Overheating...again

Sitting in the driveway listening to a song on radio this evening I see the temp needle start to creep up. This is the 2nd time it's done this since I've been driving it again. It spent 5 months in the driveway this fall while I drove the other car (strange circumstances, car was running fine).

Popped the hood and the fan was blowing but it seemed a little weak. Hit the AC button and when it engaged the temp actually went down. Assuming it was because of the extra fan running I got out and checked, the AC fan was blowing at least 200-300% stronger than the drivers side fan.

I am assuming that both fans should be moving the same amount of air and this is not normal?? Are the bearings going out in that fan? I have a spare set of fans in the garage if that's the case but wanted to make sure before I started tearing things apart.

The coolant was a little low when I started driving it again but I topped it off a month ago. It's been over a year since I flushed the coolant and probably needs it, should I run some radiator flush through it while im at it? That being the case it still shouldn't be overheating sitting 5 minutes on a rainy afternoon in March with the AC off. The temps afe fine on the road so it's drivable now, hopefully I can fix it while it's still cool...there's no way I would make it through summer like this.

So you are selling the car because the fan is bad? (you accidentally posted in the classifieds ;))

oops...how did this end up in the classifieds...

Can somebody move it to Tech?

...Juano beat me to it...

Replace the bad fan.

Replace the fan and run them in parallel. I'm not a fan of any of the coolant flushes. I would just say drain it and run a more TX friendly blend (only distilled water).

Chris

Quote:

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Originally Posted by Miatamaniac92

Replace the fan and run them in parallel. I'm not a fan of any of the coolant flushes. I would just say drain it and run a more TX friendly blend (only distilled water).

Chris

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+1

Replace the bad fan and you should be fine. If they're coming on when they should (one with temp and one with the A/C), then you won't have a problem. Mine run like this and I've never had a problem overheating - even in the most brutal Texas conditions... knock on wood. :rolleyes:

I would go with an OEM fan instead of an aftermarket VatoZone replacement. My prior experience with the latter leads me to believe that those suck and will burn out quicker. Just my $0.02.

I have spare OEM set in the garage from my last radiator blowout fiasco... Never tested them though. I'll swap the bad one and if it's not strong enough i'll go OEM. I don't want to risk anything given my luck with cooling systems...

The fan's aren't the same and If memory serves me right, the A/C fan is considerably stronger.

Huh...that sucks.

Any idea what else would be my problem? The radiator is only a little over year old and I use distilled water so it couldn't be gunked up this soon. I don't have a front license plate blocking the airway, and it was 50 degrees outside.

Water pump going out maybe? The PO said the timing belt was changed around 80,000 miles and im over 150,000 now, don't know if the water pump was changed with the belt either so it could be very old.

Any way to check?

I know that the summer that I replaced the radiator and flushed coolant and everything, it overheated once while running in a parkinglot for about 15 minutes with the AC on, not too bad but enough to blow a half gallon+ of coolant into the overflow bottle. I just assumed black car, triple digit heat index, no air flow was the culprit, but this seems to be an advanced case of that same event 1.5 years later in less than half the time and at less than half the outside temperature. Something's going out...I just hope it's not expensive.

I could wire both fans up in series and that would cure my problem temporarily, but when the summer arrives I would be kicking myself for it if the fan is indeed still good.

Ignore Duane for now replace the fan first then report back. It is not uncommon for the fans to get weak. Plus ya got the parts in the garage!

I agree with Stupid. Replace the fan and report back.

:punchout:

Ouch, Well kiss my ::Bum:: I missed the post where he said he had fans sitting around. Well hell, if you have a spare, by all means give it a shot.

I'll bet it's a t-stat ;)

Quote:

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Originally Posted by TurboDuane

:punchout:

Ouch, Well kiss my ::Bum:: I missed the post where he said he had fans sitting around. Well hell, if you have a spare, by all means give it a shot.

I'll bet it's a t-stat ;)

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Yea, I was planning on at least testing the other fan first. I can just plug it in without taking the other one out right (with necessary safety precautions of course) to see if it's stronger.

The thermostat isn't that old either, I changed it about 2.5 years ago, how long do they last(O'Riley t-stat). Can they get progressively worse over time? I thought they just stuck open or closed.

When I topped off the coolant last month, the radiator gurgled out coolant intil the engine warmed up, then the level dropped and I was able to pour a half gallon or so in there. I assumed this mean the t-stat was working properly. I am still learning this stuff so honestly I dont know.

Yea, I think i'm going to play with that fan this weekend. Since the AC fan is stronger would it be possible (or a good idea even) to put the other AC fan in there in place of the normal radiator fan? I am sure the plugs are different but I think I could splice it in somehow. Maybe that's a bad idea, just thinking out loud.

Miata's eat t-stats. Check to make sure it's not stuck closed.

Quote:

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Originally Posted by sammm

Miata's eat t-stats. Check to make sure it's not stuck closed.

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Especially aftermarket ones.

Chris

Thermostats fail open these days. It doesn't seem likely that it would overheat only at idle if that were the problem. You seem to be having a lot of trouble with cooling and I wonder if we have identified the cause. I'm all for replacing the fan since you've got one but a compression and timing check may identify an underlying issue.

Quote:

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Originally Posted by creek

Thermostats fail open these days. It doesn't seem likely that it would overheat only at idle if that were the problem. You seem to be having a lot of trouble with cooling and I wonder if we have identified the cause. I'm all for replacing the fan since you've got one but a compression and timing check may identify an underlying issue.

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Titus helped me with the timing awhile back and if I remember correctly we set it to 10, or whatever stock specs are.

If I had a compression issue wouldn't I be able to feel it on acceleration? The engine feels very strong throuought the power band. The only thing is a rough idle has showed up in the last month or so, I figured it's been awhile since ive seafoamed it, might be a carbon buildup.

I'm definitely going to replace all the cheapest stuff first starting with the fan this weekend, but out of curiosity what would I be in for with a compression check, how difficult is that to perform, or is that something I need to take to a shop for??

On white I was having "over heating issues" but really it was'nt. I installed a mechinal gage and all was ok.

Ok, I swapped the fan out and just finished flushing the coolant with 60/40. Fan blows at least 200% stronger, which solves part of my problem. I sat it idling for awhile and it didn't overheat, we'll see how she does after highway driving tomorrow. I might have another problem, the fan blows stronger than the AC fan, I might replace that one when I have some time.

2 questions:

First, I ran it to temp while topping off coolant. I never saw the point where the tstat opens and all the coolant gushes in then engine and you add more coolant. Indication of a stuck tstat? (doesn't seem like the car's acting like a stuck tstat though) I've only seen this happen once or twice, so don't know if it's normal or not. Maybe the engine had water in it, and just started circulating...maybe different circumstances last time I saw this.

Second...as I was letting it warm up a small amount of crud came out with the bubbles. This wouldn't be an indication of....oil in the water would it? It's just the normal crud in the old car cooling system right?
*crosses fingers*

http://img.photobucket.com/albums/v4...i/P1040829.jpg
Pic is the water sitting in the funnel, which is sitting in the radiator opening while the car was running.

Thanks for all the help guys.

Doesn't look like oil to me. Is there a 'slick' on top? Try to pinch some of the crud between your fingers and see if it stains/streaks.

nope no slick, just crud...I was lookign for one. I thoroughly inspected it with a flashlight before putting the cap on. But the water was really damn hot, didn't bother to stick my finger in it. Didn't think about checking it for slippery-ness or streaking anyway, was a good idea, but too late now.

It could have also have been some dust blowing in the wind, but it wasn't very windy so I dunno...

You sure are the radiator is half empty type aren't cha! ;)

Not really, just trying to catch the expensive stuff while im not broke and while the weather is under triple digits.

Sounds like you found your problem, and the antifreeze looks fine, you will always see some gunk. Make sure you use distilled water though, to minimize the buildup of gunk and rust within the system.

Also, if you have a stock type t-stat, you don't get that super sucking rush that drains the radiator once the t-stat opens, as the stock type has a bleader hole that allows the air to pass before the t-stat ever opens, thus it is less dramatic when the t-stat does finally open.

Oh good deal. That would explain all the bubbles.

Yea, I made sure to use distilled water. That's why I was flushing the system, since after it burped a bunch of water out I had to top it off with nasty Euless water a few weeks ago.

The drive in seems to confirm something's going right so i'll call it case closed for now, but keep an eye on it for a few weeks.

It burped a little water out this morning, but that's normal with WOT highway driving after a completely full radiator/overflow reservior, right? Temps were normal afterwards so I assume it was just burping out the overflow.

Thermostat check:

Start the car and put your hand on the upper hose. The temperature of the hose will be Pretty cool at first. When (if) the T-stat opens, there will be a sudden and drastic increase in temperature in the top hose. By grabbing both the upper and the lower hoses just after the car warms up (before it is too hot to touch the upper hose), you can get an idea of your radiator's performance. There should be a noticeable difference in temperature between the two.

Fan Parallel Mod:

There is a tip in the tech section of the pointy board where you bridge the signal wire from the ECU to the two fans. When the car reaches the threshold temperature for the cooling fan to come on, both fans will come on. This is the best way to run fans in parallel, because the second fan will not draw electricity from a circuit designed to power only one fan.

^Good info. I plan to run them in parallel, but I want to make sure I root out and fix the problem first and make sure I can keep decent temps with stock setup before modifying anything. I don't want a major failure this summer.