WonkoTheSane

iTrader: (2)

Yesterday I had an almost heart-dropping experience.. I thought I had blown a coolant seal... But things weren't jiving with what I was expecting of that: (For those who don't care about the story, feel free to jump down to the question).

Symptoms:
Massive buildup of coolant pressure
leaking coolant that was running down around the front of the tranny bellhousing when the engine was on.
No smoke, noticeible steam
My engine temps got up to nearly 3/4 of the gauge (well below "H")

It turns out that hose that runs to the UIM (upper intake Manifold for the n00bs ) from the engine block cracked on the block side. and was causing it to leak out onto the top of the block when it was under pressure..

After replacing the hose, I started the car with the "coolant fill cap" off, so i could make sure I got the air out of the system.. .It stopped the leak from the back side of the engine, but after the car started to warm up, I got LOTS of coolant gushing out of the fill cap... . WTF???

After letting the car cool down, Dad and I took the thermostat out, at his insistance.. My thermostat is a Mazda OEM one maybe 4 months old at the oldest.. After we put it back together, the car ran great. I didnt' see it move above 1/8 of the guage at all yesterday.. ( no runs, just running in the garage).

Today, on my way to work, it didn't really get to far above the top "C" line, at most 1/8th of the guage..

Here's my question - Is this bad for the engine? Dad said they always used to take their thermostats out once spring hit, (he's an racer from way back), and that "Real sports car drivers left theirs out in the winter, too (mockingly)". Other than not getting heat in the cockpit, is there any disadvange to running without the thermostat?

SureShot

The thermostat in our rotaries has a second part - a spring loaded disc tha extends below the stat.
It's job is to cover a bypass port inside the pump housing.
If that port is not covered or plugged, much of the hot coolant flow from the engine will recirculate & give symptoms like a partially blocked radiator.

Froggmann

As for the running cold question your going to have a problem with carbon building up inside the engine and if your state still requires smog your less likely to pass.

WonkoTheSane

iTrader: (2)

SureShot - What are the symptoms of a partially blocked radiator? I always figured that it would lead to higher temps, not lower?

Froggmann - Luckily, PA only requires a visual inspection (for now), but the carbon build-up thing is enough to make me get another thermostat later this week..

thanks guys!

RETed

It's not a clogged radiator.
If it was, it'll still be overheating.

Running without the thermostat will cause the car to run cooler.
This affects mileage.
I don't think you're stupid enough to run the car hard when it's freezing.

I would at least "core" the thermostat and put back the "flange".
If you're revving the motor close to redline, the coolant gets all confused, so put the flange back in at least.
If you're constantly revving close to redline, it's recommended to plug the bypass hole in the water pump housing.


-Ted

WonkoTheSane

iTrader: (2)

Thanks for the clarification ReTed, I'm glad you have enough faith for me to wait a bit to gun it, too (I always do).. I think i'm just going to get a new thermo from mazda again, but I'll have to wait until later this week *cough* payday*cough*, since school $$ was due on monday...

SureShot

I'll saya it a different way.
Without the stat, the bypass port is left open, so close to half of the coolant flow never goes through the radiator, and you will tend to overheat in hot weather.

If you must remove the stat, then you must block the bypass port in the pump housing.

alwayssideways

as for removing the Thermostat in the "old days" they used to run straight water in the summer and the normal 50/50 mix in the winter. Atleast thats what my teacher told me.

SureShot

The "old days" were before aluminum engines.

The corrosion inhibitors in antifreeze are essential to protect the engine at all times.

gnome311

I always remove my thermostat in the summer months, and have never had an overheating problem. But just the same, where is this bypass port?

WonkoTheSane

iTrader: (2)

Dad never said anything about running straight water.. just removing the thermostat... of course, his racing was british and jap sports cars (MG's and Nissans) and bikes, not really the big american iron...


I'm definatly going to take a look into this bypass port thing, though... This isn't a s4/s5 kinda thing, right, it's there on both?

SureShot

On both S4's & S5's

When you take out the stat, look down in the pump housing, about 1" under where the stat flange sits.

Then look on the bottom of the stat & you'll see the spring loaded disc that covers the bypass hole.

The S5 cooling system has more head room so you might not notice the bypassing until conditions get more extreme.

SureShot

On my '87 the limits were sustained 90 MPH, 90 degrees, 90% RH, AC on.
I called it "hauling ice".

Above that I got "temp creep"

On the '91 the limits are higher, but I have yet to find them

RETed

We're running several of them here in Hawaii with no overheating problems in normal street driving.

On the track it might be a different story, but for street use, it doesn't seem to cause a problem.

We do "core" the thermostat and put the flange back.

I've run my car through Sac and Vegas summers over 110F, and it never bats and eye.


-Ted

sirx7

i heard for not leting the engine warm up to normal temp u will has loss in hp numbers taht is why u don't want to have cold engine you always would prefer to have a constant 180

SureShot

That's why.

The racers around here tap & plug the hole.

NZConvertible

Why not just put a new thermostat in so the cooling system works like it was designed to?

RETed

Cause there's a chance the thermostat can go bad?

I did it cause I was trying to troubleshoot an overheating problem at 2am in the middle of the night.
I did not have another good thermostat handy.
I just cored the original thermostat I had.
I never bothered to replace it.

I do run an SPI electrical water temp gauge.
I watch it like a hawk all the time.
Other than slower than normal warm-up times, the car runs fine and does not overheat.
In Hawaii, there is no worry about anything close to freezing temps.
Why bother paying for something I don't need?
The car might be drinking more gas, but it's getting 17mpg on mixed driving.
I feel nothing is wrong with the car at this time.


-Ted

gnome311

I pull mine because I don't want to let a $5 part, cause $1000 in damage. I had one stick in my old gsl-se, while cruising the xway at around 90 or so. If I wasn't constantly keeping an eye on my temp, I woulda been screwed.

NZConvertible

There's a chance any part in your car can go bad, some with costly consequences, but the chances of losing an engine due to a new thermostat failing to open are extremely low. This is no excuse to not use one.

In normal driving the engine will be running cooler than it should be. If you actually think that's good for the engine, then whatever...

BTW, ambient temp has little bearing on this. An engine running too cold (say 70degC/160degF) is still far hotter than ambient temp will ever be.

RETed

Eliminating one more possibility of failure is a plus in my book.
Like I said before, I did my mod in the middle of the night.
I've just been lazy to replace it.
The car runs fine without it, so why bother...

[QUOTEIn normal driving the engine will be running cooler than it should be. If you actually think that's good for the engine, then whatever... [/QUOTE]
The only time it runs cooler than normal is the initial warm-up time.
Other than that, the engine will NOT go below 180F, according to my water temp gauge.
Even with the electric fan on all the time just idling and sitting in one spot, the temp does not go under 180F.
The car basically runs like it has a thermostat in it with the exception of the initial warm-up time.
I get good gas mileage, so I see nothing wrong with what I'm doing.


I noticed that under real cold ambients - down to 10C or under 50F, the water temps do go under 160F on the gauge.
Like I said before, I do not see temps like that in Hawaii, so it does not concern me at this point.

Why are you so adamant against this?
Have you ever tried it?
It sounds like your argument about the steering wheel spacer - I bet you never done it, and your idea of the whole subject is downright wrong...


-Ted

NZConvertible

Yeah, actually I have. I bought a car that turned out not to have one because the PO was silly enough to think he didn't need it. The car ran considerably better once I fitted one. While you might get a way with it in Hawaii, many people on this board live in far milder climates. If it works for you that's fine, but don't post here that running without a thermostat makes no difference without making it quite clear that most people will see negative effects. This is another one of those "if it wasn't needed it would be there" things. And yet every single engine made still comes with one.

Dude, this should not require explation. Like I said, it's simple geometry. I'm quite tall, so my line of vision to the gauges is at a higher angle than the centerline of the steering wheel, which is in it's highest position. This means moving the steering wheel towards me moves it further into my view of the gauges. Explain why I'd want that...

RETed

I've also run the car in Sacramento, CA and Vegas winters down to 0C or 30F right around freezing.
The car does the same thing, but it will cool down to 160F if I keep the fan running at idle.
The car doesn't run any worse or get noticably worse gas mileage.
Of course the warm is significantly longer with such cold ambients, but the gas mileage still stays around 15mpg or better.
I don't see any significant negative effects, but I do not recommend doing this in such cold climates.


You're taller, which means you should be leaning back further.
I sit with less than 2" of space between my head and the headliner / sunroof.
With a helmet on, I constantly hit the headliner.
If you're sitting that much higher than I am, you're in a bad driving position.
If you're sitting that much higher, the top of the windshield should be blocking parts of the road!
The only way the spacer is not going to have any effect for you is if you sit in a bad driving position, or your in-seam is like 40", and you have a very short torso.
So which option is it?



-Ted

WAYNE88N/A

You guys....lol....

What about the thermo sensor? Won't it take much longer to "tell" the ECU that the engine's up to operational temp with the t-stat out? The coolant's flowing past it as soon as she's started, instead of sitting there and warming it up until the stat pops. Won't this cause her to run rich (in the "cold" mode) far longer than necessary?

Some among us are also tossing the notion around that the t-stat can go bad and blow your engine without you noticing anything going on, and that's why it should be removed...Shame...Anybody that keeps an eye (or two) on their gauges will pick up the abnormal temp rise before anything causes damage...

As far as an engine running TOO cold? Within reason, the cooler the average temps are for an engine during it's lifetime, the longer she'll last. The 180*F point is where the Mazda
engineers figured she'd run most efficiently, for fuel economy, but she can run far lower than that without detrimental effects. Little bit of trivia- a modern jet engine will last forever, as long as the temps are maintained below a certain threshold, it's the excessive heat (takeoff power) that causes deterioration- same as our engines...

WonkoTheSane

iTrader: (2)

Wayne88N/A - That's what I was looking for thank you! Interesting factoi, too


To anyone else paying attention: There has been a lot of good info here, and I'm definatly not running my car in the winter (PA averages about 10-20 degrees F), and it would be a bloody long ride to school until I got heat. I was just wondering about more of summer time or even temporary detremiental effects.