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No heat after expansion tank replacement

6K views 35 replies 12 participants last post by  farkas330i 
#1 ·
My expansion tank blew out on new years eve. Luckley I was able to make it home before temp got up to the 3/4 mark on temp gauge. Anyway I was planning to replace the cooling system this spring since I am new to this car per mangos thread. Being that it happend right after xmas I was only able to afford replaceing the minimum to get back on the road.
I purchased a new tank and a gallon of bmw antifreeze from the dealer. I replaced tank then filled system with 50/50 mix of antifreeze and distilled water and bled as described in mangos thread. All seemed good at first but now I am only getting heat for a few min after engine warms up then it goes cold. While hot if I remove the tank cap it relieves the pressure and heat is fine until the motor cools off then the same thing happens on the next warm up cycle. The upper and lower hoses are as hard as a bike tire until I open the cap to relieve pressure. The level of the coolant is in the middle of the high low mark when cold. I has been so for the last few warm up cycles. When I take off cap while hot I hear air esacape then if I squesse rad hose the put cap back on I can hear air go back into tank but then if a squese the hose with cap on no air comes back out.

My question is can the tank cap be causing an over pressureizing of the system not allowing the coolant to pass thru heat circuit? or possible bad HCV? Waterpump?

The heat worked fine before the tank let go. It was slow to put heat into the cabin until the engine was up to operating temp but work great after that.

I am a marine service teck with over 20 years exp so I know my way around and engine but not an expert on closed cooling systems as we dont use them often on inland lakes.

I plan to purchase a new cap for the tank in the new few days to see if that fixes the problem but I wanted to see if anyone has seen this before.

Thanks
 
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#3 · (Edited)
I have bled the system 3-4 times with heat all the way up and car not running and each time after the first I really never got anymore bubbles out if it. The first time I jacked up the front of the car about 18" off the ground with the drivers side a little higher than the passenger side. I was able to get almost all of the 2 gal of 50/50 mix in. What gets me is that if I take the cap off after it's warm I have plenty of heat.
 
#4 ·
I have bled the system 3-4 times with heat all the way up and car not running and each time after the first I really never got anymore bubbles out if it. The first time I jacked up the front of the car about 18" off the ground with the drivers side a little higher than the passenger side. I was able to get almost all of the 2 gal of 50/50 mix in. What gets me is that if I take the cap off after it's warm I have plenty of heat.
The car needs to be running.
 
#8 ·
OP: You'll need way more than two gallons to complete the fill and bleed procedure. Two gallons is just to fill it. You'll need at least an extra gallon to force all the air out of the system. Lots of water will be on the floor if you've done the job properly.
 
#10 ·
Definitely didn"t get hot enough to blow head gasket. Barely made it to the 3/4 temp mark. I definitely did not run enough to dump a whole lot on the ground so I will buy another gallon of antifreeze as well as distilled water and pump some more though it. Now that I am at the point I am, how should I continue to bleed it? Warm with car running or cold with motor not running? I would assume with heat all the way up in both situations as well as nose jacked up to help air get to front.

Thanks for all the responses.
 
#11 ·
The only thing that happens with the heat on is the heater valve opens allowing hot coolant into the heater core

You need the car running to allow the water pump to circulate coolant and force air to the bleeder screw and cap.
 
#15 · (Edited)
Since I have apparently bled the system incorrectly should I drain the system from the drain in the ET and start over?

Dmax- I searched through mango's cooling guide for your post about your alternative bleeding method but couldn't find it. Poss I overlooked since there is over 800 posts.

I did notice the difference in the hot and cold level is different from the expansion of the coolant being hot.

Has anyone put a clear hose over the bleed screw hole or thread a barb with hose on it and pumped it back into the ET as to not waste a bunch of fluid on to the ground or into a drain pan? Just a thought I had.
 
#16 ·
With the car cold...fill ET to between min and max. Close ET cap. Don't touch bleeder screw.

Key to pos 2...heater on highest temp, fan on low, 3 red dots on the dial between vents

Then start the car, rev to 3-4K rpms for 20 secs. and turn the car off.

Then open ET...add coolant if needed.

Repeat if needed. Do not overfill...stay below the max level on the dipstick.

This way you push air out, don't heat up the car, and the coolant level will reflect a true level...not the level it takes when it's hot.

You don't need to drain at this point. We're assuming you have an air bubble somewhere in the system that's preventing the flow to the heater core...the revs to 3-4K should take care of that.

HTH
 
#19 · (Edited)
With the car cold...fill ET to between min and max. Close ET cap. Don't touch bleeder screw.

Key to pos 2...heater on highest temp, fan on low, 3 red dots on the dial between vents

Then start the car, rev to 3-4K rpms for 20 secs. and turn the car off.

Then open ET...add coolant if needed.

Repeat if needed. Do not overfill...stay below the max level on the dipstick.

This way you push air out, don't heat up the car, and the coolant level will reflect a true level...not the level it takes when it's hot.

You don't need to drain at this point. We're assuming you have an air bubble somewhere in the system that's preventing the flow to the heater core...the revs to 3-4K should take care of that.



Thanks for the breakdown. I will give that a try and post my results. May be a few days.

No fan clutch. It is a manual. The water pump seems to be working as there is a steady stream of fluid coming into the air chamber of the ET. I believe that is what that means anyway.

Thanks for the replys.
 
#22 ·
Bleed. I think it was impee that has a pretty good bleed method. Fill up with water till it comes out bleed screw with heat on. Put cap on and screw on bleeder screw but don't tighten all the way. Then start the car and Rev it a few times, not too hard though. Turn off and rebleed. After You bleed several times turn on the car with heat on full blast and wait till it gets to operating temp, if heat blows hot your good...if it doesn't rebleed...
 
#24 · (Edited)
E46Mango is correct.

TIS steps do not involve starting the car.
I've just done coolant replacement 2, 3 weeks ago and standard bleeding procedure has worked for me.

You have to open that bleeder screw and keep pouring through the filler neck until air bubbles stop coming out of the bleeder opening.

Not having hot air means you have air trapped in the system.

Also do not overfill seems to be little bit confusing advice.
You have to overfill on the initial fill. When I was pouring coolant back in, the filler neck was full to the rim. At that point I only had about one gallon in but I slowly kept pouring and air bubbles kept coming out of the bleeder screw.
You can massage the lower hose to get that mix sucked back in.

When I was reaching two gallons in, air bubbles stopped coming out.
I then closed everything up, hot air on max and fan on max and took her for a spin - all good.

The next day level was at minimum on a cold engine so I just topped it off a tad. I like to be in the middle with coolant level. No issues since.
 
#25 ·
lucas...the thing is now, that the system was filled and improperly bled from the start, that bubbles could be anywhere...and when you fill according to standard TIS instructions, there's no circulation of coolant.

The alternative method 'blows' out the bubbles where they should collect in the ET.

I don't think he can just pour coolant in now and fix his issue so easily...but maybe I'm wrong. Certainly wouldn't hurt for him to just add coolant and see what he ends up with...but usually the only time you'd fill to the top of filler neck is when you've drained the entire system and are slowly adding coolant...waiting for it to come out the bleeder. Now, I don't think it's that simple...but we'll see! lol
 
#26 ·
Coolant does not need to be circulated, D. Air will get pushed to the top through gravity alone. The system is not airlocked. Also, even if your theory was true, the engine has already been started and driven once. Any "circulation" of coolant has already been initiated. He just needs a proper bleed, that's all. I've done several E36s and E46s per cold bleed procedure with 100% success rate.

And yes, the tank MUST be initially overflowing. This job done properly will be messy.
 
#31 ·
Thanks for the responses. I will try to rebleed system in the next few days and post my results. I have to set up for the Chicago boat show for the next few days so I won't be able to attend to it.

It's buggin the hell out of me to not have it right so I will get to it ASAP.

Thanks again.
 
#32 ·
Last night I bled system again with no heat still. However I found that the bottom of the ET cap has started to come apart. The bottom of the cap has deteriorated up to the first o-ring. I purchased a new cap and have it installed. I wish they had one i. Stock when i got tank and maybe I wouldn't be going though all this.
I am thinking that those pieces have gotten lodged in the heater core. My next question is what is the direction of flow from the ET? I would assume that the heater pulls from the bottom if the ET then returns to the middle/ upper hose that goes into the back side of the tank. I want to try to back flush the heater but I want to make sure I don't push the pieces deeper into the core.

Thanks again for all the comments and advise.
 
#34 ·
I wouldn't worry about pieces leaving the ET and lodging in the system too much. I remember when I cut mine apart, someone was worried about their broken ET dipstick getting sucked into the system...and I recall looking at the pieces I had to see if that was possible...and I recall clearly that I didn't think it was. The ET has a number of chambers...and nothing big allowing a piece of cap to leave it. I'd say I'm 97% confident.
 
#35 · (Edited)
Fixed! Finally!!!
I tried the mango method and the dmax method with no heat still so I took all the cooling system parts back off the engine and drained all the coolant back out. I used compressed air to back flush the heater core and hoses and didnt really see anything come out that would stop flow. Then I removed the water valve and cleaned it and check to see if it was working properly by applying 12v to it. Seemed to work fine. I was puzzled not finding anything obvious. I then reassembled the cooling system and bled the system per mangos instructions. With the exception of I put a 6" piece of clear 5/8" ID hose coming straight up off the bleed screw hole. I didn't like the idea of pouring new coolant all over the floor. Filled the ET to the top and started squeezing the lower hose to try to help force air bubbles the bleed screw. The hose really minimized the coolant being dump onto the floor as well as giving me a site tube to watch bubble escape the system. After 20-30 min of squeezing the hose and topping off ET no more bubbles were coming out of bleed screw. I then put 2 90 deg elbows together with clear hose on both ends going from the bleed screw then pouring into the ET cap I the started the car and lightly revved up the engine and I could see a whole bunch more bubbles come out the bleeder. I let run for 2-3 min the shut off engine. I put the screw back in and the cap back on the ET and restarted engine and let come up to OT and the heat was pouring out of the vents better than in ever has before. I will check level of coolant in the morning and adjust as needed.

Wanted to say thanks again for all the advise to get this problem resolved.

Tried to add pic to post but apparently I'm not smart enough to know how.
 
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