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low/high temp engine running question

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recordsj

Jedi Warrior
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With thiscooler weather my 1500 MG midget engine has been running cool. It has a180deg F thermostat. When cruising down the highway (45-55 mph), theengine will run @ around 140 to 160F. In town it will get up to 170-180F. I have already swapped out with new thermostat and engine still does samething. The radiator has a thermostaticcontrolled electric fan set to turn on @ 185F. Shouldn't the thermostat with an opening temp @ 180F keep engine at thatmin temp?
Any thoughts?

I have done apressure test of the system and the cap and it holds 15psi.

During thesummer I would be having temps running @ 200-210F (especially going uphill @45-55 mph). Typically the engine would be running @ 180-190F.
Any thoughts?

Temps have beenconfirmed with a laser thermostat.

I have madesure that the system is bled to get air out also.
 
Stuck thermostat? I'm having a similar issue with my '69 Sprite. The temperature gauge never gets up into the "normal" range, even in the middle of summer. I just swapped out the thermostat last night, but probably won't get a chance to test drive it until the weekend. Of course, I may just have a bad temperature sensor / sender as well.
 
Tested the old thermostat and the new one in a pot of water brought up to boiling, both open up 180 F. Confirmed gauge reading with laser thermostat.
 
bobhustead said:
With or without a thermostat, cool air absorbs more heat thru the radiator than warm air. Don't worry about this. Bob
Click to expand...

True the radiator will expell heat better in cool air. With that said the thermostat should close more to restrict flow since water is colder. The issue is that with the engine not getting up to proper operating temp, it won't run as efficient and the engine oil won't burn off water and other contaminants.
 
Combustion chamber temps are virtually unaffected by the described variation in coolant temp. Thermostat opening can be regarded as on/off, not gradual. You might have a tstat that is opening early, but once again don't worry about this. Bob
 
The 1500 horizontal flow radiator is really efficient at cooling, so this is not that surprising. Especially with a 185F thermostat. Many of these cars came with a 193F thermostat as standard. My 1275 race car is running a 1500 radiator and I also have issues with overcooling (at times). Overall, this is a "good" problem and is easier to deal with than the overheating problems some Spridget owners deal with when using the older-style vertical flow radiator (which can be marginal in some warmer climates). If you feel you'd like to bump up the temperature in the cooling system, simply block off part of the radiator. You can experiment with cardboard pieces first and once you've got a size and shape figured out, you may wish to fabricate a nicer-looking aluminum shield. But don't block off too much.....it's always safer to run a bit cooler rather than too hot.
 
aeronca65t said:
The 1500 horizontal flow radiator is really efficient at cooling, so this is not that surprising. Especially with a 185F thermostat. Many of these cars came with a 193F thermostat as standard. My 1275 race car is running a 1500 radiator and I also have issues with overcooling (at times). Overall, this is a "good" problem and is easier to deal with than the overheating problems some Spridget owners deal with when using the older-style vertical flow radiator (which can be marginal in some warmer climates). If you feel you'd like to bump up the temperature in the cooling system, simply block off part of the radiator. You can experiment with cardboard pieces first and once you've got a size and shape figured out, you may wish to fabricate a nicer-looking aluminum shield. But don't block off too much.....it's always safer to run a bit cooler rather than too hot.
Click to expand...

If the cross flow radiator is so effcient, why in the summer would I run temps around 210F (w/ 180F thermostat)? Or is 210 not really that hot to be considered overheating (w/ 50% mix of water and antifreeze)? This seems to be a big temp fluctuation.
 
OK, that's wierd. 210F is hot for a Spridget. All I can think of is that your lower hose is collapsing in the hotter temps (the lower hose is under suction). Sometimes, then they get old and soft, they collapse when running. The cooler temps may be keeping the lower hose ridgid enough to flow properly. Otherwise, it could be a funky thermostat, a really old fanbelt or waterpump with corroded impeller.
 
In these discussions... the correct fan belt isn't discussed... as in slipping and not getting the pump the 100% efficient rotation...
 
Replaced thermostat, issue still there.
New pump about two years ago.
New belt about three years ago from Moss.
No noticable noise from belt.
New hoses two years ago.
I guess I wouldn't discount hose collapsing (will try to see what is happening next summer when I would see hotter engine temps see with current cooler temps not seeing 210F).
 
Have we talked about timing yet? Wonder if you may be running lean too.
 
aeronca65t said:
OK, that's wierd. 210F is hot for a Spridget. All I can think of is that your lower hose is collapsing in the hotter temps (the lower hose is under suction). Sometimes, then they get old and soft, they collapse when running. The cooler temps may be keeping the lower hose ridgid enough to flow properly. Otherwise, it could be a funky thermostat, a really old fanbelt or waterpump with corroded impeller.
Click to expand...

I should add that the engine is 9:1 copression using premium gas, which maybe adding to the heat load.
 
Have you checked your air/fuel mixture on the carbs? A leaner mix will tend to run hotter, and a richer mix will run cooler (something I picked up from the guys who work on radial aircraft engines). I found that holds true with my Sprite. Now that the carbs are leaned out, I'm seeing warmer temps on my gauge, but still on the low side of the N.
 
SaxMan said:
Have you checked your air/fuel mixture on the carbs? A leaner mix will tend to run hotter, and a richer mix will run cooler (something I picked up from the guys who work on radial aircraft engines). I found that holds true with my Sprite. Now that the carbs are leaned out, I'm seeing warmer temps on my gauge, but still on the low side of the N.
Click to expand...

With the cooler weather engine is running cold, 140-160. In the summer engine was running hot 180-210. Don't think it is an issue of running rich or lean.
 
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