is there such s thing as a "..high performance thermostat.." (or is it called
something else) ?
just finished a total engine build, machined heads, all new internal parts
have normally run without a thermostat due to increase in engine temp
in case it matters, car is mazda mpv and asking at the dealer parts depot just
don't even know where to ask so if anyone knows of a place, please post url or
just gets me
not really. thermostats sold as "high performance" are generally just
lower temp thermostats which are a band-aid for too-high compression
and/or insufficient cooling capacity.
That said, if you can find a Robert Shaw "fail-safe" thermostat for
your engine, those are a nice upgrade. They're a higher quality than
OEM and typically don't fail stuck closed. I'd stick with the stock
temp rating though.
Ask the guy at the parts store if they have a thermostat that opens at a
temperature lower than stock. He should be able to tell you since these
parts are sold by the temperature at which they open. High performance
thermostat sounds kinda goofy. A super high performance thermostat would
be one that opened when the engine is cold. :-)
And be prepared to get crappy mileage and likely wipe out the O2 sensors
A thermostat in most engines does more than regulate water temp, it also
regulates flow. The restriction in the system keeps the water in the
engine longer to absorb more heat and make sure it gets into all the
passages. Without it there are places that will develop steam pockets
which will cause you a lot of problems.
But it's your vehicle....
"nick" wrote in
Then you have a deeper problem with the cooling system. Removal of the
thermostat is masking that.
The cooling system is one automotive system that has remained fairly simple
over the years, even as other systems have become hideously complex.
Troubleshooting is easy.
No modern Mazda or any other modern Japanese car should have ANY trouble
exhausting engine heat with the standard OEM thermostat provided the rest
of the cooling system is in proper shape. Do not try to do a bandaid fix
with the wrong thermostat, but correct the underlying problem instead.
This engine, like those in all modern Japanese cars, uses a high-flow, low-
heat-transfer cooling system. Coolant is meant to speed through the system
quickly, but not /too/ quickly. /Too/quickly means overcooling, excessive
emissions, and severe engine wear. Not quickly enough means overheating.
Check for these things (besides external leaks and a blown head gasket):
- Evidence of actual overheating (need to rule out faulty gauge; infrared
- Radiator that's internally plugged
- Radiator with fins corroded away
- Radiator with fins coated with gunk such that air cannot pass through
- Radiator fan not operational, or starting up too late
- Block water jackets that are silted-up due to incorrect coolant or
insufficient fluid changes
- Aftermarket thermostat (these are usually inferior to the OEM that comes
with Japanese cars, which is usually the excellent-quality ND brand)
- Water pump with loose impeller (don't laugh; I've seen this with
- Aftermarket hoses, which can collapse under suction
- Excessively advanced ignition timing
- Excessive carbon buildup in combustion chamber (guess you've dealt with
this by now).
all internal gaskets are brand new (felpro)
no evidence. power output increased due to size of bore, machining of heads
brand new radiator installed.
pressure test performed after installation, all parts are new
new water pump installed, better than OEM
uncollapsible coilwire supported hoses installed.
timing is set perfect according to computer tests, chamber is so clean you can
fresh rebuilt engines may run hot until everything breaks in. perfectly
normal. Worry if it's overheating with a stock thermostat after a
couple hundred miles, and try not to drive it during break in where it
would be likely to overheat (e.g. don't drive it where you're likely to
be caught in stop and go traffic.)
I second all the responses to use a stock temp rating thermostat and not
worry about it.
"nick" wrote in
Nevertheless, if you've done all that work, the cooling system should now
be in tip-top shape.
A modern Japanese cooling system has a tremendous amount of heat-exhaustion
capability and should be more than able to keep up with bigger bangs in
Put a new OEM thermostat in there and see what happens. I'd also recommend
a new OEM rad cap as well.
The comments and items listed by Tegger are accurate and thorough.
For what its worth, in 1982 I had an old 1966 Dodge slant 6 that overheated.
I installed new "everything" in an attempt to fix it.
The problem was solved one day when I had the radiator cap off the new
radiator to check coolant level because of overheating, --- the sun was
shining at just the right angle to illuminate the inside of the new radiator
and the top of several of the tubes. The tubes in the NEW recently installed
radiator were plugged with small calcium carbonate pieces that had been
breaking off inside the block. This was due to the radiator cleaner I had
used when I first began. As mentioned the engine was old and had likely
been filled mostly with water that had a high mineral content.
I had the new radiator rodded and bought a sieve at the hardware store,
removed the stainless screen and made a funnel that would fit inside the top
return tube of the radiator, pointed end into the radiator. I made sure the
screen would not get pushed in too far (bent a few of the screen strands
back over the radiator tube and then pushed the hose back on. Later I made
one for a different car and just made the filter screen long enough to touch
the oposite side of the radiator.
At first I checked it daily and would remove all the little pieces of
calcium carbonate. As time went by fewer pieces showed up and after a few
months it was clean. I left the screen in and would check it every two or
three months just to be sure. I sort of remember leaving the screen
unchecked one time, and waited untill the engine began to run warmer than
Though its not really necessary I have since used distilled water instead
of plain old tap water with antifreeze, in all my subsequent cars, about
I am 67 and rebuilt my first engine from a 1940 ford when I was 14 in 1956
but have not worked in the automotive industry, only on my own cars or
Good luck- hope this might be of use