Thermostat or Radiator what a dilemma

[Divinehammer]

2003 Mazdaspeed Protege 100k miles
Recently I am having an issue with my coolant steaming out. It does not steam out of my reservoir. The engine never gets overheated the temp gauge is always steady at about halfway or bit under. it will only steam after I am down the road a ways but it does not steam every time in fact it has only done it 3 times in three weeks. The last time it steamed it was on my short drive to work which it was a bit cold that morning about 35F. I filled it back with the inch that was steamed out of my bucket and went to lunch, no issues. Went to go home and it started to steam on the ride home. Stopped to make a pickup and it steamed at take off but it stopped somewhere on the ride home because it didnt do it when I pulled in at home. That was all city driving I cant seem to get it to do it when I am on my hour commute on the highway, of course I wouldnt see it then but I am not dropping fluid either. When it does steam out it gets fluid all over the pan at the bottom and a few places up top but I think it is being blown up high. There is no mess arround my Reservoir. it gets on the engive of course and you can tell by the smell. the car leaves no puddles when left in the garage, overnight or several days.

I first took it to pepboys they said new radiator it failed the pressure test but I hear that losing a few pounds per over time is normal.

I took it to a radiator shop that put it under pressure and looked all over for leaks and could not find anything they had it under pressure all morning.They told me about the pressure test gradually losing pressure as just being normal.
They said I dont need a new radiator it doesnt seem to leak.

I then took it to the Mazda dealership. They are also now telling me I need a new radiator it was again losing a few pounds of pressure over 30 or 40 mins I would guess. When I took it to them it had some residue left on it from the radiator they put it up and showed me where they think it is coming from. on the bottom of the radiator there is the plastic pan that is crimped on to the aluminum part of the radiator they say that it is leaking out of that crimp. They say that it may only leak at say 68 degrees and after it gets hotter than that then the seal inside expands and fills the gap thus stopping the leak. One would think that it would do it everytime then in some form or fashion but it doesnt I can wash off the engine and go for a week and nothing happens and the bucket level doesnt drop and no residue. When we first took it into the dealership we though that it was going to be a thermostat but the tech doesnt seem to think it is that. He states it would happen more often and would come out the bucket or if it was stuck open, the car would never heat up.So if it was a bad thermostat do you think it would steam out other places instead. I mean if it was stuck closed wouldnt it then come out the seal or wherever. When it does steam I can see the steam coming from the Radiator cap, and the hose coming out of the plastic top right by the Rad cap. Additional steam comes from whatever else the fluid got on also. I have seen it only steam from just the radcap and hose fitting and just for a bit, but then other times it is all coming out everywhere.

So the main things are that it never comes out the reservoir, it never gets hot even when it is steaming the car thinks the temp is fine, and it doesnt do it every time, it has only begun this when it started to get a bit cooler. So my dilemma is that I dont know if I should throw a new radiator in there for $500 or put a thermostat first which is much cheaper. The thermostat on this car has been replaced one other time before about 2 years ago, I think it was boiling out of the bucket though when that went.

What do you guys think? Thanks for your replies.

 

[greasemonkey524]

Well if you said you saw it coming from the radiator cap I would try that first. It may not be able to hold the pressure anymore. I think they're supposed to be able to hold 16lbs but I'm not entirely sure. The cap would be your cheapest route to start with.

 

[JCell]

a bad radiator cap will definitly make you overheat

cheap mod that works, after that try the thermostat, also a cheap alternative

if both still fail...

 

[major error]

(iagree)
start with the cheap/easy fixes, then work from there.
Another distant possibility is the water pump, but they're designed to leak before failing... but when they fail, the car overheats.

 

[Divinehammer]

I asked all the places about a radiator cap and they said probably not. Now when the car steams it has never once overheated (according to the gauge) even when it is in full steam gauge reads halfway up no fluctuation or shaking of the needle.
so do you still think that a new radiator cap could be causing the coolant to start steaming out.

Thanks for your replies.

 

[major error]

A couple other things I thought of:
When was the last time the system was flushed/cleaned?
When the car is at normal operating temperature, do the vents blow hot or only sorta warm?

Personally, I'd still do the cap & thermostat, just for piece of mind and to rule out all the possibilities.

 

[Divinehammer]

A couple other things I thought of:
When was the last time the system was flushed/cleaned?
When the car is at normal operating temperature, do the vents blow hot or only sorta warm?

Personally, I'd still do the cap & thermostat, just for piece of mind and to rule out all the possibilities.

Do you mean can I run the heater at fully hot temperature? I think that it does I will have to check. It has not been flushed or cleaned for probably 40k miles I think when I wanted them to do that they couldnt do the flush just drain all and refill. I did ask the Mazdatech if a flush could possibly be a remedy and he said no.Thanks.

 

[major error]

Do you mean can I run the heater at fully hot temperature? I think that it does I will have to check.

yes. That's a sure sign that the thermostat is opening. As for proper function? AFAIK, if it takes forever to heat up, that's a sign that it's stuck open; no/little heat is a sign of stuck (partially) closed. my non-educated .02

It has not been flushed or cleaned for probably 40k miles I think when I wanted them to do that they couldn't do the flush just drain all and refill. I did ask the Mazda tech if a flush could possibly be a remedy and he said no.

I may be wrong, but isn't a flush supposed to be a maintenance item every other year?

Thanks.

just trying to cover all the bases...

 

[major error]

Actually, now that I think about it, where is the water pump on the Protege?

I had one fail on my old Ranger @ ~165k. I never saw any steam, puddles or any leaking, but a week or two before it died (and the car overheated), I had refilled the reservoir a couple times.
Like I said, water pumps are designed with weep holes that start dripping before a complete failure. It's entirely possible that the coolant is splashing from there...

 

[Divinehammer]

Actually, now that I think about it, where is the water pump on the Protege?

I had one fail on my old Ranger @ ~165k. I never saw any steam, puddles or any leaking, but a week or two before it died (and the car overheated), I had refilled the reservoir a couple times.
Like I said, water pumps are designed with weep holes that start dripping before a complete failure. It's entirely possible that the coolant is splashing from there...

I dont think that it is the water pump because the majority of the coolant is on the bottom of the radiator I could see the trails the residue left running down the plastic pan on the bottom seemeing to come from the crease/crimp but it could have run down from somewhere else and ran along the crease. So all of this coolant is in front of the water pump I think. I was looking at the radiator caps from corksport and thinking one of the high pressure ones might be good. They are better than the Stock ones right. But my thing is if the cap is my weak link wouldnt I be having problems more often than I am.

 

[Speed3.5]

well i've noticed coolant fluid to go down lately more often than i imagined. I've driven the car for more then 1.5 years w/o a drop of coolant fluid (at that time i had TT working, now i took it off for some reason). I changed my radiator cap and it seemed fine but every other week i see the fluid to go down by ~.5cm which worries me too. My Temp gauge shows normal the whole time and i try to cool off the car when i can (rare) , could be the turbo burning the fluid as it's used to cool it off, engine oil doesn't change its level from the oil change either.