overheating problem.

[mx-6er]

I drive a 91' Mazda Mx-6 and recently been having a serious overheating problem. It's so frustrating because almost everything imaginable has been replaced, such as new radiator, new fluids, and water pump, and the super puzzling thing about it is that i am not even running a thermostat so it should have a constant flow, but I have no idea what is going on. I have heard that if you have a blown head gasket that might be some of the problem, but anyway I really need some help its my only car so please help.

[Skaterkid]

Most likely a HG or maybe an air bubble. Have you checked compression or done a leak down test? Is it eating coolant? White smoke out of the tailpipe?

[mx-6er]

i have not done a compression check, nor do i even know what a leak down test is, it does not eat coolant its always full, and never smokes out of the exhaust. thanks for the help. anyone else?

[Martian]

Is your coolant discolored at all?

[boostedEG]

the thermostat is probably your problem... because it is constantly flowing the coolant is not staying in the radiator long enough to cool down. put one in and see what happens.

[Slow96GSR]

You won't really over heat with the thermostat out. It never stays in the motor long enough to heat up a lot. Been running the A/C much, stop and go traffic, running it while stopped? If yes then stop that's a good reason your over heating. If you never use A/C and aren't in stop n go traffic could be something serious.

A leak down test is when you hook up a gauge set to each cylinder at TDC and put compressed air in. Then it shows you the PSI and what percent of that is leaking. A new/rebuilt motor should have less than 3-5%, a old/ beat motor can have up to, my standards, 10% total blow by and 10% difference between cylinders, at most, and that's when we rebuild.

General Comp test and LD test: http://www.wcengineering.com/articles/leakdown.html
For turbo: http://www.geocities.com/dsmgrrrl/FAQs/leakdown.htm
Non turbo: http://cybrina.mine.nu/MR2_Docs/leak_down_testing.htm

[boostedEG]

i have overheated without a t-stat, in 3 different cars, it just doesn't happen very quickly, the temp slowly rises higher and higher.

[mx-6er]

it overheats, in any situation, stop and go, highway, stopped, i do not run a/c at all. i think it is a head gasket, the coolant is not discolored at all, so i really do not know.

thanks for all the info slow96gsr, and i might have to try putting the thermostat in since it does take a while to heat up like boostedeg said, but i always thought that since the thermostat was out there would be a constant flow, keeping the coolant cold enough to keep the engine cool enough but not sure, gotta try something here real soon.

[Martian]

If your coolant isn't discolored at all your head gasket is most likely okay. You most likely have air in the system. Your thermostat regulates flow. If the coolant is going to quickly through the system, it won't be in the rad log enough to cool down.

[riceburner700]

have you tried a different radiator cap?

[mx-6er]

I am beginning to think that it is the thermostat, and no i have not tried a new radiator cap, although the radiator is new and all.

[ryanman]

Try installing a t-stat, running without one can cause it to overheat just like the other guys said already. A blown headgasket won't always cause oil to get into the coolant (or coolant in the oil) but it can pump air into the system but also if that was happening your radiator hoses would've already went bye-bye from all the air pressure.

[HONDA GHANDI]

Have you actually measured the temps of the coolant and radiator hoses to see if it is your gauge that is bad? What are the actual temps we are talking about here?

[mx-6er]

i put a thermostat in today and ran it for a few minutes, still overheated. as for the actual temp readings i do not have anything to do that, but i can tell you that when i do get it hot and shut it off i can hear the coolant in the resevoir bubbling/boiling. I am stumped.

[boostedEG]

hmmm.... air pocket then?
do you see any bleed screws any where in the cooling system?

they are usually brass, and usually found on the water necks. there can be a ciouple of these.

[boostedEG]

unless you overheated it really bad then i doubt you blew a head gasket, but there are test kits for that. im not sure how accurate they are however, maybe someone else can chime in on them.

you basically put a blue fluid into a tube thing and press it onto the waterneck on the radiator, and if it has a blown headgasket the air/fumes coming out of the radiator will have exhaust fumes in it that will turn the fluid green or yellow or something like that.

[Civic-8442-]

get a HONDA and you wont have problems with no answers

[Skaterkid]

get a HONDA and you wont have problems with no answers
LOL......

When it comes to these things any car would be getting the same responses. I say if you're this stumped take it in and get compression and leakdown tests.

[mx-6er]

i do believe it is a head gasket, because i did overheat it really bad when it first did, it cracked the radiator along the top because of the pressure.

i do have to agree waldo, i do wish i had a honda, no doubt.

does anyone have the guage that i might be able to borrow to do a compression check? i would appreciate it. How much would a leak down test cost?

thanks for all the help guys.

[Martian]

Just a thought but a new water pump might be in order here.

[mx-6er]

it has a brand new water pump in it replaced last monday, read the thread.

[mx-6er]

ahh yeah, a good idea, although i just did it a week ago.

[mx-6er]

and i replaced the head-gasket yesterday and it still overheats.