[OB_NB]

I’m looking for any suggestions before I bring it in and have it professionally diagnosed.

Car: 2005 330i ZHP
Engine: 2003 M3 S54 116k miles

Brand new parts:
Water Pump
Thermostat
All hoses including heater core hoses
All seals
Expansion tank and connecting pieces
Radiator
Electric fan

Symptoms:
The cooling system seems to be over pressurizing and the car is running hot/will overheat. The car is running between 80C-90C when cruising around but when I romp on it, the temp will continue to climb past 99C before I shut it off.

First, the coolant was just coming from the cap so I replaced the cap. Then my brand new radiator plastic end cracked and I lost all my coolant and had it towed home. I replaced the radiator with an aluminum 3-core radiator but the problem continues.

The hoses are rock solid and even bubbled around the hose clamps. The pressure is so high that it caused coolant to drip out of the upper hose o-ring.

The electric fan is kicking on at proper temps and does lower the temp quite a bit.

I did a compression and leakdown test. Compression was all 165-175. Leakdown was all less than 10% I also pressurized the cooling system and it held 20psi for the entire hour the tester was on.

It runs incredible, pulls super hard, idles perfect and starts every time

I’m out of ideas. I know that it’s impossible to diagnose over the internet but I wanted to give you guys a try before throwing in the towel. I’ve done almost 100% of this swap myself and don’t want to give up on the last little bit.



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[WOLFN8TR]

I’m currently dealing with the same exact problem. Bled the system several times. Runs great and doesn’t over heat. The other day it was 105 and coolant temps were 195-200. The car has never overheated since taking ownership 3 years ago.

All new cooling system. Water pump, Tstat, Hoses, Koyorad Radiator, Spal 2082 Fan and Viton Orings.

Is it possible to have a suction leak before the water pump on the two hard lines that have two small orings but not loose coolant? Reason being is the two orings that came with my new water pump from ECSTUNING were two different sizes, 18x3 and 16x3mm, number 12 on the diagram. They are both 18x3mm. I wonder if the smaller one is allowing the system to suck air? I didn’t catch this until after it was all together.

https://www.realoem.com/bmw/enUS/sho...diagId=11_3011

[OB_NB]

I was wondering the same thing about those 2 rings. I ordered the original set from FCP but accidentally crushed one when installing it. When I replaced them, I ordered a set from the Indy shop up the street and it was way easier to put back together than the rings from FCP but I didn’t think to compare them.

EDIT - I thought you were talking about the rings on the back of the thermostat housing, part number 11537830709 or number 13 in the diagram.

Are there 2 rings that go on to that pipe?? I think I remember seeing/having only 1?

EDIT #2 - I see the 2 rings. I did replace them both at one time but it might be leaking air into the system still. Ill have to pull it all apart.. again

[WOLFN8TR]

I have a feeling that’s the problem. Mine went together easy as well with very little resistance. I have a feeling the smaller one (16x3) just before the water pump is sucking air, the one on the left in your photo. UGH...

EDIT: The small pipe behind the water pump has two orings 38x3mm.

https://www.realoem.com/bmw/enUS/sho...diagId=11_3010

[OB_NB]

Update: Bad head gasket. They found that the cooling system was spiking to 30psi after starting it and they found gas in the coolant.


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[Braymond141]

I had over pressurization issues when "upgrading" to a CSF radiator. Got sick of it and went back to stock and never had an issue again.

Sounds like you got your answer though.

[HDdave]

Originally Posted by OB_NB

Update: Bad head gasket. They found that the cooling system was spiking to 30psi after starting it and they found gas in the coolant.


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Dang.. That sucks about the head gasket! It seems like this issue is not as common as rod bearing failures though- correct?

Only reason I bring that up- Is that I have read about failed head gaskets completely ruining s54 blocks pitting them out in between cylinders.. This was a common problem on LLY duramax engines as well (especially with any added power). So the common practice was to just go on ahead and do it as preventative maintenance, or at the very least be mentally and financially prepared for them to fail. Replace with ARP studs/ factory gasket- problem solved and/ or prevented.

Is this something that should be considered with the S54 as well? Head stud and gasket job now seems a lot better than a ruined block, same as fresh rod bearings now sound better than a trashed engine...

[Mr.wReckless]

From my understanding, the block is cast iron and quite sturdy and usually survives well with overheat conditions and blown head gaskets. The head is aluminum and doesn't fare so well under similar circumstances and will much more easily warp and require skimming to get a flat underside again.

Also I've heard/read that the S54 block was cast from the standard 3 litre block at the time and then bored up to 3.2 hence leaving thinner walls between cylinders and head gaskets leaving the latter a bit more vulnerable than the standard 3 litre block.

Regards

[OB_NB]

From what I can tell, S54 headgasket issues aren’t common at all. The rod bearing issue is definitely worse.
When I had the engine out I did rod bearings and all new gaskets and seals. There was nothing odd that indicated any type of failure. The compression and leakdown tests were great. All of this is making me think that the damage is minimal. Hopefully no block issues


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[Andrebxp]

Originally Posted by Mr.wReckless

Also I've heard/read that the S54 block was cast from the standard 3 litre block at the time and then bored up to 3.2 hence leaving thinner walls between cylinders and head gaskets leaving the latter a bit more vulnerable than the standard 3 litre block.

Regards

While I'm not sure of how they manufactured it, it is a bored out 3.0L.

Instead of designing a new block they just reused the existing M5x block design. A new block design would have made the car too expensive to manufacture.

My original engine blew up due to the headgasket failing between 5-6. The block's deck was fine but I needed a new head. Had about 164k at the time.