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Enginge temp OK, no heat at all

15K views 42 replies 12 participants last post by  dillymanilli 
#1 ·
It's been getting pretty cold and usually I don't have to drive my car much, as I can walk to school. Unfortunately, I got in my 2002 325i last night and while driving I noticed the engine temperature needle was dead center, meanwhile the air blowing from my car was extremely cold. I had the heat set to 91F and it was still blowing, what felt like, AC air.

I have read thermostat failure is usually an issue when the engine temp isn't getting to where it should be, but this didn't seem like the case and I'd like to self-repair this when I get back to my hometown and have access to tools + a garage :D
 
#17 ·
why would you make blanket statements like this without even knowing what has been done to the car. For all you know it might have new cooling system on it and just needs bleed out.

This is just the reason I avoid this website due to people like you that think they know everything without all the facts.

It's just like telling someone to replace the engine becasue the oil light came on.

You need to dignose the car correctly before just throwing money at it.
 
#4 ·
Low coolant could be the first concern. Check the sensor in the lower radiator hose, if it is wet at all around the switch or on the lower engine cover the O-ring for the lower radiator outlet temp sensor is leaking.

Air in the system is the next issue, but this kind of goes along with low coolant.

Center dash vent not on the 3 red dots.

Then read the 3rd link below in my signature. Note that the temp gauge is buffered and it is not accurate at all.

Be very careful if you top off the coolant level. BMW states the coolant should be checked at 68F. If you top off the coolant when cold, set it to the minimum level otherwise you will be back here in a few days with a split expansion tank.
 
#6 · (Edited)
#7 ·
^I'm with dslboomer. The heater control valve is a part that is known to give out on occasion. I just had a similar problem but the reverse (no cold air, thankfully summer was over haha). I just bought a cheap valve off of someone who was parting out, threw it in and vualah. Check your valve out and see what type of condition it is in.
 
#10 · (Edited)
Here, you prove it again that you don't have any diagnostic knowledge or skill.
Let me say it again: you are a mere part changer.

If there is air pocket in the system, first symptom will be overheat.
If coolant is low, there will be warning provided his/her coolant level sensor is working.

No amount of new cooling parts will fix the no heat problem in the cabin if the heater valve is bad.

Which is the right order for diagnostic and repair?
1. Spend about $1,000 on cooling system parts and a couple of days of work, but find the heater valve is defective.
2. Spend a couple of hours inspecting the heater valve, but it is working ok. So, go to the next possible cause.
 
#9 ·
I find more heater problems due to low coolant and air pockets than anything else.

Not sure how you plan on checking or determining if the heater control valve is a problem until you verify the engine coolant level, engine coolant temps and check for air in the system and purge air if there is any.

Then after all of that first round basic troubleshooting, then the OP can come back and say everything it fine, then you move on to things like heater control valves, water pumps that are broken/cracked/spinning or determine if there is a hose or connection that is blocked. Have not seen a lot of blocked passages on these cars, but have seen it on plenty of others. But if the cooling system has not been reasonably maintained in this car, green coolant or something else all bets are off.

Still plenty of other possible problems, but with anything, rule out the basics first.
 
#15 ·
It's been getting pretty cold and usually I don't have to drive my car much, as I can walk to school. Unfortunately, I got in my 2002 325i last night and while driving I noticed the engine temperature needle was dead center, meanwhile the air blowing from my car was extremely cold. I had the heat set to 91F and it was still blowing, what felt like, AC air.
What does the outside air temperature read on the dash?
If it shows 120F the Heat/AC system may just try to pull in what it thinks is hot outside air to warm the car. The sensor is located on the bottom drivers side in front of the front wheel and many times is ripped off by road debris. Search for a thread titled Ambient Temperature sensor or something like that for more info.
 
#16 ·
I would check my system for leaks first. This would involve getting under the car, up on jackstands, and seeing what's going on. Looking for coolant drips, residue etc. Remove the undertray and see for yourself. You will probably find coolant underneath the expansion tank area. If you do not want to go mango/buckshot method, then you'll need to inspect your system for leaks. Assuming you find one, replace appropriate parts and rebleed system.
If no leak is found, I'd then move to checking the heater control valve. My money is on a leak which has led to an air - bound heater core. Definitely happened to me too. My expansion tank had the smallest of cracks down the side of it and was very hard to diagnose, which is why I say look for signs of coolant first.
 
#21 ·
It sounds like the e46 cooling system is very sensitive. One small leak will mess up alot of shit. Im having an issue of not having any heat inside the car and im pretty sure theres an airlock in the system. Is bleeding the system pointless if theres air finding its way back in? Thats what I think is happening to me but cant pinpoint the exact location. Also when you see coolant coming out of bleeder screw you tighten it then you need to take some coolant out of the expansion tank
To bring it up to level?
Sent from my GT-I9100M using BimmerApp mobile app
 
#22 ·
Just an update. I had no heat coming through the vents. The only time i would get any kind of heat is if i bled the system. I would drive around with good heat then it would start blowing cold and continue blowing cold.

Today i replaced everything in the cooling system. No leaks. I even tested the heater control valve. Looks good there. I ran compressed air through the heater core. Got flow through heater core. I bled the system. After all that monkeying around i stilll had the same issues. Blew hot air for the first little bit the nothing but cold air. I dont know what else it could be. Im seriously lost here.

I think theres an electrical problem here or theres still air in the effing system. If the problem is electrical what should i look for. People say to blow the grill next to hvac control unit but what woould that do? Any input would be great. The weather here drops to -30 celcius. I cant have this continue.
 
#24 ·
Only place I know that can suck air is at the temperature sensor on lower radiator hose. Have you changed the o-ring there?

To be sure, you may rent a cooling system pressure tester and check for pressure drop, leaking coolant, and air bubble by spraying soapy liquid around the suspected areas. It may not have a right adapter for E46 though.
Asking dealer or shop to do just pressure test is an option.

 
#27 ·
Yes I did put in a new t stat. The funny thing is, is that the car does produce heat but only for a few blocks. I think the system has air in it but is not coming out with the cold engine bleed procedure. I'll give it another go tomorrow. Will post back.

Sent from my GT-I9100M using BimmerApp mobile app
 
#33 ·
I bled the system real good this morning. Brought the car up to temperature and still no heat. I looked under the hood while the car was running and it might be just me but the pulley attached to the water pump looks a little wobbly.

The old water pump, i forgot to add had a definite wobble to it. Would loose tension in the drive belts cause the water pump not to pump efficiently allowing it to go through heater core?

Also both hoses going to heater control valve are hot but the hose that exits the heater core to the expansion tank is relatively cool. What does the mean?
 
#34 ·
Wow feel like im talking to myself here lol. So i think im onto something with this no heat issue. Bled system again and had the car idle till it hit 96 celcius. Good operating temperature. Started having great heat. The heat only lasted 10 min or so as usual and then gradually got cooler. Hoses to and from water valve were hot. Hose from heater core to expansion tank was hot too but only when i was getting heat through the vents. As the vents started blowing cooler air, that hose from the heater core to the expansion tank started to lose heat and go cooler too. As i was moving that hose around i noticed dripping from the fitting from hose to exp tank. Small leak? Air getting into that hose? Im gonna replace it and see if that helps? What are your thoughts?
 
#36 · (Edited)
You maybe onto something there.

Don't feel bad!
You are actually doing good by experimenting and documenting your work, so everybody can learn and help each other.
Probably 95% of Qs in this forum are not followed up.
 
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