at the start of 'A' because I kept forgetting to make a radiator blind

Sheldon, if you want to you can click on 'Customise' and alter your title to include your first name and if you want to click on my 'View vehicle profile', scroll to bottom of that page and follow intstruction to add your car's details and photo
Nigel Atkins

Maybe it's just a "cool" 1275. Most kids these days think Spridgets are pretty cool too. :)
Lawrence Slater

IIRC there are two thermostats you can use: an 82 and an 88 I think. I believe and I may be wrong, that they open at 82 and 88 degrees.
I swapped the original for a hotter one and that has made the engine run a little warmer.
Mine runs a thermostatic electric cooling fan (Revotec)(with no mechanical fan) but after it failed to cut in last summer I fitted an over-ride switch - it saves me worrying about will it or won't it cut in as the engine temp starts to rise on the wrong side of N.

Jeremy 3

Certainly in cooler climates an 88 degree thermostat is advisable.
Otherwise the oil will never get anywhere near ideal temp (low water temp means low oil temp)

Mine runs just before the 190 mark and on a hot day in trafic at the 190 mark.
If it goes to the mark between 190 and 212 it starts to run rough (only happened after a failed heater tap)

In winter I block of the oil cooler and about half the radiator to keep the temp up.
Onno K

Jeremy,if my Revotec thermoswitch done that I'd be straight on to Revotec, if you got a thermoswitch that doesn't switch off it's not doing it's job

in a modern car you don't have to rely on an overide switch so you should have to with a modern electric thermoswitch and fan made by Revotec

as Onno said the 88 thermostat is supposed to be for colder climates, I think when you're running at 190-212 a bpart of the problem will be the petrol/carbs getting hot

I now feel uneasy if I see mine at just after the 'N' (190) or even on the'N' if I'm going along
Nigel Atkins

Nigel said " Allow for variance in gauges". Allow for variance in the ancillaries as well.

Although you don't say you've changed yours, FWIW I have run two different temp senders in my car, with no other changes, and the difference between them is more than one hour on the clock, how many degrees that is I can't say as it's the stock 1979 1500 gauge, but I'd guess more than 20 degrees anyway.

Richard Reeves

very good point Richard with the electric temp gauges

Simon having a 1275 will (probably) have the pipe and bulb type (forget what it's called) rather than the later electric

if I sound condescending I don't mean to be just putting a quick post
Nigel Atkins

Your spot on Nigel. It's not the newer electric type, but a direct reading bulb (that reads exactly "N" at 180). Also, thanks for the profile suggestion... I'll get on that!
SS Schwartz

putting up your car's profile can sometimes help with the confusion of models (a bit)

however some wont check even though it's there, as is their right of course
Nigel Atkins

you're right the oil temp was the main reason for changing the thermostat to a hotter one and Congratulations on your recent wedding using wedding cars sevenoaks (you have just got married haven't you?)

Nigel the fan was bought from ebay and is well out of warranty, otherwise I would like you, be in touch with Revotec. The fault is intermittent - so the additional manual switch is my contingency, I do like my contingencies!
Jeremy 3

intermitent might mean wires or connections are not fully clean, secure and protected

did you get the Revotec thermoswitch and relay and Revotec fan

to test yours try wiring directly to battery (with an in-line fuse for contingency), get the engine warm and you can then test the thermoswitch by turning it up and down through the range

I used seperate earth points for fan wiring and switch/relay to be sure (contingency)

and mine is straight off the battery with an in-line fuse so that it runs on after I've switched the ignition off and left the car

I took it off the ignition as I wasn't sure if it was cusing the car to run-on and never put it back prefering it the way it is

if I was doing it again I'd get a deeper fan to hopefully cool quickerand bring the temp down more in traffic as there's too much difference in temp when travelling and in town traffic
Nigel Atkins

This thread was discussed between 23/05/2012 and 25/05/2012

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