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OP, if you have a decent sized air compressor you can do the leak down test yourself also. AutoZone now has leakdown testers for free rental.

(Not sure if the little 3 gallon pancake/hotdog compressors have enough capacity ... never tried with one.)
 

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Mech said lets order the tank so he can test for the HG integrity... I am guessing you cant test if you dont have a working coolant reservoir?
He wanted to have a running engine in order for the combustion gas to leak into the coolant tank for testing. without the tank, it's not easy to test for combustion gas in coolant, chemical-wise.
 

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A friend's 2003 325i had good compression numbers, but the leak down test showed leakage into the cooling system. Even the leak down numbers were good on that engine, but it had bubbles in the expansion tank from two or three different cylinders.
My wife had cracked 2 heads on one car (2000 323iT M52TU) and I must say the hair line crack was soooo small, at cool ambient temperature, that I doubted if the leak-down test can detect. But perhaps at very high PSI the test will create some air bubbles in the tank as you said.
(The second time she drove the car 2 or 3 miles with a ruptured tank, and this cracked the head and pulled 6 or 7 head bolts out of total 14 bolts. I did save the otherwise good engine though.

My favorite cracked head test: with a working coolant system, run the engine to operating temperature, and drive around the block for 20 minutes if you could, then shut down the engine for overnight. Next cool morning, remove each spark plug and look very carefully for condensation on the tip, on all of them one at a time.
 

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Discussion Starter · #25 ·
Thanks guys for the help... The more i read the more I find out what I dont know and its depressing... at the worst F%$^%# time too... I know there's never a GOOD time but this summer has been f%^#$ HELL in every way.

So my mech (and dont get me started on the all mech stories, it'll take days, for those of you wondering why am I giving this guy a second chance) just replied with this, after I told him we need to check the head gasket, do we still need the tank:

"You need the bottle, it cracked down the side which is common on an old BMW. A compression test won't tell you anything as the motor would have a miss in it if the head or head gasket has just a small failure. There is a kit you can get from Autozone or O'Reilly to test head gasket"
 

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Any update? If your car got so hot it split the overflow tank, then I would be seriously worried about the integrity of the engine at that point.

Your guy wants to do this the easy way, which is spend your money. Fix the expansion tank, then you can get a combustion tester to see if you have any exhaust gasses in your coolant.


It's not a bad plan, and I'm not fully versed on the reliability of the gas testers but I understand they work pretty well.

Be advised you're going to need a pretty significant overhaul at this point, including all the cooling system parts (water pump, thermostat, hoses, expansion tank, and fan) which isn't going to be cheap. And you still may find down the road as you drive that the head is warped.
 

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My Mobile Mech replaced a busted upper radiator hose (was basically falling off the low side)
This is the root cause of your overheat problem, and headache. So I would like to see a pic showing the lower end of the hose to see how did it fall off from the Tstat output port. I have a feeling the connector was not locked and it backed out instead of the connector broke off.
 

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Discussion Starter · #29 ·
Any update? If your car got so hot it split the overflow tank, then I would be seriously worried about the integrity of the engine at that point.

Your guy wants to do this the easy way, which is spend your money. Fix the expansion tank, then you can get a combustion tester to see if you have any exhaust gasses in your coolant.


It's not a bad plan, and I'm not fully versed on the reliability of the gas testers but I understand they work pretty well.

Be advised you're going to need a pretty significant overhaul at this point, including all the cooling system parts (water pump, thermostat, hoses, expansion tank, and fan) which isn't going to be cheap. And you still may find down the road as you drive that the head is warped.
Waiting on the tank so he can do the tests, probably in next few days, I will update as soon as I have any new news

I will tell him to do the

  • Compression test
  • Check for exhaust in coolant
  • He already said we should also replace thermostat but we'll see after these tests

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Discussion Starter · #30 ·
This is the root cause of your overheat problem, and headache. So I would like to see a pic showing the lower end of the hose to see how did it fall off from the Tstat output port. I have a feeling the connector was not locked and it backed out instead of the connector broke off.
I saw the bottom end of the hose basically dangling on the last day I drove it. He already replaced that part now.

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Discussion Starter · #31 ·
He has taken it apart to give me that prognosis last week


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He has taken it apart to give me that prognosis last week


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What are we supposed to decipher from a picture of the radiator cap hanging inside the air intake box and a picture of the air filter and top cover?

This is some honest feedback.

If you want a real answer as to what is involved for diagnosing the problems for your car, stop wasting your time and money into this mobile mechanic. It doesn't seem like you are too familiar with the cooling system, and your mobile mechanic isn't doing you any favors either.

Find a local independent shop that specializes in BMW's and take it over there for a real diagnosis and then based on cost you can either 1. spend the money and save the car or 2. cut your losses and find another car
 

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What are we supposed to decipher from a picture of the radiator cap hanging inside the air intake box and a picture of the air filter and top cover?
It easier to remove the whole air filter box together after removing the two 10mm bolts, for more space to check and work. Why he just remove the top housing and the filter? Maybe this is the Mobile method.
 

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It easier to remove the whole air filter box together after removing the two 10mm bolts, for more space to check and work. Why he just remove the top housing and the filter? Maybe this is the Mobile method.

I think he did it just for a bin to put parts in, lol.
 

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he should have swapped out the hose thats under the ET as that one (on my 330i) is a nightmare to get to but easy to damage just repo'ing other parts. ditch the mobile guy - they typically dont know BMW's - you have to make sure by pressing them in advance. you could also hit up the FB BMW groups for a local guy.
 

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I think a local Fanatic could help the OP out more than the mobile guy.


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Discussion Starter · #37 ·
I think a local Fanatic could help the OP out more than the mobile guy.


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I been consulting with him, he's really busy and he just told me to take it to the local shop so that's what I'll do.

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Discussion Starter · #38 ·
So the shop said the radiator was all messed up and the lower hose, so those have to be replaced first, cant even do the compression test and exhaust in coolant yet.

$500+ for installing the lower hose, new coolant (that I provided), and the diagnostics so far... seemed a little steep but...

And another $900 or so for the radiator and thermostat that goes with it, installed.

I'll know more Monday night hopefully.
 

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Are you still paying the mobile mechanic who initially messed the car up? Why? Unless you just don't have any time to do work to the car the cooling system job on these cars aren't hard to do at all. Anybody with a tool set and YouTube can work on E46. I wouldn't drop another single cent into this car until I confirmed it doesn't need a new engine. The Nissen's radiator from FCP is less than $100 and the lower hose is maybe $40-50. The labor isn't difficult at all.

I'm sure I can speak for everyone here in saying you're throwing a lot of money at a car that honestly might not ever run right again. There are ways to test compression without needing a fully operational cooling system as outlined in this thread. I'll also speak for everyone in saying unless you can work on these cars yourself it's not going to be worth it to continue dumping money in the vehicle. These cars are great when they are running right but they can be a bitch when they aren't.
 

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Some input on that red overheat light "turning itself off" as you continued driving. This also applies to the coolant temp guage.

When the coolant sensor is immersed in hot coolant it gives you an accurate reading. When you keep driving and blow all the coolant out, there is nothing but air around the sensor, thus it cools and tells you all is well magically. Meanwhile, in engine-land, the block and head are starting to melt.

The absolute right and ONLY course of action when the gauge is climbing and especially when a red overheat light goes on is to stop immediately. Period. It may have just cost you $5000 to learn this. It is in the owners manual.
 
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