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Re: Cooling Temp Fluctuation
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bnmotorsgt
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Jan 10, 2010, 7:34 PM
Post #1 of 7
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Re: Cooling Temp Fluctuation
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I have a '94 Mazda Protege 1.8L SOHC with the same problem. I started with an OE 192* t-stat. The gauge fluctuated on the top end of the scale from about 3/4 to full hot. Changed to a 180* and still fluctuated this time only about 1/2 to 7/8. The radiator is not restricted and I have good heat inside. I'm leaning toward a "lazy" temp sender. Any ideas?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 11, 2010, 12:34 AM
Post #2 of 7
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94 Mazda Protoge 1.8 temp fluctuates
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You jumped on an old thread unrelated. Lazy to just say same issue and we should read the whole thread? Not!
Guess - your radiator is NG,
T
(This post was edited by Tom Greenleaf on Jan 11, 2010, 12:38 AM)
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bnmotorsgt
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Jan 11, 2010, 5:47 AM
Post #3 of 7
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Re: 94 Mazda Protoge 1.8 temp fluctuates
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Sorry, I think you have a wrong thinking. Rad was checked by a reputable radiator shop and it's fine. Is it wrong to comment on issues that I have concerns with? The subject was already out there so I replied to it.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 11, 2010, 9:49 AM
Post #4 of 7
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Re: 94 Mazda Protoge 1.8 temp fluctuates
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Sorry if short with you - takes hours to read post by the hundreds - please forgive.
If you have good heat that's a good sign so far. Boiling coolant won't produce heat - odd but true!
Waste the $$ and get an infrared touch-less thermometer if you suspect bad info it would read right engine temp at the thermostat's rating ( usually 195F or so) at its cover at engine.
Thermo thing is $14.99 at Radio Shack plus a freaking $5 battery but neat thing. Try it in ear and get your body temp though not for that.
OK: A car without automatic climate controls should blow heat at roughly 10-15F below actual engine temp and can vary wildly by makes and models.
All things in order temps don't fluctuate with everything working once warmed up at near all extremes.
This car should have thermostatic electric fan(s) and you should feel warm/heated air leaving radiator when they are on. Careful in doing that of course.
Somewhat rare but water pump's impellers can fail to pump adequately. As said - rare. Radiator would be not throwing off heat and most likely heater would not be so good so I don't think that's it for now.
Lots of things can cause temps to fluctuate and need to rule out stuff one by one. A head gasket early on in failure could be the cause. Air (exhaust gasses) in minor amounts can cause erratic temps. Test strips for gasses in cooling system would tell or pressure build up fast upon cold start is telling of that as well.
Possible that sender isn't right. In a career I find they either work or not but not erratic - who knows?
As said - get some real temp readings, know coolant is full not just the recovery tank but at the radiator - cold check w/o pressure in system!
T
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 11, 2010, 9:51 AM
Post #5 of 7
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Re: 94 Mazda Protoge 1.8 temp fluctuates
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That's the one I use,
T
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bnmotorsgt
User
Jan 15, 2010, 8:15 PM
Post #6 of 7
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Re: 94 Mazda Protoge 1.8 temp fluctuates
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T,
Gas test in coolant was good. Head gasket OK. Dealer installed their t-stat but still have symptom just at a cooler temp. Will get the thermometer thing you talked about and get a good temp reading. The only thing I can think of now would be the sending unit or water pump. Even though I flushed the heater core and have good heat inside, could the heater core cause this issue? Thinking about bypassing it and see what happens...
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 16, 2010, 2:40 AM
Post #7 of 7
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Re: 94 Mazda Protoge 1.8 temp fluctuates
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Damn!
This is the thermometer - can be had elsewhere too..........
Last seen was ~$15 + a $5 battery. Handy thing to own no matter what.
Just measured - it's only 4" long and you need to play around with it as it can
screw up. Try an ice cube at home - hot coffee and so on. It's not for medical
use but if pointed in your ear real close comes dang close to real body temp!
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The heater core by-pass can be done with just the right plumbing or even a deep socket that allows flow thru temporarily as a test.
I don't know the exact engineering of every engine ever made but some are using the heater core as part of evening out internal engine temp year round - aka - part of the by-pass system as already discussed. Generally the heater hoses are two different sizes - the inlet being smaller of the two.
GO EASY ON THE HEATER CORE AS NECKS CAN BREAK! Perhaps route another hose from the source ends at engine instead of messing with the core. Plain worm clamps should do to squish hose that's a tad to big to a smaller spud (inlet/outlet necks.)
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Before you even do that test the housing of the thermostat - AND upper vs lower radiator hose for temps.
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Refresh: Water pump is always working whether thermostat is letting coolant out to radiator or not. The idea is uniform engine temp AND keeping the flow to thermostat uniform so it will open as needed - no more, no less.
Note: Antifreeze is a lousy coolant. Some folks think the more the better - not so. Don't exceed 50% which (test your tester) which should be -34F. Some hard working engines will say set to no more than -20F as it works better but needs changing more for the anti-corrosion properties needed too.
One more for now: If heater core was once plugged the water jackets of engine could be full of junk and hard to flush out - hope not. Most engines have plugs at lowest point of engine block to drain out last bit. If that's in the cards and you are sure you have the correct plug(s) frequently you need a short piece of wire as they won't drain as junk is plugging them. (Did a ton of marine work and this crap is seasonal here!)
I give you credit for pursuing this. Not everything is easy and this is already testing techs that mostly won't have endless time to check everything. Hard to know if water pump impeller is working/corroded without taking it off.
Hang in there,
T
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