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E28 (1982 - 1988)

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  #1  
Old 07-22-2004, 12:49 AM
harry371 harry371 is offline
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Mein Auto: 1985 528i
Question Overheating problem

I just got an 85 528i and ive noticed that it overheats pretty quickly. Ive tried to figure out why but I'm getting low on ideas...

-The thermostat was just replaced
-Coolant hoses appear to be fine and tank is topped up
-Fan belt doesnt look frayed or cracked
-radiator was recently topped up
-There are no heavy grease deposits on the engine-its all pretty clean

The cylinder head has just been replaced and the whole thing serviced so it should be fine. I need to figure this out so I can hold my mechanic to his repair quote.


Any suggestions would be appreciated...
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  #2  
Old 07-31-2004, 09:03 PM
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16valex 16valex is offline
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You should first check your engine fan, this fan should turn on when the engine temperature reaches at a certain degree.
Alex
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  #3  
Old 08-25-2004, 09:37 AM
OLd Shape! OLd Shape! is offline
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Quote:
Originally Posted by 16valex
You should first check your engine fan, this fan should turn on when the engine temperature reaches at a certain degree.
Alex
Are you actually overheating, or is the guage telling you red. The two are not the same. The sender unit may be getting hot, but the lump might be safe......

We assume you overheat whilst driving? Whilst driving, the fan is only contributing 20% of the cooling. The draft thru the rad caused by fwd motion is doing the work.

I would take a look at bleeding the system. Just because the rad expansion tank looks full tells you nothing. Are you getting hot air thru the blower in the cabin, if you select it to be hot? If no hot air, then I am 100% sure it's going to need a bleed. I would still wager it's 80% going to need a bleed.
I bleed mine with the front wheels on ramps, to ensure the bleed valves on Rad. and on thermo housing are the highest points of the system. I have a rubber pipe, fits nicely in the expansion tank filer hole, in which I blow like a crazy fool with the bleed valves open, turning to close them as I blow. What looks like a full system will need 1.5 more litres of coolant!
Be careful when blowing into the system......you may get a blow-back. Projectile vomiting is not appreciated in the engine bay. If you swallow it, you might die.
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  #4  
Old 08-25-2004, 10:01 AM
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Desertnate Desertnate is offline
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In addition to the air in the line, what does the inside of the radiator itself look like? I had a similar problem with our Jeep. In addition to a thermostat that was intermittantly freezing up, it was discovered that the passages inside the radiator itself were really gunked up (yes, that is a techical term ) with mineral diposits and such. They have a way of breaking someof that stuff loose with small rods.

If your radiator is in good shape, and deposits are the cause it may be fixable. In our old Jeep the radiator was starting to rust away and puting rods in it would have been the end of the radiator...we had it replaced.
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  #5  
Old 08-25-2004, 03:38 PM
OLd Shape! OLd Shape! is offline
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Good grief!
jamming rods into a Rad! I hope they were soft nylon or similar.

Radiators have a way of lying to you. You can run a hose pipe (Water) thru them, it runs clear, you think that you have cleared all the gunk from them, in fact you may have just cleared a passageway through the gunk...the rad may still be gunked up. (Same principle applies to Domestic central heating too).
To check a rad is working, you need to remove the front grille of the car, so you can feel the rad. If there is cold spots, it's gunked. There of course should be cooler spots, that's what the rad is for, takes in hot gives out cooler...but the gunked up areas remain rather cool.

I have cleaned out the system with cleaning solvents, added to the coolant. Thing is, they do not dissolve the stuff, just loosen it, and lumps of gunk now get cornered in the thermostat house or the heater valves..or any other corner that is going to be harder to fix!
One day, I will try a Domestic Central heating cleaner, see if that fares any better.
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  #6  
Old 08-31-2004, 09:52 PM
r0n r0n is offline
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Could be the sensor

I just bought a 97 528i and asked him if it had over heating problems... He said yes and had all the records of the work done. Looking the at the dealer receipts the last thing that was change (on the third visit for the overheating) turned out to be the temp sensor. I live in one of the hotest areas in the SF bay area, my car never hits halfway, even in 1 hour of stop n go traffic.

Hope this helps...
-R
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  #7  
Old 10-19-2004, 06:34 AM
OLd Shape! OLd Shape! is offline
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Follow up.......what was the problem or is it still a problem?
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  #8  
Old 01-19-2010, 04:05 AM
Panzerleutnant Panzerleutnant is offline
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You know I have a similar problem, this morning the car went straight through the red... like it should have exploded, according to the temp gauge, but when I stopped to check it out, nothing seemed to be wrong, so I started it back up and it had corrected itself, so i continued to drive and it hasn't happened again. So, correct me if I'm wrong, but i'm thinking that it's the temp sensor that's rusted over or gunked up... does this make sense to anyone? If so, can you point me to how to get at the temp sensor in the rad?
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  #9  
Old 01-19-2010, 02:07 PM
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nyclad nyclad is offline
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Quote:
Originally Posted by Panzerleutnant View Post
You know I have a similar problem, this morning the car went straight through the red... like it should have exploded, according to the temp gauge, but when I stopped to check it out, nothing seemed to be wrong, so I started it back up and it had corrected itself, so i continued to drive and it hasn't happened again. So, correct me if I'm wrong, but i'm thinking that it's the temp sensor that's rusted over or gunked up... does this make sense to anyone? If so, can you point me to how to get at the temp sensor in the rad?

I had the same problem a few months ago, every now and then when I first started up in the mornings, it would go all the way into the red within 30 seconds of driving off. I'd pull over and shut off the engine and let it sit for a minute, and it would be just fine when I started it up again.

I also noticed on other times, it would take forever for the reading to get to normal operating temp. Usually when I pull into work (13 miles away by freeway) the needle would be barely in the normal operating temp, but on the cool side. I also had a P0128 code a few times, indicating coolant temp below operating levels. I cleared it the first time, thinking it was just because the engine was cold, having just started up.

After reading through these forums, I decided it was a thermostat going bad, but fortunately mostly jamming open (cooler) instead of shut (hot.) After replacing the termostat (not the temp sensor,) I had no such problems. The temperature needle goes to 12 o' clock (and stays there) usually within 1 minute of starting up and driving (versus 13 miles with the old thermostat.)

Do you have any codes (pending or currently active) for the coolant temperature?

Last edited by nyclad; 01-19-2010 at 06:55 PM.
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  #10  
Old 01-19-2010, 02:11 PM
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nyclad nyclad is offline
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Quote:
Originally Posted by Panzerleutnant View Post
If so, can you point me to how to get at the temp sensor in the rad?

If you wanted to check the temp sensor anyways, look to the left of the radiator, and downwards towards the lower radiator/water hose. There's a set of wires going to the sensor, which sits on a little housing on top of the lower radiator/water hose.

<a href="http://www.flickr.com/photos/98195240@N00/4289026816/" title="Temp sensor by stvchin, on Flickr"><img src="http://farm3.static.flickr.com/2730/4289026816_3d8f3e8569.jpg" width="430" height="500" alt="Temp sensor" /></a>

Last edited by nyclad; 01-19-2010 at 02:15 PM. Reason: added photo
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  #11  
Old 01-19-2010, 02:33 PM
Panzerleutnant Panzerleutnant is offline
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No. I don't have any codes. It did it once, and it cruised nicely all day, temp gauge sitting at 12 like you said. I dunno. I'll monitor and update.
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