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2001 Mazda Millenia Cooling System question

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here 2001 Mazda Millenia Cooling System question

This topic contains 12 replies, has 2 voices, and was last updated by Avatar Matthew Montalto 5 months, 1 week ago.

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  • #895204
    Avatar
    Matthew Montalto
    Participant

    Hello All…. Once again I find myself in need of some pro advice on matter involving this 2001 Mazda Millenia 2.5L. This time the matter is the cooling system.

    For starters, this cooling system is not very familiar to me as it has a pressurized coolant reservoir instead of a regular cap on the radiator. Because of this, I have found it impossible to find any good advice on the internet on how to properly bleed the air out of this system.

    Initially I had any issue with the heater core, so I disconnected it and flushed it out and reconnected it and while I was doing that I drained the whole system and changed the thermostat (with and OEM thermostat directly from Mazda). I refilled the system and have made a few attempts to get all the air out of the system (burping it by squeezing the hoses and running it with cap off the coolant inlet… which is the one the high side hose connects to… not the reservoir)…. and the car seems to maintain temp when driving… and even when sitting idle in the driveway…. but when I took it on the road this weekend, it was fine while driving … but if I was stopped at a light for too long it would get close to the red….

    The high hoses obviously is hot as well as the bypass hoses, but the lower hose never seems to get above feeling warm….

    Can someone give me some info on the proper way to make sure I have all of the air out of the system? And, from the sound of this issue, does anyone think that the issue could be that the radiator need to be flushed? I know that the radiator is not original and had been changed at some point prior to my owning the car….

    Thank you for any help anyone can offer…. really appreciate it…

    Attached is a picture of this engine (in the picture the yellow funnel is in the coolant inlet (as Mazda calls it)…. I was running the engine and watching for all the air bubbles to come out)

    Matt Montalto

Viewing 12 replies - 1 through 12 (of 12 total)
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  • #895248
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    college man
    Moderator

    I take it the funnel is in the radiator fill port? That should be the point of air release. With the car hot and idling the coolant
    fan must cycle. I like to see it come on twice.

    https://www.ericthecarguy.com/faq/what-to-do-when-your-engine-overheats/solving-cooling-system-problems

    #895263
    Avatar
    Matthew Montalto
    Participant

    sorry for the delay in response (I never got notified via email of your reply)….

    …my radiator does not have a port with a cap on it…. Mazda calles the cap on the reservoir the radiator cap (which is a pressure cap) and the other cap Mazda calls the coolant inlet port… this is on the engine right above the water pump and connected to the radiator top hose…..

    I have tried bleeding from both ports and I still have the overheat condition…. my fans come on, but never seem to cycle off…. as I write this I have a feeling that the problem may be that the radiator fan is not cycling to its “high” speed….unfortunately the Mazda service manuel I have has such lousey info on how the system should be operating and how to actually confirm its turing up to high when its supposed to,…. thank you for getting back though… really appreciate it

    Matt Montalto

    #895266
    Avatar
    college man
    Moderator

    try this method. start around 12 minutes

    #895412
    Avatar
    Matthew Montalto
    Participant

    Thanks so much for getting back to me and that video (sorry for the delayed response… this car is not driven very often, so troubleshooting is difficult)…(and for some reason I never get an email from the forum to tell me you responded….)

    That is probably the only video I have seen with an expansion tank and it leaves me with some questions…. but first… let me fill you in on the circumstances of where I am at now….

    I tested all my electrical stuff and bottom line is the fans seem to be functioning normally… Ran the car in the driveway which has a very slight incline (not sure if thats relevant, but you’ll understand why I mention it in a minute) and it ran fine…. fans came on… no overheat condition occurred.

    Took it out yesterday (I’m in NYC… 35 degree day…) seemingly no problems… drove to my sons school… which includes a good 20 min parkway drive at 55 mph…. then streets with traffic lights…. parked in the lot and waited 5 to 10 min … no overheat occurred…. so I leave to drive home and somewhere along the way I get stuck a light and I notice the temp is climbing past the half way mark (bluetooth scanner says its about 225 or so during this climb…)… once the light goes green… temp drops down without issue…. …and it will run about 218 or so…. [This then happens again at essentially every traffic light all the way home…. about 5 or 6 more times]

    (…when I was stopped in the parking lot earlier it was sitting at 222 but the nieedle stayed at the half way point)

    So I make it home and park on the street (also a slight incline) and open the hood…. figuring I have a couple mintues to check the fans before it overheats again…. – Under the hood I find the fans are working fine… and the car then maintains about 222 degrees and the needle stays at the half (normal location)….. Now at a loss… I close the hood, get back in and put it in drive and wait… and nothing…. no overheat occurs….

    So now I am at a loss… does the fact that i am on a slight incline have any relevance?…..I dont know…. In watching the video you sent, I see there is no need for the funnell…. well when I first bled the system I did so putting the funnel in the top of the expansion tank and when it got hot enough… I came straight up and filled the funnell…. what does this mean? have I now put too much coolant in the system…

    Would love to hear your thoughts and opinion on the matter… as of now…. the plan of action I have is to try again to bleed the system by simply cycling it with the cap off the expansion tank and just use a catch pan and see if it overflows…

    Thanks for any advice you can give me…..

    Sincerely

    Matt Montalto

    #895424
    Avatar
    college man
    Moderator

    Hi Matt,
    The incline is to help the air raise to the highest point to burp or bleed out quicker. It sounds like you are getting there. on your
    system I would not use the Funnel. Just the tank it self. The reason the coolant is coming up out of the funnel is due to air and expansion.
    You could either turn off the car and let it settle back down or put a pan underneath. It can be a messy procedure. Check the coolant level
    After the car has sat over night. There should be a min and max position. Adjust the coolant as necessary. The coolant will also start to expand
    due to no pressure on the system. Pressure controls temperature. Try Eric’s procedure again according to the video. You could also try leaving
    the cap off the expansion tank after you do the procedure for the night. as the car cools it will help with the air escaping if there is any left. Just
    remember to put it back on the next day or before you drive it again. Good luck and keep us posted on your progress.

    #895426
    Avatar
    Matthew Montalto
    Participant

    Thank you again for getting back…. seems to me that you think that the problem could just be that I haven’t gotten all the air out of the system….. and I was thinking that but I feel that its just crazy that its this hard to bleed this system…. but at least that diagnosis make logical sense…. I am going to try what you said… probably tomorrow…. I did get a chance to drive the car last night…. short trip though…. did not overheat… and the heat was working pretty well…..

    Thanks so much for taking the time to help me…. will get back with some followup after I get to try this out hopefully this weekend…. have a good one and thanks again

    Matt Montalto

    (oh, I figured out why I wasnt getting notified to the thread replies….. mail was going my spam folder…. Fixed now… thanks a lot gmail….)

    #895427
    Avatar
    college man
    Moderator

    you got it matt. I think your close to having the air gone. These systems can be a pain in the ass. keep us posted on your progress.

    #895477
    Avatar
    Matthew Montalto
    Participant

    thanks for the advice…. I spent about 40 min with it over the weekend and ran it with the reservoir cap off and watched it cycle…. I kept is at 2500 rpms until she hit about 212 degrees and the fans came on and cooled it to 206 and they went off….. I watched it cycle like this a couple times….. (while this happened the fluid level in the reservoir went down… so it got sucked in… and I checked both hoses (upper and lower) were appropriately hot……so I feel the system is working properly….

    I then cut the throttle back to idle… 600 rpm and up came some coolant and overflowed a little… a good couple of cups worth…. and the temps went up and the fans came on, but it seemed to hold at 222 degrees … not going any hotter…. and as soon as I gave it throttle, the temp would drop back down… and if I held it there (2500) it would go all the way back down to 206 and the fans would go off as expected….. — after this, I then released the throttle back to idle again and more coolant came up and the fans came back on and the temp rose back up to 222 and stayed there.

    I let it sit idle at 222 for a good 5 min and did not see any overheating, so I am hoping that what I did finially solved the problem….. So I did like you said and left they cap off the reservoir overnight to let any more air escape and the next morning I came out and the level of coolant was a little low, so I added enough to fill it to the line marked “low”.

    I drove the car and had no issue, but it was a very short drive so I cannot consider it a completed test as of yet, but I wanted to thank you and run my events and findings by you to see if maybe I am missing something. Thanks again… will report back to (hopefully) say when I have a fully successful test… thanks again.

    Matt Montalto

    #895478
    Avatar
    college man
    Moderator

    Hi matt,

    It sounds like everything is working out. I believe you got. Just check the reservoir one last time when it sat overnight.
    Happy Holidays.

    #895534
    Avatar
    Matthew Montalto
    Participant

    well… I checked the coolant level again after letting it sit and to my surpise the resorvoir was empty…so i filled it and went for a drive…. ultimately it overheated and was not coming down even when moving now… I checked and reservoir was empty again…… filled it again and made it home, but barely…… next day put it in driveway and got her up to temp and now I see the problem….. seems to be leaking when system is under pressure… In all my past tests to bleed the air out, I had the cap off, so the pressure just pushed the coolant into the expansion resorvoir…. but now with the cap on, I can see it is leaking from quite possibly the water pump. either that or the heater core because its on the passenger side… though if it was the heater core I would think I would smell it inside the car.

    So it is likely the water pump…. more likely the gasket has probably gotten cooked in all this running hot…. I put that water pump in myself a couple years ago and haven’t had any issue with it until now ….. I guess the only saving grace is, athough it is behind the timing belt, it is not driven by it so I think I can at least sneak it out of there without having to take the timing belt off and re-do that again….

    once our weather gets out of the 30’s for a day or so I will have to get out there and pull off the timing belt cover and confirm the leak with a pressure tester….. thanks again for all the advice and help

    Matt M

    #895545
    Avatar
    college man
    Moderator

    If the system runs to long cavitating it burns the seal and will start to leak. At least you found the problem.
    15 degrees today here. not a good day to tackle it. Keep us posted on your progress.

    #895547
    Avatar
    Matthew Montalto
    Participant

    yea… weather is brutal here as well…. looking at sunday as a possibliity… …. i have to admit though that I am almost “happy” to find that… at least now there is some logical reason that I was having such difficulty…….. I would rather have to fix a problem then just go on “not knowing and wondering…” ….will keep you posted and thanks again

    MM

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