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Overheated? I hope not. (plus compression test results)
Well, today was a pretty productive day on the car...until the end of it. I drove it about 90 miles in total, went and grabbed a replacement coolant temperature sender so the gauge cluster temp gauge would work again, installed that, gauge works perfectly. I changed the plugs out for brand new NGK 7's and 9's. Performed a compression test while I was at it.
With the engine warm, and normalized altitude & 250 cranking RPM, the front rotor scored 117, 115, 113, and the rear rotor 111, 113, and 112. I reinstalled the new plugs and took the car to get groceries. As I was pulling into my driveway, I noticed the OEM temp gauge on H. the AEM water temp gauge was reading about 184 or so. As I stopped in the driveway I turned it off, and the temps on the AEM gauge climbed to 240, and then started to steadily come down. The OEM gauge remained near H for the most part, but the AEM reading dropped all the way down to about 184 before i turned the fans off. The AEM temp sensor is mounted to the front of the housing the filler cap is on, for reference.
I looked under the car, directly under the coolant overflow container there was about half a cups worth of foamy coolant puked on the ground. I felt the lower radiator hose that comes out of the engine by the crank pulley, that hose was warm. I felt the top hose by the filler cap, it was barely warm at all, in fact I squeezed the hose and it felt like it didn't have anything in it. The AST wasn't warm either. (for the record the car never smokes at startup or anything of the sort.) I didn't see any coolant present anywhere else, nothing leaking from the waterpump, etc. Though there was a very tiny amount of bubbling coming from where the black piece the fill cap screws onto bolts onto the thermostat housing.
The previous owner replaced the thermostat with an Atkins one probably a month ago, and I didn't seem to see anything out of the ordinary with the waterpump..can anyone chime in with some advice? I don't understand why the two temp gauges would be showing dramatically different readings as well at one point.
Can someone help me make sense of this?
Edit: I have noticed since I bought the car it does sound like it has a supercharger when I drive it (think the cybernetic whine noise) Possibly the bearings on the waterpump?
Also, worth mentioning, The cap on the filler neck looks like the normal radiator cap, I believe the cap on the AST doesn't have a spring, its like a generic cap. Could this possibly be contributing? I've read that the cap with the spring needs to be on the AST, not the filler neck.
I also did not hear any water/coolant boiling during this.
Just want to note the reading from the ecu and the dash can be different. The reading from the dash is from a sensor in the rear iron. The ecu reading is from a sensor behind the thermostat.
A pinched radiator hose that feeds the water pump could give the results you are experiencing. Possible overheating, which the rear iron sensor is capturing but a ecu temp that appears to be in range.
Just want to note the reading from the ecu and the dash can be different. The reading from the dash is from a sensor in the rear iron. The ecu reading is from a sensor behind the thermostat.
A pinched radiator hose that feeds the water pump could give the results you are experiencing. Possible overheating, which the rear iron sensor is capturing but a ecu temp that appears to be in range.
I don't think any hoses are pinched, though. It just happened pulling into my driveway. The AEM gauge sender is located on the front of the filler neck, and the factory temp sender for the factory gauge like you mentioned is located above the oil pressure sender. That one read on H, but the AEM one was reading 240 then quickly dropped down to 180 in a matter of about 30-60 seconds. It wasn't at 240 for very long. No boiling, so Idk whats going on..
this whole time i'd been driving it with the caps the way they are, I don't know why whatever it was decided to show itself now, I'm going to try swapping out the caps for new ones. Anyone have any idea which ones to source at Advance? All they have is the 16 PSI.
Should I just go in and say I need a 13 PSI cap and a zero PSI cap? Also, idk if the cybernetic whine I hear while the car is idling/driving is the water pump bearings or not, but its not leaking
First off, this is why I always recommend putting your aftermarket water temp gauge in the coolant line in the back of the block. You want to see the temps the engine sees, not the temps at the thermostat housing. Most likely you have a sticking thermostat from what you are describing.
I would start with a new Mazda OEM thermostat from Mazda. Atkins has a lot of parts that they source from aftermarket or make themselves (gaskets) - some are good, some are not. I've seen MANY times where aftermarket thermostats stick or stay closed in a very short amount of time - like a month or so.
Hopefully your coolant seals are fine, an overheat situation doesn't mean instant seal failure. A lot of if depends on the health and age of the engine, as well as what temps it normally runs at.
Anyhow, go get a Mazda OEM thermostat and look into moving the temp sender for your AEM gauge. Here is my thread on the topic, it's easy to do with parts from Home Depot and it's dead reliable -
First off, this is why I always recommend putting your aftermarket water temp gauge in the coolant line in the back of the block. You want to see the temps the engine sees, not the temps at the thermostat housing. Most likely you have a sticking thermostat from what you are describing.
I would start with a new Mazda OEM thermostat from Mazda. Atkins has a lot of parts that they source from aftermarket or make themselves (gaskets) - some are good, some are not. I've seen MANY times where aftermarket thermostats stick or stay closed in a very short amount of time - like a month or so.
Hopefully your coolant seals are fine, an overheat situation doesn't mean instant seal failure. A lot of if depends on the health and age of the engine, as well as what temps it normally runs at.
Anyhow, go get a Mazda OEM thermostat and look into moving the temp sender for your AEM gauge. Here is my thread on the topic, it's easy to do with parts from Home Depot and it's dead reliable -
Well, this would be about a month, the previous owner installed it prior to me purchasing it. Would that explain the coolant being puked out of the overflow as well? I'll see about relocating the AEM gauge sender, I did find it odd that it was located post thermostat.
It's normal for the coolant temps to jump after shut down. And, the stock temperature gauge is not linear. There are plenty of threads about the stock temperature gauge being unhelpful. So, your AEM gauge is the one to pay attention to. You can linearize the stock gauge, or use a PFC to get workable temp data from the stock sensor.
Try to let the car idle for a few minutes after a hard/hot drive, to let the fans bring the overall system temp down. You can turn the AC on low and turn the parking lights on to get the cooling fans to come on medium while you idle. 240 is too high, and those tips ought to help keep it more normal. It sounds like you boiled after shut down and puked some coolant.
Definitely check the belts and belt tension. And you can get the stock AST and filler neck caps from atkins. The AST should have a pressure cap, and the filler neck just has a hard cap. You could find non-OEM replacement types if you cared to in the same pressure and cap type.
Well, this would be about a month, the previous owner installed it prior to me purchasing it. Would that explain the coolant being puked out of the overflow as well? I'll see about relocating the AEM gauge sender, I did find it odd that it was located post thermostat.
When the car does overheat, it can and will shove coolant into the overflow tank that can be boiling. The boiling tank can "boil over" onto the ground, there's a hole at the top of the tank that the coolant will come out of.
Well, this would be about a month, the previous owner installed it prior to me purchasing it. Would that explain the coolant being puked out of the overflow as well? I'll see about relocating the AEM gauge sender, I did find it odd that it was located post thermostat.
There's nothing inherently wrong with a water temp sensor in the thermostat housing, or post-thermostat. Mostly a matter of quirks and preference.
Well, I went ahead and replaced the pressure cap on the AST as well as the thermostat. Mazda didn't have one available until next week, and I couldn't wait until then, so I purchased a carquest brand, and tapped the bleeder hole myself. Made sure to align it to the 12' position. Fun fact: I wanted the 13 PSI cap, not the original higher pressure one that was originally on 93's that was recalled. Easy way to find the right one is to just look for a 94-95 radiator cap in the system at autoparts stores. Those default to the 13 PSI, not the higher rating you will find if you search for a 93.
People probably know that already, but I just figured I'd throw it out there in case.
Car was down an entire jug of coolant, so it must have been continuously burping it out since I've been driving it. Filled it up, started it, let it run, it did have one point where it shot to around 230, but promptly jumped back down, so I think there is still air in the system. With the AC fan on and just idling, temps hover around 184-186. Without, I think it would be around the 200 range.
Mostly clear
Now you have to bleed the coolant system. Should be a thread in the FAQ about that or search for one.
Dale probably posted or started a thread on the topic at some point over the last decade
Originally Posted by Narfle
There's nothing inherently wrong with a water temp sensor in the thermostat housing, or post-thermostat. Mostly a matter of quirks and preference.
Personally, I think that is the dumbest place to put it.
The location Dale mentioned ensures you are getting temps at the hottest point of the cooling system (so you have good data on max temps your engine is running) and it always sees a reading.
Personally, I think that is the dumbest place to put it.
The location Dale mentioned ensures you are getting temps at the hottest point of the cooling system (so you have good data on max temps your engine is running) and it always sees a reading.
That's fine. I've never seen any data to conclude that theres a wide variance between the two location, except on warmup before the thermostat opens. The water temperature measured at the hot side of the radiator (ie: the thermostat outlet) ought to be plenty indicative of overall cooling system performance. Mazda put the temperature switch for the fan on just the other side of the thermostat. There's plenty of corollary to know it works fine and is probably a moot argument.
So the car has been idling high since I bought it, The entire time today it has sat at 1600 rpm. Sometimes it will "hunt", but not very often. It will do the 3k god awful AWS when cold that I blip the throttle to cut off.
So I'm wondering if I should start with the TPS or adjusting the idle on the TB. Turning the ac on/off doesn't induce a bump of the idle, but probably because it is so high already?
Car is currently (and unfortunately) an Auto, but that will be changing. However, in the meantime, I'm trying to get this idle under control.
Is it an auto? You can start manual cars in-gear to avert AWS.
Sounds like you may have a vacuum leak, if it's hunting and idling high. Try backing down the main throttle adjustment. Check for obvious vacuum leaks, a smoke tester and the FSM diagrams will help. Maybe it's where you disturbed things removing them.
If it's not those things, then get ready to try the TPS or do the vacuum hose job.
Is it an auto? You can start manual cars in-gear to avert AWS.
Sounds like you may have a vacuum leak, if it's hunting and idling high. Try backing down the main throttle adjustment. Check for obvious vacuum leaks, a smoke tester and the FSM diagrams will help. Maybe it's where you disturbed things removing them.
If it's not those things, then get ready to try the TPS or do the vacuum hose job.
I don't believe I've touched anything aside from removing the crossover pipe to do the thermostat. Which, I'm pretty sure those couplers are tight. What line would you use for smoke testing (just going to get a cigar, lol)
It wouldn't be the crossover pipe. Cigar could work. Did you move the pressure tank to remove the crossover pipe? Have you done any other work? Have you burped the coolant well?
It wouldn't be the crossover pipe. Cigar could work. Did you move the pressure tank to remove the crossover pipe? Have you done any other work? Have you burped the coolant well?
By pressure tank do you mean the black box foreward of the UIM with two visible vacuum lines coming out of the right side? That's snug and secure, nothing wrong with it, It was moved slightly, but not anything more than an inch or two, I didn't see any vacc lines disconnected from it, or hear any audible *hissing.*
So the car has been idling high since I bought it, The entire time today it has sat at 1600 rpm. Sometimes it will "hunt", but not very often. It will do the 3k god awful AWS when cold that I blip the throttle to cut off.
So I'm wondering if I should start with the TPS or adjusting the idle on the TB. Turning the ac on/off doesn't induce a bump of the idle, but probably because it is so high already?
Car is currently (and unfortunately) an Auto, but that will be changing. However, in the meantime, I'm trying to get this idle under control.
Always adjust the mechanical settings on the TB first. Make sure those are accurately setup. Then the TPS can better do it's job.
Well, filled the car up with coolant again, tried filling up the overflow, it started pouring down the sides of the overflow tank, so I figured the overflow must have been full. topped off the coolant, it didn't take much. Let it run. Temps held around 186-192 with the ac fan on. I noticed the coolant reservoir having a steady slow stream of coolant falling onto the ground.
Opened the cap, let the car run, and I see this:
I really hope this is not a blown coolant seal, but it looks like it. Revving the engine or holding the idle up will eventually result in it puking coolant out the filler neck.
Liquids (i.e. water and coolant) expand as they get hot. If the overflow / reservoir thing was full or close to being full cold, then I would totally expect it to overflow as the coolant warms up and expands.
If you remove the cap at the thermostat (your pic) and rev the car, it's normal for it to overflow at that location. You are also adding air to the system in doing so - which means you should bleed it again. Fun times, eh.
It usually takes me a few cycles of running the car, letting it cool, refilling to get all the air out. Even with the Lisle funnel. YMMV there.
I also Suggest you go to the local auto parts store and rent a cooling system pressure tester aka radiator pressure tester and use it to check for leaks. That will also help you to diagnose if you have a bad coolant seal.
Coolant seal failure is very easy to misdiagnose so don't get dejected yet.
Liquids (i.e. water and coolant) expand as they get hot. If the overflow / reservoir thing was full or close to being full cold, then I would totally expect it to overflow as the coolant warms up and expands.
If you remove the cap at the thermostat (your pic) and rev the car, it's normal for it to overflow at that location. You are also adding air to the system in doing so - which means you should bleed it again. Fun times, eh.
It usually takes me a few cycles of running the car, letting it cool, refilling to get all the air out. Even with the Lisle funnel. YMMV there.
I also Suggest you go to the local auto parts store and rent a cooling system pressure tester aka radiator pressure tester and use it to check for leaks. That will also help you to diagnose if you have a bad coolant seal.
Coolant seal failure is very easy to misdiagnose so don't get dejected yet.
Coolant was coming out of the overflow at a decent drip rate for a solid ten minutes. Of course it was full when it was cold, because I tried to add some and it started leaking. But should it really barf that much coolant into the overflow that it would still be dripping for a combined 30 minutes approx that the engine was running? The car never overheated, sitting on a hot day idling the whole time it never got above 196 with the ac fan on.
I'll rent a pressure tester and see. I really hope its not a coolant seal. Car doesn't smoke in the tiniest bit, but I know that's not a deciding factor.
+1 on the above. You should get a lisle funnel, warm up and shut down the car a few times. I'd flush n burp the coolant real good, before I blamed the coolant seals.
08-25-19, 06:27 PM
