Ok guys, I need some help. I was having an overheating issue a while go that I thought had been solved with a bigger radiator. Things have been going fine, what I uaually hit a bit of traffic on my way home in the afternoons, and usually what I will do is turn the AC on and the fans on setting 1. As this turns the fans on, it had seemed to keep the water temps good between 180-190F. But something I've been noticing is that when I turn my ac on, my oil temps will rise slowly, and once the oil temps start to go above 195 or so, the water temps begin to rise past 190 as well (I guess this makes sense since the oil is heating up the engine and thus the engine heating up the water). So I was stuck in traffic today for about 20 minutes an as soon as I hit the traffic I turned the AC on (oil temps at this time was about 180F), but by the time I hit 20 minutes in almost dead still traffic, the oil temps were at 230+ and the water temps were 220 (I'm assuming this was again because of the oil heating up the engine). Now after I got out of the traffic I was on a downhill slope going about 40mph, so I clutched in, kept the fans and ac off, and within about 1 and a half minutes of the downhill coasting the oil temps dropped to 180F and my water temp dropped to about 190. I've also noticed that when I'm driving without the AC on, my ruising oil temp is 150F, but with the AC on, the cruising temp is 170-180F. I used 10W-30 dino oil in my car, change my oil religiously every 1500 miles and my oil filter every 3000 miles. I have no idea what the hell is wrong here, anyone have any guesses. I know the fans work cause I can hear them and feel the vibration of the fans through the steering wheel when at idle, can't tell if they're on when I'm moving though. Anyone have any ideas what is wrong. One thing I was thinking about is the main cat might be partially clogged (I'm pretty sure it's the original cat, and the car has 95000 mils on it). I just don't get what the hell may be wonrg. Anyone have any guesses??

 

I am no expert but i had my radiator flushed and my Tstat changed on my last fd,and that helped my temps.My car seemed to start running hotter when i changed the stock pully to a greddy. You might look into redline water wetter.

 

hmm, maybe the t-stat might be a starting point. I flushed the rad about 3 months ago though, and check the rad level every other day, it's been pretty consistent though. I'm trying to stay away from the water wetter though, heard the material content in them tend to slowly eat collant seals.

 

replace the radiator cap as well. the springs can fail slowly and change the pressure, thus changing your boiling point. it's a cheap fix and something most people don't think to do every time you change your coolant.

 

220 is not over heating.

 

ok, will try that as well. will stop by the mazda dealership tomorrow mornin and pick some up (if they have it in stock, if not, will have to order).

 

well, I wasn't as concerned about the water as I was with the oil, I'm startin to think the reason the water temps got as high as they were was because of the oil, but am not sure (I'm definately no expert, so not gonna pretend to be). THe oil temps got to almost 240F, which I'm thinkin is crazy for sittin at idle for only 20 minutes with the fans runnin.

 

220 is pretty damn close to overheating

 

i dont think its the t-stat..cause if it was, maybe stuck closed, you will experiencing overheating problems wayy early in your ride..especially now in the summer..

you are on the stock rad correct?

 

Close enough for a rotary anyway. I know that would scare the **** out of me (and my coolant o-rings, lol)

 

nope, that's the strange part, I'm running a pretty big koyo (literally twice the thickness of the stock rad).

 

what about coolant mixture?

 

runnin about 60/40 water/coolant

 

When sitting in traffic or just creeping along, air is not flowing strongly through either the radiator or the oil cooler. We all know how hot the underhood temperatures get and without the help of fresh air the under hood temps rise and the natural ability of the aluminum housings to disipate heat becomes less, so the oil and water absorb the excess heat. The reason the fans kick on is because once the a/c compressor is activated there will be more heat generated by the motor to overcome the strain created by the a/c system.

 

but is the heat generated by running hte AC significant enough to make the cooling effect of the fans negligible??

 

yeah, I learnt of the underood temps first hand today. when I finally parkedthe car, I went to open the hood while running the fans with the car off, and I honestly think if the hood had been another 20F it would have burned the skin on my hands. never thought just a hood could get that hot without being on fire.

 

wow, something is def wrong there

even today when i went to work, it was 90 degrees out and i never saw above 185 in water temps..then when i parked the car at work, i dont pop the hood to cool the engine like i do at home, i just let it sit and the heatsoak only got to about 205 max..i have a stock rad and a fmic..

 

yeah, tell me about it, I just don't get it, it doesn't make any sense to me. all of the mods I have on my car:

stock turbos at 10psi
stock motor
downpipe (about 5 months old)
catback (about 3 months old)
koyo radiator (about 3 months old)
new radiator hoses (about 5 months old)
water/oil/boost gauges (about 5 months old)

Since the car does appear to cool down rather effectively after I start moving again, I just don't get what the issue is with the car. Just seems to go crazy when at idle.......... The car runs and acts well. I have a stumble that appears to happen only when the ac is on though (if I'm at 3k or above rpm, when I clutch in to shift, if I'm granny shifting, the rpms will drop to pretty much 500 rpm (the car will seem to want to stumble and cut out for a half second, and then level out). when the ac is off this doesn't happen though, with the ac off the rpm will drop to about 1000rpm and then slowly drop down to about 750-800 rpm. the car's always done this though.

have no idea what the hell is wrong................

 

My stock car does the same with the A/C on (sometimes stalls!) but I don't have any cooling issues so I doubt their related issues.

Don't assume that the increasing oil temp is driving your water temp - it could easily be vice versa.

I'm stumped as to what it could be - I can only throw ideas around. What if flow rate of the cooling system was lower than it should be (for whatever reason). Lower mass flow rate of coolant means less efficient cooling. With air flowing, you might not notice the difference, but with minimal air flow (ie: stopped in traffic) maybe you would. If it was caused by a water pump issue, that would explain why the different radiator hasn't solved the issue. Is it possible that a water pumps impellers become degraded over time, reducing the flow rate of the cooling system? Or do water pumps usually just continue working untill BAM they fail totally. What if for some reason your water pump is mechanically sound but you're getting cavitation issues? That would also reduce the pumps effectiveness and flow rate.

Just tryin to throw some ideas around.....

 

How's the water pump? And I just read what he said above.

 

about 90F today when I was driving

 

not really sure about the water pump to be honest with you, not really sure how to even check that to be honest with you....... any suggestions??

 

Sorry I keep editing my post. My questions keep getting asked before I post. Check the water pump though. Also might want to try a heavier oil. I run 20w50 with no problems.

 

damn it happened again. Does the waterpump squeal at all on startup? Check the belt tension.

 

Has this ever been proven? I believe this has only been a myth, never fact.

Sorry about changing the subject somewhat. I am just curious to know.

Mikey