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Old 07-15-2012, 10:09 AM   #1
the_carp
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Unhappy *Urgent* Advise Required - ECU issue..? Overheating

Hi All,

Im looking for some help. I have a 2001 325ci coupe with 97k

Last month it was Overheating all the time, So i Took it to a garage who told me it was the Radiator was at fault, So i told them to repalace the radiator, i picked the car back up, and had the same problem! Massive coolant leak, this time the expantion bottle had burst! so We replaced the bottle, kept the engine running and sure enough Tank blew again. Build up of pressure? maybe

Later that day they called to say it was possibly the head gasket .

So We had the car pressure tested and everything was fine. Head gasket okay! weak but okay.

Then they said it was the fan causing th problem, would come on for 20 secs then switch off, causing the car to overheat, we connected the fan to a live feed and new fan worked but when connected the fan to the car and the fan dosnt work................. car overheats....?!?!?!

So they now want to send the car to a auto electrition as they belive the ECU is faulty.

Any one have any ideas or advice, as i just seem to be throwing money at it and getting no where.

Parts replaced -

Radiator
Fan belt
Expantion tank x 3
Fan
Radiator pipes
Bleed nipple

Thanks in advance

Ian
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Old 07-15-2012, 10:16 AM   #2
dmax
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At this point, I'd say buy all the other parts of the system and diy it...temp sensor, thermostat, and water pump. Besides ET, these things all fail...and therm will fail both open and closed.

All this stuff is easy to do...I think your shop took enough of your money fixing things that either weren't broken or not fixing the things that were.

It's just turning some bolts/nuts the right way and living with a little spilled coolant. Easy.

Read some cooling threads.

BTW, unlikely you went from this to head gasket issue...and honestly it sounds like the mechs are just guessing. Why would they replace radiator and not the ET while it was out anyway? SMH
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Old 07-15-2012, 10:39 AM   #3
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what kinda shop do you bring your car to? I'd be pissed that there just replacing parts based on assumption. You should demand that they fix the problem for less/free, b.c of the previous "repairs" they claimed you.
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Old 07-18-2012, 06:06 AM   #4
the_carp
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Originally Posted by dmax View Post
At this point, I'd say buy all the other parts of the system and diy it...temp sensor, thermostat, and water pump. Besides ET, these things all fail...and therm will fail both open and closed.

All this stuff is easy to do...I think your shop took enough of your money fixing things that either weren't broken or not fixing the things that were.

It's just turning some bolts/nuts the right way and living with a little spilled coolant. Easy.

Read some cooling threads.

BTW, unlikely you went from this to head gasket issue...and honestly it sounds like the mechs are just guessing. Why would they replace radiator and not the ET while it was out anyway? SMH
Hi DmAX

Thanks for getting back to be, Garage phoned last night to say that the fan was not working because the thermostat was stuck closed so that has now also been replaced. and added to the new parts list....

BBBUUUTTTT......... Guess what the car is still over heating.

And now hes telling me that its 110% the Cylinder head!

Im really at my wits end now.

Plesae help
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Old 07-18-2012, 06:22 AM   #5
TurnersInOz
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Hi Ian,
It really seems as though your shop does not know what the problem is. From your description above they are throwing parts at it hoping the problem goes away. Are you okay with accepting a fix like that?
It might also be worth while to better understand exactly what they are doing. For example, if they've replaced the components they have, how/was the system bled? This is a common thing the folks get wrong while doing cooling system work. If it isn't bled correctly it'll never be right and it'll keep overheating.
A blown head gasket will manifest itself in other ways. At this point I'd ask for a detailed explanation for why they think its blown. Have they done a compression or leak down test?
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Old 07-18-2012, 06:35 AM   #6
the_carp
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Hi Ian,
It really seems as though your shop does not know what the problem is. From your description above they are throwing parts at it hoping the problem goes away. Are you okay with accepting a fix like that?
It might also be worth while to better understand exactly what they are doing. For example, if they've replaced the components they have, how/was the system bled? This is a common thing the folks get wrong while doing cooling system work. If it isn't bled correctly it'll never be right and it'll keep overheating.
A blown head gasket will manifest itself in other ways. At this point I'd ask for a detailed explanation for why they think its blown. Have they done a compression or leak down test?
Hi,

Thanks for your reply. It seems to me they have no idea either now. I have nearly had the whole cooling system replaced & still no fix - I know how complicated the cooling system.

My biggest worry is it has been pressure tested and they said everything was okay!!!!!

They have also ran the changing colour dye through the system and it still runs BLUE............! I belive it should change colour if the cyclider head is faulty?

They say that the crack bust be soooo small that its not causing the dye to change colour.

Ian

Hence the reason im still so confused
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Old 07-18-2012, 06:36 AM   #7
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If head, you'd start off sputtering in the a.m. for a little bit...well, at least I did. I guess there are other symptoms, as I know the head can crack in a variety of different places...if it did.

Are you losing coolant? Also, have to say that when my head cracked, I lost a little bit of coolant, but I didn't overheat. I guess if the crack was big enough, air could be causing the WP to cavitate and not pump.

Also, the shop should have gotten a faulty therm code, so why didn't they get that the first time.

The guess from Turner could be right, though...as simple as bleeding properly. We know the shop is a little on the weak side, so wouldn't surprise me if it didn't bleed right.

Try following my alternative bleeding instructions, search me for " alternative bleeding, 4K rpm, 20 secs." Think they'll come up.
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Old 07-18-2012, 06:40 AM   #8
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...and have you had pulleys/belts checked? I doubt that's it, but the WP does need to be driven. If pulley or tensioner or belt, then you'd notice also that your steering seems harder.

Try bleeding yourself...and I hope your car makes it through the other side without overheating. If not, the WP is still in there, and again, from your list, they still haven't replaced the temp sensor on the lower cooling hose...which is a 1 min. diy you should try.

Also, tell us how it's overheating...just goes straight to overheating, or only in slow traffic, but not when you're moving? What are your specific overheating symptoms?
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Old 07-18-2012, 07:37 AM   #9
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Taking some guesses here, but I will put my comments out there for you to think about.

First make sure the cooling system is bled correctly. See Mango's cooling system thread in the sticky section, the first few lines on the forum.

Some of the original BMW water pumps had plastic vanes that would break and reduce the volume of coolant flow as well as the broken vane can block the cooling system passages.

Verify that the fan switch is in fact working.

If you have a mechanical fan, might consider replacing the fan clutch?

Suggest you check my signature below for the Hidden OBC menu where you can monitor the coolant temp directly on your dashboard.

Does your car run cooler once the car is moving continuously on a secondary road?

As for your expansion tanks exploding/breaking, sound like your shop may be over filling the expansion tank, they sound a bit BMW incompetent?

Good luck.
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Old 07-18-2012, 05:29 PM   #10
TurnersInOz
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Quote:
Originally Posted by the_carp View Post
Hi,

Thanks for your reply. It seems to me they have no idea either now. I have nearly had the whole cooling system replaced & still no fix - I know how complicated the cooling system.

My biggest worry is it has been pressure tested and they said everything was okay!!!!!

They have also ran the changing colour dye through the system and it still runs BLUE............! I belive it should change colour if the cyclider head is faulty?

They say that the crack bust be soooo small that its not causing the dye to change colour.

Ian

Hence the reason im still so confused
Hi Ian,
The cooling system isn't really complex, but work does need to be done correctly or you'll wind up chasing problems and never getting ahead. The entire system can be replaced easily in an afternoon.

DMax and JFOJ offer some very good points, definitely explore them.

If the shop pressure tested the system and found no leaks, bleeding would be #1.

I've not heard of using dye in the cooling system (A/C yes).

A blown head gasket or warped head could be the result of the overheating. This can be tested for by doing compression and/or leak down tests on each cylinder. Has this been done?

It might be a good time to stop, reset and start from the beginning.
Assuming the new components have been installed correctly, bleed the system, and do compression tests (leak down would be better) on every cylinder, noting the results.
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