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MG Midget and Sprite Technical - REALLY basic question....
| Hi all, This seems really silly! 1275 Mk 3 Midget Have replaced all of my cooling system ( more or less successfully!) and just about to pop a new thermostat in. Googling this, says to check the new thermostat- but over 45 years worth of driving and playing with cars , I've NEVER done this , and I don't know what I'm looking for to check a' Stat. Could any kind soul tell me what to do and what to look for?- I have the old & new stats if that's any help. I'll get my coat.............. Cheers colin |
| colin frowen |
| Colin,
basically put it in hot water and check when it starts to open and fully open and start to close and fully close if you can. It should start to open at around whatever figure stat you have chosen, if 82c then it'll start to open around 80.5c–84c - and fully open at around 89c–95c. Check your stat has a hole at the side or a bent split pin in a hole. - https://www.stant.com/index.php/english/products/consumer-products/thermostats/abcs-thermostats/ This video shows the basics. - https://www.youtube.com/watch?v=KTwoSgqfuxA Did you decide to fit stat housing and gasket dry? |
| Nigel Atkins |
| Colin, as an example only, photo below of (92C) stat with jiggle pin green circled. BTW - It sounds like that the guy in that video might, as many do, misunderstand the temperature at which the stat starts to open and is fully open. 
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| Nigel Atkins |
| Hi Nigel, Very many thanks- I never even considered looking on Youtube! I'll get my coat............. Cheers colin |
| colin frowen |
| <<if 82c then it'll start to open around 80.5c–84c - and fully open at around 89c–95c.>> Those are quite broad ranges Nigel. Where did you get that data? Is it listed for other nominal stats? Are the start to open figures the same as it cools or do they behave differently when closing compared to when opening? For many years I used to change the stat twice a year, Spring and Autumn so that I ran a higher one in winter. But I don't bother these days. Getting lazy! |
| GuyW |
| As long as it opens and closes who cares? You'll soon see your temperature gauge go into the red if it does not open! As Guy says, there are different stats which have different actuation ranges.
You may also wish to consider a discreet electric fan over the useless and inefficient mechanical thing. It won't alter the operation of the thermostat, but it will direct a tad more engine bhp to your back wheels instead of it spinning a fan unnecessarily. After all, you need as much as you can get at the rear wheels from that wheezy A series..... |
| Oggers |
| Colin,
you do have to be careful when looking on the internet or YouTube as they're not always correct. Usually I'll look at two or three to find the best or most accurate but to give the idea and show how easy it is I think I just used the first vid that was on the general 'All' search. On second quick look at the vid I wasn't too sure it came across as well as it might. I was at that time also looking for a photo of a stat with a V nick hole in but couldn't find one. I was definitely not taking my time with my description of the jiggle pin. It was extremely doubtful that the stat would be faulty but it's always best to fully test a part before fitting, especially as you don't want to be taking that housing off again too soon. |
| Nigel Atkins |
| Guy,
yes very broad range, broadest I could get with the example of a Stant stat that I've given before (other makes available with possibly other figures, I forget what figures though). I usually put something to reference the figures but as I included the link anyone can use it to get the same info I gave here. If I've made a mistake with the figures just let me know. I put the range(s) to more cement the idea that the stat isn't fully open at (exactly), say 82c, as some seem to think. The figures given only refer to opening, nothing was given about closing and I can't remember what if anything I found out about this now so just take the +/-3f as closing discrepancy too, but that's only my interpretation (electric thermoswitch is a different matter). - https://www.gates.com/gb/en/other-products/caps-and-thermostats/thermostats.p.7412-000000-000005.html I looked at all this before but can't remember the details now, some of it I might have put up before (as well as above) if so it'll be in the Archives. I might even have sent it to you in a MS Word.doc(x) er, doc. Other information was that an 82c stat could possibly give similar results to 88c if they were Friday afternoon products but still in production specs (I've not found this when I've twice swapped from 82 to 88 and back again). Stant was the only reference I kept. When I was looking for a photo I tried Gates and noticed at least the one I looked at had MotoRad on it (see photo attached from Gates website). The Stant hyperlink is in my previous post but to save your legs here it is again. - https://www.stant.com/index.php/english/products/consumer-products/thermostats/abcs-thermostats/ 
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| Nigel Atkins |
| Guy,
I've found this for you, I thought you might like it as it contain an "ology" (remember Beattie) but you'd not like the whole thread so just one post. From HonestJohn.co.uk, a 2013 thread called 'Thermostat - How important?', post by Cliff Pope. "This has been a fascinating thread. It has inspired me to go out to the garage and retrieve my box of 'useful' old thermostats and do some tests. 1)All the dud ones (wax type) have stuck in the closed position. 2)The opening temperatures vary considerably from those stamped on the thermostat 3) The extent to which they stay open after the temperature has fallen varies a lot. Some shut the instant the temperature drops below the stated figure, others linger open about 10 degrees. [I'm guessing he means C as that's what others refer to in the thread] 4) The degree of throat or constriction varies too 5) The adjuster screw that some versions have does not alter the opening temperature, only the extent of the gap once it has opened. This will all be basic stuff to anyone doing a degree in thermostatology." |
| Nigel Atkins |
| Nigel, I had followed your link to the Stant page, but didn't see any actual figures for opening and closing there other than the generalisation that they start to open within around 3deg F of the stated figure, and are fully open at around + 15 to 20F. So I was just curious about the more specific figures you were quoting, but only because the ranges were greater than I expected, though I have not really thought about it.
As to performance when cooling (closing)there must be many occasions, especially in winter when the cooling effect at the radiator is greater than heat generation from the engine, when the stat should begin to close down to prevent over cooling. A good stat would be quite sensitive to this and start restricting the flow almost instantly so a quick response both on opening and closing would be important. All a level of finess that I doubt one gets with a knocked down price one from dubious origins. |
| GuyW |
| Guy It's an interesting point ref the cooling effect at the rad being greater than heat generation by the engine, but does the resultant over-cooling matter I wonder? From a thermodyanamic point of view, the more dense the air going into the engine - from coooler air - and the greater the temperature difference when the engine exhausts, then the better and more efficient the engine. |
| Oggers |
| Guy,
I'm surprised at you not extrapolating my figures from the link as I did, either through mental arithmetics, some sort of engineers' slide rule, wall chart or Google as I did. I thought you'd have some ancient and venerable certificate in mathsology. As well as variance in performance from manufacture and new in use how much would there be with age and use over years - and decades. How would we know unless there was monitoring other than watching the temp gauge needle moving, and how much of that is the gauge variance. I notice my most recent temp gauges needles moving more than previous gauges, is that the gauges, the stats or me or a combination of all. |
| Nigel Atkins |
| Oggers, you are of course right that cold air will hold more fuel and give more HP which is why ducting to carbs is often taken from outside the engine compartment. But that doesn't mean the engine should run cooler. Quite the reverse in fact.
In days before cooling systems included a thermostat it was common practice to have a radiator blind - in some cases even adjustable from inside the car with a cord as you went along. The idea became more or less obsolete with the introduction of thermostat valves in the cooling system -- though not entirely so as many cars in the 50's and even later were often fitted with radiator blinds ( or bits of cardboard) as an aftermarket option. |
| GuyW |
| I remember my Grandfather's 1954 Austin A40 Somerset (KJU726) wearing a leather(?) jacket over its radiator grille through the winter. I think it had several panels so you could vary the amount of radiator covered as the weather changed. |
| C Mee |
| I tried one of those rad grille blinds with opening flaps on my 70s MGB one winter time in the 90s, it helped me discover I had the wrong rad pressure cap fitted. Next year I tried painted cardboard, after that I didn't bother. What I should have done is blocked off the totally unnecessary MGB oil cooler, must remember to tell Paul Hunt this, 'e'll luv it. |
| Nigel Atkins |
| Guy
Quite right - cool intake air does not cool the engine! However, leaving the themostat open to the cooling effect of the rad in winter may well cool it more than would otherwise be the case. I was simply suggesting this may actually be beneficial - especially in terms of the temperature differential on the exhaust stroke. Were the radiator blinds more for the benefit of the freezing occupants rather than the engine? - in an effort not to lose precious heat from the engine which could be directed to the cabin, instead of losing it to the cooling system. |
| Oggers |
| I have a radiator blind on my MGA. It is essential on a cold day to enable the engine to get warmer than 50C on the gauge. It operates on a cable to the bulkhead, which transitions using an accelerator bulkhead fitting to a chain inside the car. The ball chain passes through a bracket to allow it to be raised and lowered from the driver's seat. It's a rare option and it took a long time to find one.
I have a 72C thermostat fitted but the engine doesn't get to anywhere near that if the ambient temperature is below 10C. The benefit is reduced wear on the engine. Fitting electric seat heater pads when I recovered the seats did more for passenger comfort. I also had a set of original radiator grill muffs, which had open, closed and half open settings. I never fitted them as I was given the radiator blind a week after buying them! |
| Dominic Clancy |
| Dominic, is the temperature guage sender on your MGA in the radiator top tank then? |
| GuyW |
| If a car is fitted with a thermostat and all the hoses are plumbed up correctly the car(engine) should run at the correct temperature If everything is plumbed up correctly it's impossible for the radiator to overcool the engine |
| William Revit |
I have some radiator blinds for the B, but I've never used them.
|
| Dave O'Neill 2 |
| Dominic, your engine doesn't get near 72C with the blind, or without the blind ? What is the best temperature for this engine ? 72C seems low... Dave, they look nice ! Engineering didn't really evolved since the B: I enclose an extract of my modern user manual. I should have get one now that I live in UK :D 
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| CH Hamon |
| Dave, the one I had was one piece with roll up flaps and straps to hold them up IIRC. I can't remember now if I bought, borrowed or was given it but made for a B as it fitted well and easily. |
| Nigel Atkins |
| Nigel Mine has roll-up flaps and press-studs. Did your B have the one piece grill? |
| Dave O'Neill 2 |
| Dave,
a very rare instance might have happened I might have remembered wrong as I can't remember how the blind accommodated the grille MG badge (I do remember I used a black/red badge instead of red badge on the honeycomb grille as I prefered the look). I'm very vague about the blind I had, you now have me wondering if it was one or two pieces or two pieces clipped together as one. I'm pretty sure it didn't look the same as yours as I don't remember the flaps as being as wide and I think velcro was involved - but it could have been exactly the same as yours for all I know now. You have put me in a mental crisis, shattered my confidence, I need a lie down. |
| Nigel Atkins |
| Sorry Nigel. I hope you'll be able to sleep tonight. |
| Dave O'Neill 2 |
| I am tired of people telling me it can't be true, the empirical evidence is clear and has been constant for YEARS.
When the ambient temperature is below 10C, The 72C is reached with the blind closed almost all the way. With it open all the way a temp of 50C is the max I can achieve. The thermostat is tested, and the engine temp measurements confirmed with an laser thermometer. I am tired of people telling me it can't be true, the empirical evidence is clear. Once the engine is warm I can relax the blind to about half closed and drive all day without overheating if the temperature is below 10C. I have tried with an 82C thermostat, which makes no difference to the observations, except the running temp is higher in the summer. I did try a different gauge, which showed the same result. This is the case with my 1950cc engine as well as the 1622cc predecessors. I have always had new engines hot acid cleaned and balanced, and have never had overheating problems as long as the timing handful mixture are correct. I do have a mesh grille (for looks) fitted. But mot people leave their cars tucked up in the garage when it's colder than 10C! |
| Dominic Clancy |
| Dominic, I am with you - if what you do in terms of engine rebuild and operating the car under different conditions and the car engine does not overheat and gets to the correct temperature then all good, regardless of what others say is 'true'. All part of getting to know old machinery and how to operate it.
Apart from how severe winters were, I wonder how much the introduction/recommendation of multigrade oils made a difference to cars operating in practice in the 1960s? (Rather than monograde oils with a winter 'W' viscocity recommendation as well as a summe version). Ethylene glycol antifreeze at the correct concentration and whether cooling systems were not sludged up must have been a factor too. Radiator muffs seemed to have been a common accessory offered by manufacturers of many models of British cars. Cheers Mike |
| M Wood |
| Dominic I don't question your observations, indeed I have seen similar on previous cars of mine. All I would say is so what? If all the cooling system sees is 50, then providing the correct grade of oil is used, I cannot envisage much of a problem - apart from you freezing in the cabin! |
| Oggers |
| I don't know if I was included in the comment, but I didn't say it was true or not, just thinking that it is pretty cold for an engine. How is the oil pressure ? My 1275 is also pretty cold in the winter, not sharing a lot of heat with me, and the oil pressure higher than during spring/autumn. Didn't people changed grade and oil between summer and winter in the past ? Genuine question |
| CH Hamon |
| Where the temperature gauge sender is installed does make a difference. On early cars it was in the top of the radiator but on later Spridgets it is in the head, presumably to more accurately measure the engine temperature. In the radiator top it measures the coolant, though with the vertical flow rad the sender is in the direct incoming flow from the engine. But only once the thermostat valve has opened. I suspect that air flow around the engine in an MGA is rather better than a Spridget and I can well imagine the engine struggling to warm up during cooler weather conditions, with or without the radiator in the coolant circulation.
No one has really commented in what a good temperature for an efficient running engine is, but I believe the hotter the better but allowing a margin below being so hot that it could sieze. Generally I think around 92 to be a good compromise on a road going engine. I think Dominic's use of his radiator blinds is a good case where without them the engine would be too cool at 72degs for my liking. The only odd thing I thought was if the stat isn't opening, then water isn't circulating through the the rad so it doesn't contribute to cooling, with or without the blinds. However the blinds will seal off a good deal of air flow into the engine bay and be effective that way. Actually, I think this is what rad blinds are supposed to achieve, not simply cutting air flow through the rad, but reducing air flow around the engine bay as well I used to swap stats, using an 82 one in summer and an 88 in winter. The idea was to seal off the rad circulation unless the engine was hotter in winter to compensate for the greater air cooling of the engine, and particularly of the sump oil. |
| GuyW |
| Guy The temp gauge and thermostat only react to the temperature of the coolant not the operating temperature of the engine. Of course it is a good indicator, and quite what the correlation is I know not - depends on a whole host of things I would imagine. I still cannot see any obvious mechanical detriment to running with a lower than normal operating engine temperature. Running too hot though is another thing altogether! Personally I would rather run a tad cooler than a tad hotter. |
| Oggers |
| <<The temp gauge and thermostat only react to the temperature of the coolant not the operating temperature of the engine.>>
Absolutely! With the sensor in the head as on a 1500 midget a characteristic of an engine on the verge of catastrophe is the temperature gauge suddenly dropping! This happens if water level falls in the water jacket sufficiently to leave the sensor probe high and dry at which point the temperature shown actually drops. But you need to be alert and quick to spot it before the imminent HGF or seisure! But yes, engine operating temperature is different, though still linked to the coolant temperature, with the one tracking the other. The other obvious point is that engine temperatures are different all over different engine components, so coolant temperature is usually taken as the nominal guide once an engine has fully warmed and stabilised. |
| GuyW |
| Guy Agreed - I am sure I had exactly that problem with an old Jag. Couldn't work it out for ages until the pressure cap lifted open and spewed all over the engine bay! It would be illuminating to understand whether running "cool" - for want of better words - is indeed detrimental. The only thing I can think of is oil may not permeate as it should, but then if you regularly experience a cooler engine, use a thinner grade oil... |
| Oggers |
| << On early cars it was in the top of the radiator>> I didn't get that, thanks for clarifications! |
| CH Hamon |
| <<extract of my modern user manual>> Cedric, Old manuals used to show you how to adjust the tappets, decoke the engine and reset the timing. Nowadays they tell you how to use a remote key fob button to open the door, and not to drink the anti-freeze. And how to clip and unclip a radiator muffler! All details to stretch the technical abilities of modern Homo (not quite so) sapiens. |
| GuyW |
| A cold running engine is more prone to bore wear. That's what I was always told. Also I was told maximum power is generated at a lower running temperature. Rob |
| MG Moneypit |
| Firstly, who's upsetting people while I'm not here, stealing my job! |
| Nigel Atkins |
| And on to my usual moaning at Cedric - and hopefully passing on some info.
Your 1275 should pass on a lot of heat, subject to the cooling/heating system being clean and in good order. Oil pressure will be about your engine and possibly the cheap syrupy engine oil you use in your engine that doesn't get warm enough on the short journeys. The 20w-50 oil you use in your engine is one oil in one can with additives that make the oil acts as both a 20W (take 'W' as measured at lower temperature) and a 50 (measured at higher temperature). In the old days these would be two different oils in two different cans so each less suitable for use during the opposite temperatures they were designed to be used at. The 50 would be too thick for cranking in the cold weather and the 20W too thin when not colder. I have not explained it well so please say if you need more info or more questions. Sorry but Dave stole my night's sleep. |
| Nigel Atkins |
| Agree with you Guy. Even for some lamps replacement, they simply say "contact your dealership". You need to look for the workshop manual nowdays, which is not (illogically) the equivalent of the Spridget workshop manual, but more the equivalent of the Spridget "Great Book".
Talking about which, Nigel, my cooling system is fine :) Or, at least as much as I can recongnise/check it. I think the problem is more towards the country I have choosen to emigrate to: great cars, amazing people, sometimes sunny but not often warm :p Jokes aside, I found out only recently, that the difference of heat in the cabin between "being on the move" and "idling" is substantial in my car. Makes sense as the water throughtput is linked to the engine speed, but I never quiet realised how big the effect when stuck in London's traffic in winter times :p |
| CH Hamon |
| Cedric,
the blower fan is there to boost air movement when you're going below 25mph. I know what you mean about the water pump but that should make things warmer in the cabin. I thought I'd given you my notes on simple servicing and other stuff and cleaning the cooling/heating system and how to use the heaterbox fresh air flap for heating. But if not just email me. The engine does have to be fully warmed up to get the most heat out of your heater. I've yet to turn the (cylinder head) heater tap on, my wife doesn't want it on because her feet get too hot, I turn it on when it gets colder to clear the screen and warm my feet if we have the top down. |
| Nigel Atkins |
| Nigel Can't your wife close the flap on her side, so her feet don't get too hot? |
| Dave O'Neill 2 |
| Dave that is with the flap closed!
The metal parcel shelf probably also holds the heat into a closer area. Also the exhaust pipe is that side. :) She'd sooner put a blanket over her legs than have the heater on, you'd think we were travelling in a car from 1873 rather than 1973 (although the technology is about the same, except for the ignition timing). :) If both footwell flaps are closed and the roof is up then it often gets too hot for my head. When I'm by myself with the roof up I might open the passenger footwell flap, or roof down open driver's footwell flap, I don't like to be cold but I can't take being too hot. Because I got a sh*t roof and sh*t fitting from Don Trimming it's too much of a risk and pain to take the hood down now the weather is cooler, it was a fight on cooler nights in the summer. But you know me I don't complain about these things I just get on with it. |
| Nigel Atkins |
This thread was discussed between 12/12/2020 and 18/12/2020
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