B's running a tad hot

[jaybird]

Seems the hotter it is outside, the warmer she runs. Far past the N, maybe 1/4" or so.

Since we're taking her on her inaugural 'road trip' Thursday morning, dahubby (**THUD** he's working on her) wants to put in a new thermostat, there's a 195 in her now. Any suggestions? Have new radiator hoses, new fan belt, and we're getting new tires yet this week.

Not sure about size on the tires either. I know there's been a dozen threads about that, including one of my own, but I'm too lazy to hunt for them!

 

[AlamedaMGB]

There should be ton's of threads about thermostats, but it boils down to this( I'm feeling a little spicy today, so forgive me )

THERMOSTATS ARE FOR THE WINTER!!

Thermostats work to make sure the engine gets UP to the temperature rating, so that things like the oil get warm and lubricate properly, and your water choke knows to lean out the fuel mixture. Putting a new thermostat with a higher rating in only forces the engine to run hotter - Assuming that the REST of the cooling system is working properly.

Explanation follows, skip if you understand thermostats and cooling:


The thermostat PREVENTS water from entering the radiator loop in the cooling system until it reaches it's rated temperature.. Then the wax inside the thermostat expands, overcoming the spring tension to allow the piping hot fluid to rush excitedly into the upper radiator hose. The coolant then rushes down the radiator tubes, transferring as much heat to the tubes and fins, which in turn are cooled by the forceful wind blowing through the radiator. That warm air rushes past the engine block, and down under the chassis ( at speed. The engine coolant, having given up some of it heat energy, continues to drop into the lower radiator chamber, where it is whisked away through the lower radiator hose, BACK into the water pump and engine block.. It takes another lap around the engine block, then through the cylinder head passages, all the while allowing the hotter engine to transfer heat to the coolant. This hot coolant then rushes by the already open thermostat back for another lap to the radiator to exchange heat to the air.
WAIT, what happens before the engine reaches the thermostat temp? Funny you should ask. The water pump cycles water through the bypass system directly back into the engine!! the water goes around and around inside the block and cylinder head until it reaches the thermostat temp, and the above process begins.

What's this you say about winter? OK, so it's 20 degrees out, and you haven't the sense to garage your B. The engine warms up to 180 degrees, and the coolant rushes back to the radiator, cooling down to a brisk 40 degrees by the time it returns to the engine. The coolant takes a lap through the engine, and has only pulled enough temp from the engine to raise it's temperature to 160 degrees.. That fridgid water rushes past the thermostat, the wax inside stops expanding, and hte spring slams the door shut, so the hot water will stay in the engine. This happens over and over, when it's cold out.

I should take a moment to talk about the fan.. It's only useful for running around town. When you are on the highway, the air rushing in from your forward speed is WAY more air than the fan moves.. In fact, the fan actually impedes the flow of air.

OK, end explanation.


Bottom line, replacing the thermostat should only be done to keep the engine in the cooler ranges for operating efficiency, if you replace the thermostat with a higher temperature unit, you are only forcing the engine to get warmer before the radiator can do it's work. IF you put a cooler thermostat in, the engine may never warm up to the proper temperature( even on a summer day, on the freeway ) and the water choke will not work so well either. thge same goes for running without a thermostat.. Not a good idea.


Solution? Suggestion.

[*]1. Use a two part acid cleaner like prestone to flush your cooling system and radiator. A clean radiator works better because it transfers heat better. Scale in a radiator both blocks flow, and insulates the water from the fins.

[*]2. Put the proper ratio of "Anti-freeze" coolant. It transfers heat better, and most have a corrosion inhibitor in them to extend the life of your cooling system.

[*]3. Use a product called 'water-wetter' It also improves the heat transfer.

[*]4. If that doesn't work, find out exactly why your engine is running hot.. A lean fuel mixture, timing, leading head gasket, plugged oil passage, clogged radiator, loose fan belt... The list goes on.

Good Luck.

And speaking of cooling systems and chokes, my choke was still on after I drove 20 miles to work.. Guess I'll have to look at that tonight. Sigh.

 

[Stewart]

You could switch to the 165 degree T stat but if something else is causing it it's just going to show up a bit later. Also try 75% distilled water and 25% antifreeze for the summer. 100% distilled will run the coolest but will not prevent corosion. Check all of the stuff listed above as well.

For tire size for the 14" I belive its 185 70 14.

 

[MGretired]

I always use a 160 degree thermostat in the summer, 195 in the winter. Thermostat won't make any difference if system is not up to snuff. Drain (both radiator & block) & refill with water & system flush (Prestone etc.), run for 20 minutes. Drain again (when it cools). Fill & drain once more, then fill with 25% anti-freeze, water wetter & distilled water. You might want to have the radiator hot-tanked while you’re at it, takes about 20 minutes to take the radiator out; good radiator shop should charge about $75. My gage never goes above N, even when it gets over 100 degrees here in Boise. 1/4 above N isn't good, especially if you’re going on a trip!
If you choose to run without a thermostat, make sure you install a blanking sleeve (Moss, VB etc.) or you will actually make the car run hotter!
Here's a good web site that explains MG cooling very well.
https://www.custompistols.com/cars/articles/cooling.htm

 

[Steve_S]

I run a cooler thermostat to allow for additional cooling on decents, which helps prevent overheating on climbs. I'm using a 160-degree. My car typically runs around 180-degrees, cooler on the downhill and hotter on the uphill. I've found that the cooler temperature at the bottom of the hill helps prevent getting too hot by the time I get to the top of the hill. This is of course in hot summer months when the temperature is over 100-degrees. In normal 70-80 degree weather there should be no reason for a car to overheat on any hill.

 

[ChrisS]

If the problem showed up rather suddenly then I would tend to lean away from a fouled radiator. That usually occurs over time or after you overheat the engine due to low coolant level, especially with tap / hard water. It could be a stuck thermostat, but before you start changing parts check the timing. Last year before I fixed my distributor the temp gauge would climb when I was on the highway, and I knew I had to pull over and retard the ignition. It was running to much advance, but I couldn't hear it ping between the open air and exhaust. The timing would walk out on it’s own due to worn internals and I would repeat this every few days.

 

[Steve_S]

I just noticed your tires comment. On stock wheels the best size in my opinion is 175/70R14 for a good ride, or 175/65R14 for better handling. The 65-series will make your speedo read fast. Some people run 185 width but it's really too wide for the stock rim and while it will work, you will get sidewall flex. 165 is also very well suited to the car and an ideal size but your choices are very limited in a performance tire (Michelin XZX good but $$$) and not much better in an economy one. I'd take a look at British Wire Wheel. They carry a few nice tires in 175.

 

[Guinn]

Hi, Jay. I just tossed my old tires - definitely wrong size - and put on 175/65R14's. The handling is much better and so is the ride. I haven't run a speedo test yet but it seems pretty close.

Guinn