"The shark"-E21-Overheating issue

[Lebindor]

Hey guys,

I am looking for some help on an overheating issue I am dealing with with my 1981 E21 320i manual.
I am fairly new to working on this engine so sorry for some obvious things that I am asking about.

This is the sequence of events and what I have done so far:

1-Was driving to work which is 20 min ride and I noticed that my temperature gauge was right in the middle. Usually it is a little below the middle which is what I am used to.
2-Same day, the car would start, idle for 4 seconds than shut off. The weather was bad so I got it towed home to diagnose.
3-Checked for vacuum leaks, and tightened everything around. I looked at the muffler and it turned out it was broken or probably blocking the passage.
4-Took the muffler out and the car started. It was loud but it was running.
5-I had also ordered a thermostat and decided to change it while waiting for the muffler to come in from Ansa.
6-Changed the thermostat (after i boiled it and checked that it is opening), flushed the radiator with the hose, changed all hoses, lifted car about 1 foot from the front, to bleed the system from air, added coolant as needed. placed the cap, with heat and fan on high. Hot air was coming in the cabin. Car ran for 15 minutes. Temperature was a bit below the half. I turned the heat on cold, ran for 10 minutes and temperature stayed below half.
7-Received muffler and installed. (3 center pipe bolts were a nightmare to take off lol)
9-Took car for a test ride: 10 minutes of driving between 30 mph and 60 mph and car was overheating. I had to stop multiple times to prevent the temperature to go above 3/4.

What I have done after that:
1-Checked and cleaned ground connection near battery behind the left head light
2-Checked fan clutch but it is not broken
3-Realized the aux fan is not turning on; started the car with the ac aux fan on but still overheated
4-Car overheats on idle now
5-Checked all fuses

Plan next:
1- Waiting for a new radiator cap, temperature switch radiator

Can you please help me with any ideas to try to fix this problem?
-Does adding the muffler have anything to do with that? I do not feel any losses in power
-Any other temperature sensors that should be checked?
-Did i bleed the system correctly? how can i confirm that?
-When the car is at a normal operating temperature, should the hoses (thermostat to engine, engine to radiator) be hot and hose from thermostat to bottom of radiator be cold?
-I read about cleaning electrical connection to gauge, are these behind the instrumental cluster? the black clip that comes off from the back? anything else to check there?
-Could it be the catalytic converter? do I have to change that? or the oxygen sensor?

Sorry for any typos and thank you for all the help you are able to provide. I am able to provide pictures or answer any questions to make it more clear.
I am really stuck at that point.

Eli

[Somjuan]

I would bet it hasn't bled all the way. Elevate the front of the car up a few feet as permissible and bleed it again. Mine did the same as yours before I put in an expansion tank, it was awful to bleed. Might take a few tries.

[Lebindor]

Thank you John for the tip. I have tried this method before I installed the muffler and right after I installed the new thermostat. The temperature did not move and stayed at a bit below the center.
This morning and with the muffler on, I repeated this procedure with fan on and heat on all the way. The temperature was fine for around 30 minutes. I took the car for a quick ride 1-2 miles with the heat on and the temperature started to rise.
Do you have an idea why the temperature does not go up when the front is lifted ( i was applying gas as well when it was lifted)?
What should I be looking at next?

Thank you again all for your feedback. I really appreciate any tips if you have been through the same thing.

Eli

[Drew320]

Every time I pull off most of the coolant bits in the front, (radiator, thermostat, water pump pulley belt) I'll take a garden hose and run it through the inlet and outlet ports on the head and make sure the whole engine is getting a good flush, then I'll repeat for the radiator.
When the car overheats, are you getting just the reading from your cluster gauge? Or is the engine noticeably radiating heat from just standing over the engine?
I've had a gauge give me a faulty reading that it was overheating and I could stick my hand on the valve cover without burning myself.

[Lebindor]

I have flushed the radiator with the hose. The water going in from the top was gushing from the bottom. Right now i am relying on the reading from the cluster gauge.
To flush the engine block where do you put the hose?on the hose that goes from the top radiator and repeat on the hose that comes out of the top thermostat?
I assume you keep the heat on all the way as well.
How do you ensure all water is drained from the engine after that?
I am still intrigued on why it does NOT heat when its jacked up?
Thank you for your help again.
Eli

[Lebindor]

So tonight I have tried the following:
1- parked on a hill nose up and repeated the bleeding procedure. Car overheated to 3/4 and stayed there
2- drove downhill to get gas, temp needle moved to center
3- drove back up at same speed, temp back to 3/4
4- removed connectors behind the cluster and cleaned and same thing
Few things i noticed:
1- the faster i go the cooler it gets
2-after i parked my car the top radiator hose seemed like it built pressure, what does that mean?
3- what should i be looking at next?
Thank you for all help. I am in need to fix this
Eli

[okieflats]

When I had my overheating issue it was simply mineral type deposits in the radiator restricting flow through the tubes. Flushing with a hose is not adequate to rectify that.

Sign of inadequate radiator cooling due to internal corrosion deposits or simply undersized is overheating driving up steep hill on a hot day.

That is not to say you need a new radiator, but in my case that's what I needed. I got it professionally cleaned by having it "rodded-out" but then it went bad again shortly after that, so i got a new one, and even opted for more tubes (an XL core = more tubes and cooling capability) and that was the long term fix for me.

[Lebindor]

I was planning to do that next. Do you have a link for the radiator you used XL? Was it a direct fit?
I am changing my radiator cap and my breather PVC hoses to make sure I am not running too lean and overheating.
Any other tips?

Eli

[charter21p5]

My e21 had a similar issue as yours. Fixing it is really about good coolant, good known working coolant system parts, free flowing coolant in the system and bleeding the system. That sounds very simple however my experience it wasn't as simple as it should have been.

Do you have a thermal camera?

I can help you resolve this as I spent roughly a few months ,obviously not dedicated time, researching and testing this until resolution. Epmedia was really helpful with information and keeping me pointed in the right direction.

[Lebindor]

Hi Robert, thank you for your feedback.
Can you let me know the method you used to bleed your system?
I am trying the least expensive methods first to diagnose and potentially fix,
So far I have done the following:
1-Changed coolant, I am using Preston pre-mixed 50/50
2-Changed thermostat
3-Flushed radiator with hose, but it seems that some are saying it could still be clogged
4-Changed the rad cap this morning and coolant was overflowing from the small bleed tube. Temp up to 3/4

My next steps are in this order:
1-Change the temperature sensor
2-Change the radiator

After that I am out of thoughts on what to do next. I do not have a thermal camera. I will look on amazon to see if I can get an inexpensive one.
Thank you again

[charter21p5]

You bet! If you don't mind check out this thread first then let's re-sync on your system. https://www.bimmerforums.com/forum/s...ies-to-the-E21

Also your local fire department has a thermal imager. I borrowed my local FD imager before I bought one.

I will help you get your coolant system back to baseline.

Are you located in NC by chance? If so you could borrow my thermal imager.

Robert

[Lebindor]

Hi Robert,

I am in the process of borowing a camera. I have read your thread and just read it again. Have you been able to go back to below the half mark?

Eli

[charter21p5]

Yes, it took some time. Ideally you want to know what the temperature of the coolant system is for example the radiator, upper radiator hose, lower radiator hose.you should have a 30 degree drop from upper to lower radiator hoses. I found I had a much larger drop which led me to believe my radiator was gunked up from 30 years of service and this was the case.

I took my radiator to a radiator shop that used a glass bead cleaning system on it.

I also found my heater core was also the same.

Knowing the temps will give you a baseline for the system effectiveness and tell you what the temp sensor / temp gauge is reading. Then refer to my previous thread asking for assistance with the temp sensor.

[Thecatmilton]

You may want to check or replace your water pump. When mine started leaking at the shaft seal, I replaced it. The impeller fins were rusty and most were almost completely blocked. The car had ran hot a few times before that and stopped doing so afterwords.

The radiator may also be an issue. The all metal spectra premium radiators are pretty good.

[Lebindor]

I am trying the simple items first. I will test the temperature using the thermal camera once I get it. In the mean time:
1- I am changing all PCV hoses to make sure I am not running too lean
2- I have ordered another 71 dec C thermostat
3-I also ordered another water pump-I do not want to change it unless necessary but might just do so to eliminate this variable all together.

Robert, i do not think it is the heater core. I can by pass it and bleed the system to check. or can I just bleed the system with the temperature on cold?

Eli

[charter21p5]

Once you are sure flow and temp drop across the radiator is good then I would recommend jacking up the front end while bleeding the system, or do what I also did and buy a coolant system filler based on vacuum. Ecstuning makes a $90 schwaben tool just for this purpose. Basically make sure the coolant system is air free. I had a heck of a time with this and the solution was, after the coolant system was in order, to either jack up the front end or use the coolant fill tool.

And yes theoretically if you close the heater control valve or plug it off from the main system you could then test it to confirm operation but if it was me do what I said above.

If I recall the hcv only blocks flow by closing one coolant line towards the heater core. There are 2 coolant lines going towards the heater core.

Also make sure your temp sensor is accurate based on my other thread and using the thermal imager.

I assume you have an air compressor, is so seriously consider getting one of these types of tools: https://www.ecstuning.com/b-schwaben-parts/coolant-refill-air-purge-tool/003466sch01/

I just noticed they are having a major sale on them!

[Lebindor]

I will check the temperature as soon as I have my hands on a temp gauge. This will allow me to determine if I have a faulty temp gauge as you mentioned.
Thank you
Eli

[epmedia]

Hi Eli. The OE t-stat opening temp is 80c(176f), I feel the 71c(160f) is rather cold, especially during the winter months. If yo want a cooler t-stat, I'd rather go with the 75c(167f). I have the 75c in my '78 (2.0l), my opinion it's great during the summer months, but a tad too cold for the winter months. A cooler t-stat does not prevent overheat - it only delays it for a few minutes.

Yes - make sure that temp gauge is reading accurate (middle should be about 180f).
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You say when radiator cap replaced, the coolant was running out of the bleed tube? Was this with the cap installed and pressurized, or just spillage while replacing the rad cap?
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If needed: the Spectra Premium is a good radiator and good price. All metal, repairable, etc. This fits Automatic and Manual transmission e21 320i:
http://www.rockauto.com/en/moreinfo....011520&jsn=375
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This is a short story of running lean and excess engine coolant temp: Once on a hot summer day, my engine was running hotter than usual and running like crap at idle and stop-n-go traffic. Over the past few months I had been enriching the fuel mix a tiny bit so the engine would start normally. It finally dawned on me that the fuel filter was past-due for replacement (my fuel tanks are rusty-dusty). I replaced the fuel filter and the engine coolant temps returned to their normal. Of course I also had to re-set the fuel mix.

If the ignition timing is improper, this can also contribute to over heating. Make sure the distributor is clamped tightly after checking the ignition timing.
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I've not had to raise the front to bleed the coolant, but it is a good method. I use a no-spill funnel contraption (funnel and piece of hose for seal). Beginning with cold coolant and heater on full hot, and heater fan on LOW, and engine idling; Keep the coolant level above the radiator neck(prefer funnel filled a few inches) while squeezing/massaging the rad hoses. You'll eventually notice when the upper hose starts to get hot, this is when the t-stat begins to open. While the t-stat is opening -you may notice more air bubbles releasing into the no-spill funnel, you can give the engine a few 'little' revs while watching for air bubbles. After the t-stat has opened and all air bubbles 'visually' expelled, you can switch the heater fan to higher speed and test the heater's efficiency. When you are satisfied all the air bubbles are out, you 'should' be done bleeding the coolant system.

Just some notes: I've used the no-spill funnel on engines with bad head gasket and cracked heads before too. Be extremely careful if suspected leaky head gasket because coolant can get hot quickly and spray out of the radiator unexpectedly. Using the no-spill funnel method; Beginning with cold coolant, coolant previously bled (or bleed attempt), and coolant level above the radiator neck(prefer funnel filled a few inches); watch for air bubbles while 'blipping' the throttle really quick (as much as you can open the throttle, as quickly as you can, without revving the engine very much). This quick throttle 'blipping' simulates a small engine load by making more pressure in the combustion chambers. Be aware that cavitation(from fast rpms) and boiling will also make some bubbles, especially while the coolant is not pressurized.

*If you don't want to use the no-spill funnel method to test for combustion gasses in the coolant - there are test kits avail from the local auto stores (I've never used one).
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Hope this helps with your t-shooting. Be safe and welcome to the forums!

[Lebindor]

Hi Charter,
So my plans on borrowing a thermal camera failed so i bought an inexpensive infrared thermal gun in hopes to get an idea. I will let you know what i get so hopefully my temp sensor is accurate.
Hi the catmilton
My water pump is not leaking but I will keep that in mind, you and Robert are suggesting the Spectra rad so I think I am going to go ahead and purchase it.

Hi Robert,

I will definetly try the thermal gun first and check if my temp gauge is accurate. The cap was leaking after being pressurized.
I am changing all my PCV hoses and the fuel filter after your suggestion. Planning to do an oil and filter change as well. I was hoping to change one thing at a time to pin point the problem but it might save me time just to overhaul the entire system. I also bought a waterpump just in case but will be changing the radiator first just because it is much faster.
I will follow your bleeding advice and let you know how it works.

Thank you all for your advice
I will keep you posted
Eli

[320iAman]

I had similar problems, removed the auxiliary fan from front of radiator and temperature went down. I also changed the fan from 80-83 one to the smaller 77-79 one and installed the bmw fan shroud--this gives vacuum-which pulls the air thru better for better cooling--80-83's dont have a fan shroud and vacuum pulling of air thru radiator core is lacking much.

Another way to keep the auxiliary fan is connect a switch too it--using a double 6.3 mm female spade terminal(standard for these cars) setup-run wires and install switch in the Cab of the car,, when the gauge goes up past 1/2 on temperature gauge-which is normal for these cars-flip the switch on, the switch must be rated for 30 amps or better, an easy 2 wire connection that uses stock wiring on the car with the Auxiliary relay and Auxiliary fuse in fuse box.

One more item--I installed an overflow system--instead of venting pressure and coolant to the atmosphere--down the side of the radiator-I installed a coolant line from Radiator cap neck to overflow bottle--this way the dual action of radiator caps keeps the radiator full to the brim with water and coolant--overflow bottle is universal and attachs to the front of the car sheet metal that has holes in it--you can get quite sophisticated with the overflow bottle--stainless steel for looks and so forth. When radiators lose coolant-water more precisely--they get too hot and engine as well.

Randy

[Lebindor]

Thanks Randy I will consider your suggestion. I have the AC too so maybe I should eliminate that. I am trying first to go back to normal temp with the current set up aince I know it is possible because I had it. Also the small bleed tube should it hang free near the radiator? There is a small metal tube with the aame size that seems to connect to that tube?? What is it for?

Thank you again
Eli

[epmedia]

Thanks Randy I will consider your suggestion. I have the AC too so maybe I should eliminate that. I am trying first to go back to normal temp with the current set up aince I know it is possible because I had it. Also the small bleed tube should it hang free near the radiator? There is a small metal tube with the aame size that seems to connect to that tube?? What is it for?

Thank you again
Eli

I think the small metal tube you speak of is the fuel tank(s) vent line - Someone may have disconnected it from the charcoal canister?

The radiator vent(bleed) hose drains to the deck (open to the atmosphere, unless coolant recovery(overflow) tank installed).

The cap was leaking after being pressurized.

Is this a new 15-16psi cap? More specifically, was the cap leaking because bad seal, or was it leaking out of the vent(bleed) tube/hose because the cooling system reached 15-16psi? Do the radiator hoses get hard to squeeze before it reaches normal operating temp?

The coolant recovery(overflow) bottle that Randy mentions is a great idea for all e21's.

[Lebindor]

HI Robert,

interesting. Do you know its location? perhaps some one has a picture of their set up?
It is not urgent unless it has any contribution to fuel mixture/overheating
Thank you again.

Eli

[epmedia]

You can see the hose on the radiator's neck here. The other end of this hose is routed down, outside of the radiator, which is also in the picture.
http://www.realoem.com/bmw/enUS/show...diagId=11_0633
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The charcoal canister is originally under the battery tray. If the fuel vent system is clogged/closed, this could cause fuel delivery issues if the fuel tank(s) pressure drops below atmospheric pressure. The steel 'fuel vent pipe' runs along the passenger side(NA) of the car, and along the bottom of the radiator, stopping next to the driver side(NA) of the bottom of the radiator.

In this pic (a 1978, a tad different than yours), I have a pressure(test) hose attached to the end of the steel 'fuel vent pipe' (way down there).

click to enlarge
(disregard the piece of rubber that's wrapped on the k-jet pipe)
pressurize.jpg

[sbcrockett]

Hi Eli,

I'm a little late getting to the party on this one and I really don't have anything technical to add. What has worked for me EVERY time when I drain and fill the coolant is jack up the front (or park with the nose up), heater valve all the way open with the fan running, as others have mentioned and fill it slow. I'm talking SLOW, like barely a stream. I just wanted to emphasize that once again before you decide to go on an overhaul adventure needlessly.

Best of luck!

Steve