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MG MGB Technical - Which thermostat

Hi,

I am rebuilding a 1975 MGB engine for a friend.

The Haynes manual says that a 160 degree thermostat should be used in the summer. Can anyone speak this?

Heavens sake, I can't remember putting a 160 degree thermostat in a car since some time in the early 1960's. I am in Southern Alberta, Canada. Yes I am an old Fart, now!

Thanks---Layne Wilson
Layne Wilson

Layne, read the thread I started "Overheating Water Pump Problem"...

There is a link to a sight about thermostats, plus other usefull information. You may find this very helpfull.

Don 1979 MGB
Don

Hi Don, Penna

The "Overheating Water Pump Problem" article was interesting, and the article about the sleeve used to block the coolant that bypasses the radiator.

Yet, I still do not know if I should use a 160 degree or a 180 degree thermostat.

Layne Wilson
Layne Wilson

I recommend a 195ºF thermostat -- that's what I use year-round. You want to run the engine as hot as is practicable for the best longevity, efficiency, and power.

Older engines were often fitted, I believe, with cooler thermostats in an effort to keep the oils of the day from breaking down due to the heat. Modern oils are MUCH more heat tolerant and need no such coddling. ;-)

HTH!
Rob Edwards

Rob
I echo your points. I run 10-40 oil with a 195f thermostat and don't lose fluid and maintain hi oil pressure. The higher temps will get the moisture/condensation out of the oil quicker and lengthen lube and engine life.
Barry
Barry Parkinson

Layne. For your use, use either the 180 deg F, or the 195 deg F thermostat. All of the studies I have read demonstrate that Rob is correct and engine wear goes down when the engines are run at 200+ deg F. Most modern engines run significantly hotter than the older engines did and this is a designed in feature. Rob is also correct that modern oils are designed to cope with this additional heat and provide much better protection than the oils did 35+ years ago. A 180 deg thermostat will be fully open at 200 deg. A 195 deg thermostat will be fully open at 215 deg. Either is an acceptable operating temperature if the cooling system is in good condition.

I have a tech article on the cooling system on my website, www.custompistols.com/ under the MG section. I have, several times, had people come to me because "their MGs are running hot" as indicated by the dash gauge. When I put my IR thermometer on the cylinder head, the reading is normally under 190 deg F. Old dash gauges and cylinder head temperature sending units are often the main cause of "running too hot". My tech article tells how to use a meat thermometer, inserted into the radiator, to cross check the gauge against the actual running temperatures.

Les
Les Bengtson

The old way, as I remember it, was to run a 180 in the summer, 195 in the winter. The first 2 years I had my latest car, that I drive year-round, I changed to the 195 in winter. Too lazy the last 2 years, I left the 180 in and haven't noticed any difference in the heater, the 195 never reached anywhere near the 195 mark anyway when it's cold out (sleeved 'stats).

Hopefully it runs a bit cooler in the summer with the 180.
Tom

Empirical experience over 18 yrs:

I use a combination of the blanking sleeve AND Robertshaw's (now sold as a Prestone Power Performance unit, # 330-195) "balanced" thermostat design. It is a slightly different looking T-stat and by its design it simply ensures that the t-stat opens only for temp changes, and is not forced open or closed by pump pressure or suction. Here is a link to a discussion of these T-stats: http://www.flowkooler.com/thermoover.html.

Why the blanking sleeve? I quote from an old webpage put up by Neil Cotty, Australia, about the OEM t-stats used in the MGA (which pretty much applies to all B-series BMC/BLMC engines):


"As you can see it is very different to the replacement part we are familiar with today. The original thermostat has a moveable sleeve. When the thermostat opens it allows fluid to pass into the radiator as a std thermostat does, but the sleeve itself slides up and blocks off the bypass port in the cylinder head.

"This bypass port runs through the cylinder head and directly to the water pump. It is present on all MGA & MGB castings. When the port is open, the engine is able to recirculate a small amount of fluid from the cylinder head itself to the water jacket of the block. This enables the engine to warm up a little faster. When the system is up to thermostat opening temperature, the sleeve moves up and blocks off the port, ensuring full flow is directed into the radiator for maximum cooling efficiency.
One of the reasons why a blanking sleeve is necessary when racing is because of the bypass port, ie not ALL water is passed through the radiator so the system is not working at 100% efficiency. With the std replacement thermostat, our MGA's and MGB's, Magnettes etc are not operating at peak cooling efficiency when the thermostat is open.

"If you are an original B owner, and you are wondering why your car didn't come with one of these, it's because these thermostats stopped being made prior to the MGB, during MGA production. It seems they were unreliable. ;-) <G> It still begs the question why the port was kept in the cylinder head, when the replacement was obviously not able to provide the intended functionality!

"On advice from my Supplier, I fitted a std replacement thermostat & thermostat blanking sleeve. A 1/8" hole is also drilled on the thermostat horizontal flange to avoid pressure build up in the head when the thermostat is closed. The effectiveness of the seal with the blanking plate or original thermostat has to be questioned, as it does not look like it would close the port off entirely. That said, fitting the blanking sleeve effectively blocks the port off as much as it is possible without resorting to more extreme measures.

"Implementing the above in itself is fine in a Country like Australia where our concerns are with Heat, not cold, but what side affects are there to this modification? Well first the good news. I have noted a 10% reduction in temperature when I performed the preceding modification. Result? The car no longer overheats, it still gets warm on the temp gauge but the car is not adversly affected by the increase. The car also appears to warm up at a normal rate."
FYI/FWIW
Bob Muenchausen

http://www.carnut.com/ramblin/_cool3.html

Fast warm up and flow tends to be a driver to the current use of 0Wxx oils or 5W20 in modern engines.
Paul Wiley

Hi,

Thank you all for the information.

You have confirmed my view that I should change the 160 degree F thermostat that was in the car to a 180 degree, or higherone.

The car is a lady friends of mine. A friend of hers had overheated the engine, and I agreed to overhaul it for her.

The engine was a mess internally, and I am now wondering if the heavy damage (flatten cam lobes, ground up lifter bottoms, heavy rocker arm wear, and an oil pump full of filings, etc, is perhaps a result of something more wrong than the final overheat that my friend said occurred.

The piston ring groves were slopped out worse than any I have ever seen, and this couldn't have happened in the final overheat. This engine had been in trouble long before the final, supposed overheat, which leads me to the question, "could a too cold (160 degree F), thermostat have been a contributing factor?"

After highschool (circa 1959) I worked on cars for a few year and have had experience with some 160 degree thermostats (some customers insisted on them), and how detrimental they can be to the life of an engine---coking things up, due to the poor combustion.

Why does the Haynes manual call for a 160 degree thermostat in this engine---then? After all, Haynes got their information from the manufacturer, and did not the manufacturer do the proper thermal profiling of the engine?

Anyway, you fellows have convinced me to install a 180 degree stat, but what about the blanking sleeve?

Where do I buy one? I guess I could make one at my friends machine shop. Are a lot of people using these sleeve?

I do have several T/C temperature meters and could do some thermal profiling, but I was hoping to not have to turn this overhaul into an engineering project.

Thanks for your views.

Layne Wilson
Layne Wilson

Available from the usual places. Moss, VB, etc.

I've only ever seen the recommended for use if the is no thermostat installed. I'm not saying they won't work with a thermostat, just that if there's no thermostat installed then a blanking sleeve should be installed.

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29828&SortOrder=1

TTFN

Derek Nicholson

Layne

Blanking sleeves do not provide a fast warm up.

I also find the history interesting and this from a former owner

I did my Engineering training - six years - with BMC - in NZ and in England (Stewart & Ardern, "The Vale" Acton - 1962-63)

The export prototype Mini was my first development project in NZ in 1959
The tragedy of BMC was the lack of funds for refinement and, in the end funds were taken from the very viable Leyland Trucks Division to support the cash hole in the Car Division. However that was long ago and far away

oil changes on the Mini were done at 1000 miles without fail - but they leaked SO much anyway it probably didn't matter much!
The OCI for other BMC engines was 3k miles max. and Castrolite (20w-20) or Castrol XL (20w-30) were the most common lubricants. Mobiloil Special 10w-30, or BP Visco-static were "not good" in these engines in the 1950-60s!

It is also interesting to note that engine life in cold and hot climates is very similar if the Manufacturers servicing advice is adhered too. Therefore, similar cars starting from a base low (cold) of -25C and +25C will almost always have the same engine life other factors being the same. Does this suggest that the design of the cooling system (for quick warm-up) and the Engineer's designed core temperature have much to do with the engine's ultimate life?



When the Mini came out in 1959 a specially formulated oil was required Duckhams 20w-50. It was the first "heavy" multigrade - 10w-30s had been out for years. You could use the same oil viscosity today in the same engine without an issue of course. We used 10w-30 20w-20, 20w-30, 20w-50 and mono HD oils in BMC "A" "B" and "C" series engines around the world in various markets without problems - as you could today. We got very good engine life at that time.
The '74 MGB I sold a couple of years ago ran well on 15w-50 and 5w-40 synthetics - the 5w-40 wasn't in the Handbook but met the original viscosity "intent" of the Handbook
The engine felt better on the 5w-40 though


the "intent" with the B series engines was to run as I recall 20-20W (Castrolite) or 20w-30 Castrol XL. We also used HD30 oils such as Delo etc. Later this included 20w-50 as these oils became available. We used 10w-30 too and had exceptional engine life with all of these mineral oils if the car was serviced reasonably well. I know of one doing well over 300k miles without work (except for a water pump as I recall)

The availability of synthetic oils changed all this
Paul Wiley

I live in a cold climate where winter temps are often in the 20s or much below. In all the years running with the blanking sleeve and t-stat as outlined above, I have never noticed a significant difference in warm up times between summer and fall. The engine hits operating temp after about a mile on the road.

I believe the difference in experience between my car and some others in similar circumstances is that I always use a blanking cover over the oil cooler in winter. I had done this even before using my preferred blanking sleeve/t-stat combo because it became quite apparent that something was prolonging warm up until someone on this BBS suggested that I use the oil cooler cover. Once I did that, warm ups became pretty close to what they are now, and changing to the blanking sleeve/t-stat combo seems to have done little to change the warm up time since.

Just my experience, but for me it has worked out fine.
Bob Muenchausen

As has been said many time the thermostat does not control the upper temperature, only the lower.

Also a blanking sleeve does not bypass the radiator, it restricts flow through the engine and radiator to a rate similar to a fully open thermostat. This reduces the chance of turbulence and localised overheating which can happen with the high flow rates that can occur when a thermostat is removed. As such a blanking sleeve will always result in *longer* warm-up times, which is not good, as coolant is circulating through the radiator immediately the engine is started, although in localities with high ambient temperatures this may not be an issue.

The factory fitted various stats over the years, originally 180F with 165F for hot climates and 190F for cold, then the 165F became standard with 180F for cold climates. Then the 180F was reintroduced as the standard and remained so to the end of production, with the 165F and 190F alternatives. My Haynes states this although in less detail, with no mention of a 160.

The different ratings take into account the different rates of surface cooling from block, sump, and even hoses, in different ambient temperatures. I don't think it was ever normal to change between winter and summer stats by the time the MGB was produced.
Paul Hunt 2

Paul Hunt

Paul Hunt says, "Also a blanking sleeve does not bypass the radiator, it restricts flow through the engine and radiator to a rate similar to a fully open thermostat."

Question from Layne, "Paul, are you speaking here of only with a blanking sleeve installed, or both a blanking sleeve and a thermostat, which is what I was considering doing."

Layne
Layne Wilson

As I read Paul's comments, Layne (not trying to speak for him) I believe he is referring to the practice of using a blanking sleeve by itself as has been common in racing and is part of the factory competition suggestions.

As I use the blanking sleeve AND a T-stat together, my theory (and it is only a theory) is that I get the benefits of OE T-stat with its blanking ring which does pretty much what the blanking sleeve is supposed to WHEN THE ENGINE IS WARMED UP (not "shouting", just the only way to provide emphasis on this BBS) while getting a decent control over coolant temp by using the Balanced T-stat WITH it. For me it works, for others it seems a problem during warm up. If you go to Moss Motors catalog you will see that they have recently introduced a T-stat made very similar to the OE type used when the B-series engine was introduced, prodded, I am sure by those who want the best functions and results of the original design. You pays your money and takes your pick.
Bob Muenchausen

Layne-
160 stats are a relic of alcohol based antifreeze, still in use in the 50's and early 60's. The alcohol boiled off at 180, so you couldn't go that high, and it was necessary to keep track of concentrations in the system, as it evaporated off slowly even below 180.
Best is to run a 190-195 all the time, for reasons of keeping the oil dry. The car will always run at a somewhat warmer temp when loafing, but will cool more efficiently when hot and loaded. The condition of the engine you describe is a result of lubrication failure, caused most likely by cold running and lack of oil changes, possibly exacerbated by episodes of overheating. It's pretty common for poorly maintained cars to suffer from both lube and cooling troubles.
FRM
FR Millmore

This thread was discussed between 15/09/2006 and 24/09/2006

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