The_Terran

So I recently installed a new tstat, since not only was my old one opening at 120 Celsius, but I've been having cooling issues.

Symptoms: Coolant loss due to overflow container becoming full and coolant spraying all over. As a result the engine gets hot.

Initial Prognosis: Coolant was boiling, creating pressure, and boiling over causing loss and overflow. Well, I was right about that, and replacing the tstat makes the coolant no longer boil over.

Current state of affairs: Coolant is still filling my overflow and spraying, but this time just because it's pressurized. It's totally cold when it squirts out, not even remotely warm, and the gauge inside indicates the tstat wouldn't even be open by this time...So I'm getting back pressure afaik...Someone please tell me I'm wrong and that it's not a cooling jacket gasket that's gone bad.

The car was recently drained of coolant, had the engine and rad flushed as best I could with a garden hose, (Fluid came out sparkling clean) and reassembled today. My first question is: What can cause back pressure from the engine coolant intake/housing water jackets to the rad, and how can I tell definitively it's a gasket in the housing?

And if I'm right...Is it detrimental take the engine apart to replace those gaskets without rebuilding it? (I CANNOT afford a rebuild right now)

PS: A thought just occurred to me...could the water pump be pumping the wrong way? The last guy that owned this car was a moron, and hired equally stupid people to do his repair work, so I wouldn't rule it out...But is it possible/has anyone heard of something like that causing this?

PSS: If I wasn't such a masochist there's no way I could love such frustrating cars.

djessence

i dont think your water pump can drive the wrong way because its belt driven and the pulley can only go on one side.......so no it cant.

Did you properly flush the air out of the system? If you didnt, you should.

You can do a rebuild and just replace gaskets, but i dont think that will solve this particular problem, that is usually for leaks. You just have to be uber careful when dissassembling it to ensure all the pieces and seals go back in the exact ame sport and way they came out

bugman1973

pump only goes on one way. but i am having this same problem on mine cant figure mine out either.

bugman1973

how do you flush the air out. im confused

djessence

If you have emptied any coolant, chances are you have gotten air in the system.

For the most part it is a closed system where air cannot escape so you need to allow it to escape

First MAKE SURE the car is COLD!! If you dont then you will spray coolant everywhere and its usually hot

Remove Rad cap, start car

Run Car till operating temp, t-stat opens, coolant starts to flow. Bubbles will flow out of the cap. May have to add coolant cuz it wont suck it from the resevoir under these conditions

*sometimes helpful to put a funnel in the filler spot to avoid spillage when the bubbles come out.*

Squeeze the hoses a bit, let it run for awhile. Usually takes awhile to get all the bubbles out

Stop the car, replace rad cap and make sure resevoir is at the correct level

AND cooling system flushed

Siraniko

iTrader: (13)

rule of thumb:
Increase in temp on freeway speed = clogged radiator
Increase in temp on stop and go = bad t-stat or clutch fan
Loose of coolant when hot (filling up the reservoir) = bad radiator cap


Clogged radiator cant be fixed by flushing....YOU NEED ROD OUT period.

djessence

Depending on how empty the system was, may help to turn heater on high to get those bubbles back out too, though this will prolong the procedure because it takes heat from the coolant and takes longer for it to heat up.

^that tip i must give credit i found in the archives

EDIT: Very true wacky, i am just providing a method to them on how to get the air out of the system.

Also if you havent replaced the rad cap you should probably do so anyways, they are like 7 bucks and then you can rule that out.

there are ways to check your clutch fan i just cant remember how, probably in the archives (if you find thats the problem head over to the FS section, people always have em for sale for cheap me included) --> way cheaper than a new one from mada or the alternatives

steve84GS TII

Coolant pushing out of the system when the engine isnt overheated is a pretty sure sign of a blown water seal.Its caused by compression gasses entering the cooling system and bringing the pressure above 14-15psi.Since the pressure in the combustion chambers is 100's of pounds,this can happen very quickly,even when just idling.
Thats exactly what my old S4 engine did.It never overheated,but it would push out coolant anytime it was run.Id have to refill ever 10 miles or so to keep from running out.It was an old junkyard engine and had obviously been neglected and overheated by the previous owner.
A rebuild is the only cure.Provided the housings arent pitted and corroded,its just a seal rebuild.But if the engine has been overheated in the past,the housings can be warped and/or ruined.

The_Terran

Tstat and clutchfan have been eliminated as possibilities. Rad cap is new but is a 16lb one...shouldn't make a difference...

Tomorrow I'm going to try getting any more air bubbles out, in case I didn't do a good enough job today. But if not that what could it be?

Is it even possible for compression to leak into my cooling system and cause back pressure?

The_Terran

Ugh, not what I wanted to hear, but helpful none the less.

Thanks.

Vashner

There are couple of brands of aftermarket thermostats that don't work right.

bliffle

You need a tstat with the small hole and diddle stick, and the diddle stick must be up when tstat is installed.

Best to get your tstat and radcap from mazdatrix. to avoid inappropriate ones.

When refilling system with coolant leave cap off and observe coolant thru open neck. Bubbles will come out, water will stream by without erupting. You can rock car slightly to encourage air burps. Add coolant as necessary. Open heater valve, too. Let operating temp come up to normal so that tstat is open and full flow occurs.

You might want to get an infrared remote temp sensor (about $30 at harborfreight, $50 on ebay) to check for local hotspots.

djessence

Mazda dealers also sometimes carry the t-stats and they are only about 8 bucks, even from them

steve84GS TII

Yea,unfortunately its sounds like the case.

Water pumps alone cant pressurize the system beyond operational.Being centrifugal rather than positive displacement,they can be deadheaded and still not overpressurize.They will thrash and cavitate,but the water wont go anywhere since the impeller/voulute tolerances in most centrifugals are relatively loose.
Heat, causing the water to expand, is why the system pressurizes up to 14-15psi when warm.When or if the engine overheats and the pressure goes beyond that,the cap will open and relieve the excess pressure.But the momentary drop of pressure results in a flash boil of the superheated water,and the stereotypical "steam from under the hood" breakdown on the side of the road.Even if the thermostat is bad,the temp gauge sending unit is located before the stat in the cooling system,so it would indicate an overheating engine long before the cap popped.And yes,I also only recommend factory Mazda stats.

If the engine isnt "HOT", as in overheated,then there is really no way for coolant to be forced out from under a good radiator cap,except for from combustion pressure entering the cooling system. Air pushing coolant out past the radiator cap under force, is not the same thing as burping trapped air from a stubborn system.Both can cause overheating,but if the engine is cold/warm while this is going on,then it cant just be a burp issue.