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316 M10 cooling problems

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Supernaut View Drop Down
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    Posted: 22 Dec 2018 at 8:02pm
Where to start...

In August of last year, on a journey from Tipperary to Dublin, the cooling system in my 316 began to play up.  The needle would move towards the red, as if the car was going to overheat, but then jerk abruptly to the left, as if the engine had suddenly cooled down all of a shot.  This continued for 20 miles or so, until the needle moved right but didn't go into the red and stayed there for about the same distance.  When I moved off from the toll booth outside Kilkenny, the needle moved left, to below the halfway mark, and stayed there all the way home, a journey of approximately 75 miles.  

Over the next couple of days, I continued to experience problems.  Some days, everything was fine and other days, the temperature gauge would continue to fluctuate, as if my car was considering overheating but changed its mind.  Traffic conditions, outside temperature, speed made no difference - it was completely random.  The problems could start at motorway speeds but could disappear when stuck in a traffic jam, but the car never overheated.  

There was no coolant loss whatsoever at any stage - I checked the radiator daily before setting out on a journey.

The head gasket was found to be faulty, with the compression rings being the areas affected (two or three cylinders, I forget which).  I replaced the head gasket (getting the head skimmed also), the thermostat and the sender unit.  Things seemed to settle down - if anything, the engine was running below half-way and took a while to heat up.  On a journey to Tipperary last January in sub-zero temperatures (110 miles), it took the entire journey to reach the half-way mark on the temperature gauge.

This was the worst of my problems until a trip to a football match in Waterford on 8th June - the temperature gauge began to fluctuate again.  It was a hot day but, again, there was no set pattern - the temperature gauge would move towards the red and would then jerk left abruptly, as if the engine was heating and cooling rapidly.  Sometimes it would appear as if the engine was about to overheat but it never did.  Coming to the end of the journey, things appeared to settle down.  On arriving at my destination, I opened the bonnet and found that the bottom radiator hose was barely lukewarm, whereas the thermostat was too hot to leave your hand on it for more than a few minutes.  The two hoses above the thermostat were hot.  

After the match, I checked the radiator and found that it was full.  On my return journey to Dublin, there were no problems whatsoever - the temperature gauge never went past half way, and everything was fine over the weekend.  

Over the course of the summer, the problem kept coming and going - everything would be fine for about ten days and then it would rear its ugly head again.  During the heatwave, in July, on a journey into Dublin city centre and home (a sixteen-mile round trip), everything was fine.  Starting the car again, to make a journey of about a mile to withdraw money, the temperature gauge was near the red but didn't go any further.  Having parked the car, turned off the engine, withdrawn money from the ATM and started up again (probably about five minutes elapsed), the temperature began to drop, so that, on reaching my destination, the needle in the gauge was just below the half way mark.

Over the course of the summer, I replaced the radiator, water pump and thermostat again - always with new parts purchased from a BMW dealer.  Any improvement was only temporary - and very short term, in some cases.  The respite periods became shorter and shorter, until coolant started coming out of the overflow pipe.  The head was then taken off and was perfect to the naked eye, the only issue being that cylinder no. 4 was clean, whereas the other three showed normal signs of use.  I had the head pressure-tested and it was found to be fine.  I replaced all the gaskets and hoped that everything was sorted but, again, no joy.

In the course of my enquiries, one independent specialist said that, in his experience, the thermostats supplied by BMW were no good - fitting an E30 M3 thermostat had solved the same problem on a number of occasions for various customers down through the years.  He had seen new thermostats that, when tested, were found to be faulty - they worked fine in boiling water but didn't do the job they were supposed to do when they were actually fitted to the engine.  I found a South African BMW site on which the owner of an M10-engined 316 had the same problem but a new thermostat and sender unit eventually sorted it.

I obtained an M3 thermostat, as suggested by the specialist, and got it fitted.  I collected my car on Thursday and everything seemed fine.  Yesterday, the gauge went to roughly midway between the half and three-quarter mark - sometimes it seemed nearer to half, and sometimes nearer to three-quarters but, needless to say, watching the road was my main priority.  The needle never even reached three-quarters, however, so I felt that things were at last on the up.  Today, however, after a journey of about a mile, the needle almost touched three-quarters.  Returning to the car after about two hours, things seemed OK on my journey to the city centre (eight miles) in free-flowing traffic conditions. Unfortunately, the needle went past three-quarters and began to approach the red, with no fluctuations this time, although the car didn't overheat.  

I switched the engine off and left the car for about twenty minutes.  The engine had cooled to about half-way.  I started up again and started for home, but, after about five miles, the needle again was almost at the red area.  Again, I parked and this time, I checked the bottom radiator hose.  It was stone cold.  I left the car for roughly ten minutes, after which the temperature had dropped to below three-quarters, then drove about two miles to the internet café in which I'm typing this.

I've been here for an hour and fifty minutes, so that I should get home (a mile away) OK, God willing.  

The upshot of all this is that I've replaced the entire cooling system (twice, in the case of the head gasket and three times, in the case of the thermostat), the head is fine, but I'm still no nearer to getting the problem solved.  I've checked the BMW Classic website, to find that a remanufactured engine block is no longer available, although I've added it to my wishlist.  My dealer tells me that it's the same story with a short engine - that can't be got either.

If anyone could assist, it would be greatly appreciated.

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Paul.S View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Paul.S Quote  Post ReplyReply Direct Link To This Post Posted: 23 Dec 2018 at 8:47am
Have you replaced the coolant hoses ? I had a similar problem with a Volvo years ago and one of the hoses had deteriated inside causing an intermittent blockage, not visible from the outside.

The inner layer had separated from the cords in the centre allowing the coolant between the layers causing it to balloon and cause a blockage which came and went as it cooled down.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote NickDE Quote  Post ReplyReply Direct Link To This Post Posted: 23 Dec 2018 at 2:31pm
E30 instrument clusters can cause issues. Soldered joints weaken with age, plus there are two rechargeable batteries that fail and leak. They then cause strange issues, sometimes speedo, sometimes rev meter, on mine it was the MPG gauge. If you are confident the engine and cooling system itself is ok, it might be just the temp gauge messing with your head. The instrument cluster is reasonably easy to get out, then you need to find an electronics specialist who can sort any issues for you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Supernaut Quote  Post ReplyReply Direct Link To This Post Posted: 23 Dec 2018 at 7:26pm
Hi Nick,

This was suggested to me also.  I had the fuel & temperature gauges replaced in 2007 as a previous owner had superglued both - the temperature gauge presumably to mask the cooling issues that caused the head on the original engine to crack (necessitating the installation of a new short engine bought through my local dealer - this engine has done 103,000 miles since March of '07).  He superglued the fuel gauge presumably through sheer stupidity.

Anyway, I had the temperature gauge checked in September in case it was faulty.  At the same time, I had the head checked with a laser thermometer, which gave a reading of something around 97 degrees, so the temperature gauge appears to be telling the truth. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Supernaut Quote  Post ReplyReply Direct Link To This Post Posted: 23 Dec 2018 at 7:33pm
Hi Paul,

Many thanks for coming back to me.  The hoses were replaced at various intervals between May 2012 and February 2017, the bottom rad hose being the first to be replaced.  I've had the hoses checked for blockages at various stages over the last few months and nothing seemed amiss, but possible degradation of the hoses is worth bearing in mind as the temperature gauge was telling me that my car was running too hot but yet the bottom rad hose was ice cold.

I've also been considering that there may be a problem with the block - a crack or some perforation somewhere that's allowing air into the system to interfere with the flow of coolant.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote AndrewE Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 10:27am
The fact that one cylinder was 'clean' says that there has been water ingress, basically it's been steam cleaned. Pressure testing is only 100% effective when the head is heated to full working temperature which of course you can't do. That's when cracks really open up.

I would throw the head away and start again with another one. That's assuming the block isn't cracked of course - rare but not unheard of.

Neil on here (Automac) may have a very good used engine - that would be another solution. 

Before that, I would remove the instrument cluster and examine the SI board and make sure the brass nut on the back of the temp gauge is tight enough. If it's loose it will cause the gauge to fluctuate. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote NickDE Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 8:34pm
Originally posted by AndrewE AndrewE wrote:

The fact that one cylinder was 'clean' says that there has been water ingress, basically it's been steam cleaned. Pressure testing is only 100% effective when the head is heated to full working temperature which of course you can't do. That's when cracks really open up.

I would throw the head away and start again with another one. That's assuming the block isn't cracked of course - rare but not unheard of.

I missed that in the original post. I agree, one clean cylinder is a smoking gun. I had a 320i (different engine, similar technology though) that was losing water. No leak, nothing on multiple pressure tests, nothing three BMW Werkstatmeisters could find after checking the car for over an hour. Just the coolant kept disappearing. In the end it was a casting defect in the head that waited almost twenty years before developing into a crack that only opened with a hot engine. When we finally took the head off in desperation there was a beautifully clean number 5 cylinder.... 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Supernaut Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan 2019 at 3:51pm
Thanks for that, folks. 

My theory is that, while the engine wasn't losing coolant at first, the fact that the temperature was higher than it should have been led to the failure of the head gasket on cylinder no. 4.

The "clean" cylinder prompted me to replace the head gasket and, just to be on the safe side, replace the head bolts also - this was before I fitted the M3 thermostat.  Since then, I've had no coolant loss but the overheating problem has reappeared...

I'm going to have another look at the original thermostat, remove the thermostat from the housing and run the car for a few days (at the weekend) - in the hope of getting more information as to the source of the problem.  She'll take longer to heat up, obviously, but, if she then overheats, it's more than likely the block (or a strange casting problem), in which case I could be in the market for the replacement engine you mentioned.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote AndrewE Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jan 2019 at 2:59pm
Don't do that as the coolant will bypass and it will just cook itself.

Does it overheat at speed, or around town (under 30 mph)?
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Cabrio Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jan 2019 at 8:00pm
Most M10 E30s I have looked at were viscous or blocked rad related start there first
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Supernaut Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan 2019 at 7:52pm
I could have one day where everything seems normal and the next day I could have problems - overheating can occur at speed or around town.

What I'm doing is running the car to simulate a situation where the thermostat is open the whole time, so that the coolant will run down to the radiator.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Supernaut Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan 2019 at 7:54pm
The viscous fan coupling was replaced in 2012 and I put in a new radiator last summer.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Supernaut Quote  Post ReplyReply Direct Link To This Post Posted: 20 Feb 2019 at 6:48pm
An update on my initial thread.

I haven't been able to remove the thermostat completely from the housing, but I've been able to, for want of a better phrase, push it to one side, which simulates a situation where the thermostat is completely open.

Needless to say, the car takes ages to heat up - in fact, ninety minutes of urban driving brought the needle only barely out of the blue.  It's been seriously cold here, however, and we've had a lot of frost. 

However, the day I put up my initial request for assistance, the bottom rad hose was ice cold.  Now it's warm - how warm varies, possibly subject to driving conditions and the outside temperature, but it's a sign that coolant is circulating. 

I also replaced the heater control switch (the one that allows you to switch from hot to cold).  My car's heater hadn't given out hot air for ages.  However, my mother was a front seat passenger in the car and she noticed warm air circulating at her feet for the first time in years (literally!).

Based on my observations over a few hundred miles of driving, I'm thinking the problem could be thermostat-related.  Any thoughts on the subject would be very much appreciated - and thanks to everyone for their help so far.

I've found someone on a South African forum with the exact same problem - https://www.bmwfanatics.co.za/showthread.php?tid=58692&pid=1388918#pid1388918

A new sender unit (Echlin TS6061) seems to have sorted the problem out after he or she had replaced the thermostat with a new FEBI Bilstein unit, but I replaced the sender unit in August 2017 with a new item and the readings I got from the head would indicate that the sender unit is doing its job.

Having fitted three new thermostats, all purchased from my local BMW dealer but none of which solved the problem, I'm wondering how to get one that works. 


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