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Discussion Starter #1 (Edited)
2004 325i base model, A/T, 106k miles. Purchased two months ago with car fax, no additional service records.

Unfortunately, it seems I have purchased a car that qualifies as consumer fraud from a small time seller that has an LLC dealership license but, advertises in the for sale by "owner" section on Craigslist . There's so many of these dealers on CL now it's hard to find a true private seller. Anyway, after finally resolving coolant leaking from waterpump, ET tank o-rings, ECT leak it's still loosing about 3-4 cups of coolant every other day. It's neen pressure tested cold, with and without dye. Checked for dye/leaks while running at operating temp and no leaks seen. Only thing I haven't tried is a new ET cap but, doubt that's the issue. My best guess is a cylinder head crack. I haven't pulled valve cover to check for loose head bolts yet.

Only signs are coolant loss with no external leak and idles rough on cold start for about 30 seconds. There is:
No white exhaust smoke at idle or under load (son followed me on drive to check)
No coolant in oil
No misfire codes
No overheating

I found this thread on this forum: http://www.bimmerfest.com/forums/showthread.php?p=6435453#post6435453
and I think Auto head describes the most likely scenario in reply #6

Considering using liquid glass: irontite ceramic seal, as I have no intention of paying $1400 (quoted locally) for a used, rebuilt, resurfaced head installed. Reason being is that based on advice from other BMW mechanics even if a good, used head is installed with time-serts in block holes .. there's a 50/50 chance the block is warped to due overheating.

Besides the coolant loss issue the A/C is leaking freon.. had it vac and filled twice and only blows cold for about two weeks. Seems like most threads point to the evaporator as the most likely suspect. Last mechanic used yellow a/c dye and he said monitor the condensation drip on ground as it may have dye in it which usually denotes evap leak. Did not see any dye in condensation drip and doesn't have a musky smell. So, may be schrader valves, compressor shaft or other area.

All comments, suggestions welcomed.
 

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TheMalibuMafia
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Sounds like you need vanos seals and you probably have a coolant leak on the heater core line on the side of the motor. Or a coolant leak in another place.
 

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Discussion Starter #3
Sounds like you need vanos seals and you probably have a coolant leak on the heater core line on the side of the motor. Or a coolant leak in another place.
Thanks MM.

I was also concerned about the plastic heater core line under the intake but, I don't see a leak there (dye tested) and neither does the mechanic I brought it to. A seemingly good local BMW mechanic showed me on a pulled engine (intake runners removed) that the plastic heat core tube usually leaks where it mates to the cylinder head. Pretty sh!tty engineering IMO but, it is what it is.

What makes you say the Vanos seals need replacing?
 

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It's been pressure tested cold
Have you been losing pressure here over couple of minutes?

Do a compression test, cheap and easy.
 

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Keeping it surreal
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Thanks MM.

What makes you say the Vanos seals need replacing?
If the engine has more than 25,000 miles, the VANOS seals are toast. Indisputable fact of BMW Life !
 

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Discussion Starter #6
At first I was doing all the repairs and testing myself. I rented a pressure tester from Autozone and didn't fit the ET cap so, I purchased a kit from Harbor Freight. I pressure tested cold and found leak at ETC o-ring, ET o-rings (bottom of tank), Small crack on upper radiator hose bleeder screw mount, water pump + thermostat area. Replaced o-rings, installed new WP and thermostat, replaced upper radiator hose. Inspected Behr Hella ET and no cracks found. Just a few days after purchase I suspected an cylinder head issue and I dove into researching E46 info (my first BMW). Many post stating best practice is to replace all coolant parts on an E46 at 100k mile mark. I agree with that but, I wanted to rule out a head gasket leak before purchasing and replacing all new coolant parts. Within two weeks the water-pump was leaking at the weep hole, which points to either a defective part or combustion gases stressing the coolant system with increased pressure or contamination.

After another new WP replacement I did a cold pressure test and could not get it to hold pressure but, being the HF pressure tester isn't the greatest quality I figured the tester pump itself may be failed. At this point I was fed up and took it to a trusted local mechanic who did a cold pressure test, leak check at operating temp and engine idling, leakdown test. He said the coolant system held pressure for 30 minutes. No bubbles in ET during leakdown test. Not sure if he did a compression test too but, I will ask him tomorrow. If not I will do a dry and wet compression test on it. Will also inspect spark plugs for wetness (coolant) or other fouling.

Is it common for the M54 engine and BMW engines in general to cold idle rough/lumpy for 30 seconds and then smooth out? Two mechanics told me it's very common and other European engines do the same. To me it's a sign of coolant being compressed out of the cylinder or compression loss until engine warms and seals the crack. As I stated before there is no white smoke seen from exhaust at idle or under load.
 

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Discussion Starter #7
If the engine has more than 25,000 miles, the VANOS seals are toast. Indisputable fact of BMW Life !
Many post on this subject. Here's one: http://www.e46fanatics.com/forum/showthread.php?t=872015

My engine doesn't seem to have any of those symptoms,
I am not surprised this is just another problem area with the M54 (and other BMW engines).
The E46 is equivalent to a great looking woman with big juggs but, no brains.
 

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He said the coolant system held pressure for 30 minutes.
I think your head gaskets are fine otherwise it wouldn't hold pressure.

So I think it's the expansion tank cap that is releasing the coolant. All the other parts are tested. Maybe it doesn't open at all at 2 bars and over-stresses the system or the water pump was a bad luck and the cap is releasing the coolant.

Is it common for the M54 engine and BMW engines in general to cold idle rough/lumpy for 30 seconds and then smooth out?
It's common to be loud for 30 sec but not rough.
 

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Discussion Starter #9 (Edited)
I think your head gaskets are fine otherwise it wouldn't hold pressure.

So I think it's the expansion tank cap that is releasing the coolant. All the other parts are tested. Maybe it doesn't open at all at 2 bars and over-stresses the system or the water pump was a bad luck and the cap is releasing the coolant.
It's common to be loud for 30 sec but not rough.
I forgot to mention that a few days after I purchased the car I did a block test on it at operating and no hydrocarbons were present. I previously posted this coolant loss issue in another forum and one reply said to do a block test at cold start until operating temp. Makes sense because doing it that way when considering a possible crack.. the crack at cold start will be open (releasing exhaust emissions) and then most likely close at higher temps.

A few days ago during a one hour highway trip coolant did overflow from ET cap and white spots were visible on air box and on frame above driver-side headlight. Isn't the cap designed to to that though if pressure elevates? (even though temp gauge stays in middle). Also, the last mechanic bled air out of coolant system through the bleeder screw while engine was running. He and I know the FSM procedure but, he stated that's not the best way to get air out. Conversely, I've read otherwise on other sites that if it isn't bled per FSM the float will always be low and appear to be a coolant loss issue.
 

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.....
Is it common for the M54 engine and BMW engines in general to cold idle rough/lumpy for 30 seconds and then smooth out? Two mechanics told me it's very common and other European engines do the same. To me it's a sign of coolant being compressed out of the cylinder or compression loss until engine warms and seals the crack.
There is a lot going on with the engine in the first 30-90 seconds of operation. It's a different operating mode from closed-loop fuelling to open-loop fuelling, and the SAP is also operating during that time. VANOS controls the EGR function on these engines and VANOS relies on oil viscosity, so when the oil is cool, it's a little thicker, so that can have an effect (especially if your cam position sensors are old). Rough operation could even be as simple as a lazy O2 sensor. It may be "common", it may or may not be "normal", but it may be a sign of an actual problem, or something totally unrelated.
 

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Discussion Starter #11 (Edited)
There is a lot going on with the engine in the first 30-90 seconds of operation. It's a different operating mode from closed-loop fuelling to open-loop fuelling, and the SAP is also operating during that time. VANOS controls the EGR function on these engines and VANOS relies on oil viscosity, so when the oil is cool, it's a little thicker, so that can have an effect (especially if your cam position sensors are old). Rough operation could even be as simple as a lazy O2 sensor. It may be "common", it may or may not be "normal", but it may be a sign of an actual problem, or something totally unrelated.
Sounds plausible. Car does have SEL (CEL) P0171 lean code that could be o2 sensor related. I recently removed worn out Disa valve o-ring and replaced it with a slighlty oversized one that I found on write-up in a BMW forum and it didn't stop CEL but, certainly has helped the engine to run better, more responsive.

I did a lot of research prior to and purchased a bottle of Irontite Ceramic Seal (sodium silicate/liquid glass). I plan to put in this weekend per the directions and hope to get 6 months or more of crack sealing out of it. I think in my engine's case it's a very early crack that shows no other signs of head gasket breach and liquid glass it usually very successful in that situation. I will by-pass the heater core and during the 24-48 hour air-dry phase remove water-pump, thermostat, block drain, disconnect upper and lower radiator hoses and remove spark plugs. Will post update.
 

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Discussion Starter #12
Traded car in and will never buy another one. Will stick to Japanese: better gas mileage, more reliable, lighter, better during city driving, parts are cheaper to replace, easier to work on.
 
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