Head gasket may have gone

[Cyant1fical]

Okay people I have a problem - M40B18
So my temperature gauge has been all over the shop these last few months it sits below the blue line before I start the car and then once it’s heated up it used to only sit at a quarter of the way up but these past few weeks I’ve just been taking it round the block to keep it going nicely, now I’ve noticed yesterday I took it out and the temperature was almost in the red now bare in mind where it sits when it’s cold or hot normally and think that was a problem the previous owner never sorted after swapping out the old engine, maybe the coding plug I don’t know but anyway less of that...

I have an oil leak, not a massive one but still can’t pin point where it’s coming from but I’ve been topping oil up, I’ve been keeping an eye on the coolant levels and I can’t see whether it’s went down or not, I can’t see if oil of mixing either gonna have a proper check when I get some free time and it’s bloody light, I do get white smoke out the exhaust but I think that may be because the engine is stone cold normally as it’s just sitting at the moment ticking once a week... I’ll drive it and even when it’s at temperature it won’t go hot no matter the when the dial is on the console, I haven’t taken it far like I say but I’ll always let it idle and heat up before I drive it because of the age of the engine I took it out to a meet at the end of October and since then it’s done no more than 5 miles just round the block keeping it living, the heat worked back then so I’m pretty much stuck? Anyone diagnose?

Also, does steal seal work? It’s not permanent it’s just for the next few months until I can source an engine to go in the car if someone can help with that as well... sorry for the long winded post but giving the best diagnosis as I can because I know head gaskets are pricey haha

[Brianmoooore]

From the above, I can't see anything definitely wrong except perhaps a duff thermostat. It'll be a rare M40 that has popped a head gasket.
Change the thermostat, check that the coolant anti freeze mix is up to strength and properly bled and go from there.
Your warm up procedure does more harm than good - start the engine, put your seat belt on, then drive it!
Don't go hitting the red line before it's fully warmed up, but otherwise, just drive as normal.
Things like steel seal are best avoided, largely because of their inability to discriminate between small gaps that shouldn't be there, and those that should.
Insufficient information to advise on the oil leak.
Coding plug doesn't affect the temp. gauge, just the tacho.

[Cyant1fical]

Thank you, I’m glad you’re very knowledgeable of this, now I said it’ll be the thermostat which I didn’t mention in the previous post but one of my friends who swapped the the e30 engine out didn’t think it could be that, it’s simple things that you always forget about, I’ll be straight on that when I get home! Thank you again and I’ll keep this post updated

[martauto]

How about the little brass nut behind the cluster Brian ?

Mart.

[Brianmoooore]

and then once it’s heated up it used to only sit at a quarter of the way up

This alone confirms that the 'stat needs attention - either the wrong one is fitted or it's faulty. Needle should settle half way across the gauge on a M40.
Loose brass nut will make the gauge read high, not lower.
While the 'stat housing is off, check that the bleed valve will unscrew and is not blocked.

[Cyant1fical]

Right so after the busy Christmas period I decided to pull the covers off and after checking the coolant level I have found that it is literally empty, as for the temp, once it gets hot it almost goes all the way to the top in the red?

[Cyant1fical]

I’ve checked the oil on the dup as well and it sits above the first circle in between the first and second tiny circles, and I haven’t needed to put anything in it for a while

[Brianmoooore]

If there's no coolant in the engine, then it's not surprising it gets hot!
Fill it up, following the correct bleeding procedure, and see what happens. Coolant loss could be a simple leak somewhere, or disappearing into the engine, of which the former is by far the most likely.
M40 oil consumption is normally so low that I wouldn't expect to be topping up between changes. It's when the oil level rises you need to be concerned.
Before these problems arose, what age and concentration of antifreeze was in the system?

[Cyant1fical]

That’s not what I’m saying, I topped everything up to correct levels after I purchased the car aha, this is what gave me the belief I may have had a gasket problem because I was losing oil and now the coolant has gone as well, so I’m gonna have to search for it now, the joys of owning cars eh haha, as far as I’m aware it was serviced correctly before I purchased it and that it still had the 2 year life promise, now the owners of the car have only driven just over 2000 miles in 18 years in this car so I have a feeling this is a lie! It did look lovely and clean inside the coolant when I checked it though, the oil was was the same

Am I being stupid or...? But what’s the former aha

[Brianmoooore]

Plenty of places the coolant can be going, other than via a failed head gasket, and a simple leak is often far from obvious.
The first thing you need to do is establish where the coolant is going, preferably by using a coolant system tester which uses air to pressurise the system at its running pressure (1.4 bar on most E30s) without the engine running. These can be bought for around £40 on ebay, and will uncover minor leaks on most cars which the owners were unaware of.
Check whether the carpet is wet against the front centre console on the LH side.

[Cyant1fical]

I’ve found the problem, the radiator has a leak in it just below where you fill up the coolant, I pressure checked it today and that’s my finding, still very suspicious of the thermostat though, this could be an issue in the future, I’ve found a brand new radiator for the car £105 from euro car parts. I’m going to look at a 325 compact though as this is the m50b25 I’ve been after, the only problem is where the sump is on this one, if I remember correctly for the swap you need a rear facing sump Dont you? As the engine in mine just sounds like it’s on it’s way out tbh, finding hard to breathe when it’s started and the idle is poor

Cars man the Bain of my life

[Brianmoooore]

All the bits of the M40 rad. are available separately, so you may be able to repair: http://2009.bmwfans.info/parts/catalog/ ... /radiator/
You are correct about the M50B25 sump. You need the one from an E34 or, IIRC, a 7 series one will also fit. You will need the alloy engine mount arms from the E36 though.

[Yeti]

be careful that's it not your radiator cap gone as when the cap fails the there is a cut out where it screws on to drain away and where it drains makes it look like the rad has failed when it hasn't. when the cap fails the system isn't pressurized causing the coolant to boil out the cap making it overheat and loose coolant.

I had this issue and fitted a new radiator days before I went to Germany. my car over heated 10 minutes from Calais and realized it was the cap. I had to keep my heaters on until I got to Germany to then go to the local scrappy and get one of a e36 which resolved the issue straight away.

note the E30 and E36 only have the right cap as they are set at 1.4 bar (140 shown on the cap)

[Cyant1fical]

This is similar to the rad cap I have if this is any help and yes it says 140 on the top of it... https://goo.gl/images/8gRBQu

Here is a video of the radiator I took when testing today, excuse the language haha https://ufile.io/jwxge

Yeti, I tested it today with an actul pressure tester where I filled up the rad with water instead of coolant as it’s expensive to just throw away, I put 1.4 bar through the pump and you can hear a hissing coming from the radiator, this is similar to the one I have if not the same one, looks pretty much the same...

https://www.eurocarparts.com/search/203 ... gLpGPD_BwE

[Brianmoooore]

https://www.eurocarparts.com/search/203 ... gLpGPD_BwE

As ever, much cheaper through the cp4l sister site, at £62.83 after discount.
Beware of second hand 1.4 bar pressure caps. Although they were subject to a safety recall in 1996, there are plenty of the originals still around, and if they are faulty, they will over pressurise the cooling system, making it fail at the weakest point. This is usually the electric heater valve, but could equally be an elderly radiator.

[Cyant1fical]

I don’t know if the video worked but the radiator is leaking water about half way down the radiator itself, can you point me in the right direction of a new cap? Also I’ve looked on CP4L and can’t find a radiator

[Brianmoooore]

Also I’ve looked on CP4L and can’t find a radiator

Same company as ECP, and same part numbers. Picked from the same shelves by the same personnel.
Any part number that works for ECP should also work for CP4L.
Pressure cap should be on there somewhere, or it isn't expensive from BMW.
Haven't asked for one lately, but if BMW's records don't show that yours has been replaced, then they should supply one FOC.

[Cyant1fical]

I’ve sourced the radiator thanks, it’s £62 including the jan12 discount code, it wasn’t coming up because the people who had the car before me switched the engine from an e36 so I’ve had to use my old reg code which had an m40b16 in, I can’t find the coolant cap though, so I’m going to phone my local Bmw see what they’re saying, thanks for the help guys and I’ll keep updated. I’m going to change the thermostat whilst I’m at it as mentioned above I’m suspicious of it anyway, just to be on the safe side, at least I’ll have access to it once the radiator is out because of where it sits on the engine. Bloody cars man, Bain of my life

[Cyant1fical]

Radiator is in, I’ve also switched out thermostat to be on the safe side, changed out the coolant and bled the system, the bleed screw being plastic though just snapped in the hole when I was does due to the temp though, how annoying and I cba to send the radiator back so I’ll just make do with what I’ve got for now until the engine swap... the temperature is sat as normal at 88 but the needle still doesn’t sit in the middle on the dash so I think it’s an actual problem with the instrument itself *sigh* I’ve found a couple of other problems with the engine since yesterday and to tell the truth I just can’t wait to get the bloody thing out and start a fresh, thanks for all the help guys you’ve been great.

[Brianmoooore]

The black plastic bleed screw was used on many BMW models from the E30 onwards, and is equally fragile on all of them - I carry one in the ashtray of my E39 at all times.
The early ones have a plain thread, and the later ones have a slot running along the thread, so that they bleed air more easily without unscrewing so much, but they are interchangeable. I'm sure your local BMW parts department will know exactly want you want without any more details than "plastic bleed screw".
To remove the broken one, heat the tip of a 1/4" flat blade screwdriver to just short of red hot, and push it into the top of the broken screw. Pull the blade out, let it cool, then use it to unscrew the remains.