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MG Midget and Sprite Technical - Coolant temps

Hey everybody. I'm still working out bugs in my '72 1275 and need to throw a question out to the gurus. I went on the first cruise of about 40 miles today to check out the running coolant temps. In stop and go driving , she's running about 190, when I get over 50mph on the highway she moves up to around 200. As I come off the highway it comes back down. Too high? I haven't really done anything but flush the original radiator. Thanks CJ
C. J. Charvet

200 degrees is getting near the danger zone. Have you removed the thermostat? If so, you need to put in a restrictor to slow the coolant flow. If there is no thermostat the coolant moves too quickly thru the radiator & it can't remove the heat efficiently. I always ran a 185 stat & never had a temp problem even on the hottest summer days.
Mike G

I replaced the t-stat when I rebuilt the motor. It's a 160 degree I believe. I have read on the archives that some have used the blanking plate with the t-stat. Anyone have any experience with this? Thanks Mike.
C. J. Charvet

C.J. The thermostat controls the minimum operating temperature, not the maximum operating temperature. Your 160 deg F thermostat should be fully open, allowing full water flow, at 180 degrees F. Mike's 185 degree thermostat would allow full water flow at 205 deg F.

First, 200 deg F is not excessively hot. Modern cars are designed to run at such temperatures and higher. One of the reasons that they last longer--the higher operating temperature actually results in reduced engine wear. Something we have learned since our cars were first designed.

Second, what you are worried about is the engine getting so hot that the cooling system boils over. Your radiator pressure cap allows the system to pressurize. Each one psi increase in the pressure within the system raises the boiling point of pure water by three degrees F. Thus, a seven pound pressure cap raises the boiling point of pure water (212 deg F, at sea level with "standard pressure) to 232 degrees F.

Add in "anti-freeze" which is less efficient at cooling than pure water, but is more efficient at flowing through the engine and has a significantly higher boiling point. Very unlikely that you will have a problem with boiling over.

Third, add in the fact that both the cylinder head temperature sending unit and the temperature gauge are over 28 years old. I have used an IR thermometer on cylinder heads which the dash gauge demonstrated were running "above normal". The average temperature rating of such cars was in the mid 180 degree F area.

If the radiator boils over, or if the engine begins to run poorly, you may have a problem. If neither of these happen, ignore the "problem" and enjoy the drive.

Les
Les Bengtson

Thanks for the info Les. Not close to boiling over and the she runs great so I'm just keeping an eye on it as I haven't had her out on many long runs. Great pressure in the cooling system too. Do you think using a blanking plate would keep temps lower at highway speeds? Most of the overheating problems I've ever had were in traffic. Mine runs hotter at speed. Maybe I've just got this car about done and I can't find anything better to fiddle with. Not a bad problem to have.
C. J. Charvet

Hey CJ

I know what your saying, and even though les makes good scence...its a whole nother thing when your watching the temp in going up up and up...lol

I cant tell you anything on the blanking plate, sorry

but did you mix the fuild 50/50...also look to see if the heater valve is open


a good cheap fix thats good for 10 degrees is "water wetter" or mabe its "wetter water" auto stores carry it ...and works really good.

how hot was it in FL. when you where driving around...I know driving down the road when its 90 degress or higher the engine heat really takes off

also take alook at the back of your rad. alot of times its hard to get the engine and rad back into place with out scrapping the finns of the rad on the fan blades...they make a comb to straighen those fins out....I use cardboard taped to the back of the rad to protect the finns from getting smashed...also look to see if there is a big build up of paint on the front of the rad....you might want to try a boil out of both the rad and heater core

prop
Prop

Thanks Prop. It's usuallly around 90 degrees here. it might have been a little cooler yesterday but no difference in coolant temp from hotter highway driving. Thanks for the extra tips.
C. J. Charvet

I'll ask the obvious... is your belt properly tensioned? And what is your idle speed? A slight increase in idle speed can some times help the over heating in traffic problem.
Trevor-Jessie

Sometimes we need to be reminded of the obvious right? The tension is good, and my idle is right at 1000 rpm. Temperature actually goes down when driving slow or in traffic. The temp holds right at 195 today at 50-55mph, or about 3000 rpms. It is HOT today!
C. J. Charvet

C.J to beg a small thread hijack, if it is HOT today in Florida have you or anyone else heard yet from John and Pom Collins who are taking the trip down to Fla from New York about now?

It'd be good to hear how they are getting on...

Sorry for the hijack
Bill

I had some serious overheating first then recored the rad and fitted a 160 thermostat and drilled 2 3 mm holes in the flange.

Now it stays solid at 160 and only when its very hot outside and I am doing a lot of city driving it moves a little towards 190. Never went above since then.

The 2 holes let some of the coolant pass the thermostat. 2 reasons: first the thermostat reacts quicker and if it is locked in closed position there is always some flow. A wise mechanic told me that trick. Its better then a blanking sleeve. That one will cause wear everytime at startup. I wont use that unless you live in the sahara.
Bas Timmermans

Hijacks are welcome, Bill. Haven't heard anything on anyone traveling to Florida but all are welcome. U.S. 1 and I95 (If your crazy)pass through little old Titusville. Drop me an email if anyone wants to meet up and talk midget over a beer.

Bas, thanks for the input. My t-stat opens pretty quick so I'm not sure drilling it would really matter.
C. J. Charvet

cjcharvet@gmail.com

C. J. Charvet

Hey CJ

When was the last time you changed out the rad cap, maybe its time....cause they are all made in china I change mine on all my stuff once a year when I flush and put in new stats


prop
Prop

Just changed it. It's got great pressure. thanks.
C. J. Charvet

did you try this....you can get it at most auto parts stores,,,I use it and swear by it...its good for an extra 10 degrees...but to much has the oppiste effect just like anti fresse is to strong


prop

http://cgi.ebay.com/ebaymotors/TRIUMPH-SPITFIRE-1979-OVERDRIVE-TRANSMISSION-TESTED_W0QQitemZ220264664946QQcmdZViewItem?hash=item220264664946&_trkparms=39%3A1%7C65%3A10&_trksid=p4506.c0.m245.l1318
Prop

Yeah that will cool it down...a 5 speed works everytime....LOL



try agian....

http://www.redlineoil.com/products_coolant.asp
Prop

Nice transmission! Think that will mate to a 1275? I think I'm going to check out the water wetter. Thanks Prop
C. J. Charvet

It wont fit your trans tunnel:-(
Bas Timmermans

Centigrade temps would be???
Daniel Thirteen-Twelve

not sure what the temp is that you want to convert....


but here is a great little conversion chart.....

http://www.embassyworld.com/data/Temperature_Conversion.html


prop
Prop

This thread was discussed between 03/08/2008 and 04/08/2008

MG Midget and Sprite Technical index

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