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Discussion Starter #1
Hello Ladies and Gentlemen.

I've recently purchased a BMW 328i SE built October 1995. The best way is for me to list the symptoms and hope one of you has seen this before:

-At idle the car does not overheat. Sits in the middle even if ticking for an hour or more.

-When driving the car overheats within 4 or 5 minutes, even when driving softly.

-But, even with the car stationary but being revved at 2 - 3k, no overheating.

-Heaters are cold/cool at all times- although maybe slightly warmer than the outside air.

-After (an attempt at) bleeding the system today there is steam coming out of the bleed screw at normal temperature and when the engine is hot.

-Top hose warm, bottom hose cool.

The thing that has thrown me is that it's ONLY when the car is MOVING. Even sitting on the drive and revving the car in a manner which reflects driving (revs up and down, and then held at 2k) it doesn't get hot.

The problem starts the minute I am moving.

I'm going to change the thermostat tomorrow just because I've bought one and it might help, but given the odd symptoms I can't see it will fix the problem. Surely it should overheat most when being revved while the car is stationary?

Any advice or things to rty would be most helpful. After looking at a few other posts I've noticed people's cars overheating, but not solely when in motion. Really strange.

Anyway, I look forward to hearing any of your opinions.

Best Regards,

Ian.
 

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Its like the engine is over compensating for the cold air coming in........but as you said, Really Strange. I'm wondering if there is some kind of friction occuring when in motion, but I would have NO idea where to even begin looking
 

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Check water pump,,make sure you can see the coolant being squirted into the expansion tank,if not then def water pump.Impeller prone to breaking up on early models hence fit the ali impeller....good luck
 

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Discussion Starter #5
Sukybm: I'm not losing any coolant out of it if that's what you're asking. It seems OK on that front. In fact I'm not losing any coolant at all.

Gazncaz: I'm wondering if this would only cause a problem when the car is in motion though? Is there any reason that the water pump would be working when the car is stationary and not when it's moving?

I'm changing the thermostat now, so I'll see if that helps, if not, I'll check the water pump and hope that eliminates the problem.
 

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Try a bleed first :thumbsup Take care not to overheat these engines,they can be a PITA if the HG goes.........

How to bleed the cooling system.
1.Jack the front of the vehicle up onto stands as high as possible,
2.Turn the ignition on to Aux 2, Engine OFF, heater on fan setting 1 and temperature fully hot,
3.Remove the rad cap/expansion cap,remove the bleed screw from the radiator and IF you have them the bleed screw(s) from the thermostat housing/top hose, return pipe or EGR thermostat.
4.Fill the radiator/expansion tank up and keep pouring till there are no more air bubbles coming out from the bleeds, using a funnel that fits tight in the expansion tank neck and filling it full of water will help push any troublesome air out, when good you can then install the bleeds and tighten down(don't snap them),ensure the rubber O-rings/seals are still on the screws/on the bleed holes.
5.Suck some water out so it's not full to the brim, start the car up and check coolant shoots out of the small hole on the inside of the expansion tank neck when the revs are held up, if it does then replace the cap and then run the car up and check for heat from the vents when the car is warm, then carry on and check if over heating still persists. You may have to bleed troublesome cars again afterwards.(but very rare).
6.If all is good then check the water level again in the morning when cool.

or

Ignition on, heater set to hot, bleed screw out.
Pull the top hose off the radiator. Pour coolant SLOWLY down the rad hose a litre at a time. When the coolant is building up in the hose, hold it above the level of the rad hose stub and keep adding it. When coolant starts to dribble from the rad, refit the hose. You may find that coolant starts to overflow from the rad cap orifice - if it does, just screw the cap back on. Once you've done that, the engine and radiator are full of coolant - the little air pockets that might be left will come through the bleed screw.

After the vehicle is bled you should check that when the revs are held up you get a flow of coolant shooting out of the hole in the inside of the expansion tank neck, this will help tell you if the water pump is circulating, then run the car up and check the lower radiator hose gets hot. You could also get a "block test" performed to tell you whether the headgasket has gone
 

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Discussion Starter #7
OK, here's how it went.

Thermostat I couldn't do because (and despite buying the right tool) the fan bolt wouldn't come off using brute force / a hammer / swearing. It was on so tight that I snapped a screwdriver in half while it was holding the bolts.

I decided to bleed the system. This all seemed to go OK.

However, when checking for water shooting out of the little hole in the expansion tank neck there was none. So I'm assuming the water pump is shot right?

Still cold air coming out of the heaters too.

So, a couple of further questions:

1) Where's the water pump? Is it attched to the back of the fan that I can't get off?

2) Even if I do all this, it doesn't solve the issue of the car only overheating when I'm moving, and not on tickover or revving while stationary. If I take it to a mechanic to have it done, he'll change all the bits, leave it ticking, it won't over heat, I'll drive off, and wallop. Have some heat in your engine. So why is it only when I'm moving?

Proper frustrating.
 

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Waterpump is knackered-get one from GSF with metal impellars :thumbsup It heats up when moving cause the coolant isn't flowing around....Suggest you get if fixed asap cause the M52 block is not a good block to overheat..........
 

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Discussion Starter #9
StK, I think this is the route we are going to go down, but I would have thought that it would also overheat stationary? If the water pump is knackered it still doesn't seem to explian why the problem is only there when moving. I just can't see a logical explanation.

I'm gonna take her to a mechanic and get it done, even if it does defy logic.

Zem poxy Germans eh...
 

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Just a guess, but when it is stationary, even with a knackered water pump, the coolant is still circulating slowly due to the thermosyphon effect of hot water going into the radiator and cool water coming out of the bottom, and since the engine is idling it is not creating that much heat and the thermosyphon effect is sufficient to keep it cool, but when driving there is a lot more heat to remove and without the help of the pump the coolant cannot circulate through the radiator fast enough to remove this extra heat.
 

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^^^^ what he said :thumbsup When not moving coolant is still moving around but not as fast as it should so when you drive off the coolant doesn't flow fast enoguh and voila overheat :thumbsup IIRC a waterpump with metal impellars is around £25 from GSF
 

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StK, I think this is the route we are going to go down, but I would have thought that it would also overheat stationary? If the water pump is knackered it still doesn't seem to explian why the problem is only there when moving. I just can't see a logical explanation.

I'm gonna take her to a mechanic and get it done, even if it does defy logic.

Zem poxy Germans eh...

Let us know what the out come is !
 

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Discussion Starter #13
Benjamin, a good idea, and a decent thought process, but I did rev the car while it was stationary too, for quite some time, and the heat sat in the middle.

I know. That sounds all wrong doesn't it? But I've tried it a couple of times and to the same effect. It's not a fluke, it's truly the way it's going. Stationary, any revs, normal heat. Moving, even at low revs, too hot.

And all the while with no heat from the heaters.
 

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Benjamin, a good idea, and a decent thought process, but I did rev the car while it was stationary too, for quite some time, and the heat sat in the middle.

I know. That sounds all wrong doesn't it? But I've tried it a couple of times and to the same effect. It's not a fluke, it's truly the way it's going. Stationary, any revs, normal heat. Moving, even at low revs, too hot.

And all the while with no heat from the heaters.
Revving an engine in neutral exerts very little pressure on it compared to driving down the road.
 

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Another suggest could it be the thermostat not opening and letting the hot water out of the block ?
I have read (don't quote me) that when the thermostat breaks, it has a fail-safe mechanism where it stays open, therefore the symptoms would be that the engine stays too cool... but like I said, I am not certain! :)
 

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Discussion Starter #18
Revving an engine in neutral exerts very little pressure on it compared to driving down the road.
I do get that to a certain extent, but I drove at little more than tickover (5th gear, 1000rpm at 25mph style) and it got hot, yet I held it at 3k rpm on the drive and it's fine. I assume it's friction (between cylinders and pistons) and the process of combustion causing the heat I just would have thought there's more exertion at the 3k stationary than at 1k moving. I may be well wrong, I'm not an engineer of any sort.

I'm not naysaying, and I genuinely do appreciate the input and ideas, but I just feel that I've sort of eliminated that one.

However, these views and ideas will be relayed to my mechanic when I speak to him, and if any of you have any more nuggets of wisdom, throw them at me.

Thanks gents.

Ian.
 

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Discussion Starter #19
What does the temp gauge do?
The temp gauage sits in the middle when stationary, either at tickover (900ish rpm) or with the revs held at 3000rpm.

When driving (from cold) the temperature guage will go up to halfway at a normal speed, then sit at halfway for a minute, maybe two, and then rise from halfway to red light within about 40 seconds.

When driving from a warm engine the temp guage sits at middle for a minute or two, then spikes up to the red light within 40 seconds of creeping over the halfway point.
 

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Hello Ladies and Gentlemen.

I've recently purchased a BMW 328i SE built October 1995. The best way is for me to list the symptoms and hope one of you has seen this before:

-At idle the car does not overheat. Sits in the middle even if ticking for an hour or more.

-When driving the car overheats within 4 or 5 minutes, even when driving softly.

-But, even with the car stationary but being revved at 2 - 3k, no overheating.

-Heaters are cold/cool at all times- although maybe slightly warmer than the outside air.

-After (an attempt at) bleeding the system today there is steam coming out of the bleed screw at normal temperature and when the engine is hot.

-Top hose warm, bottom hose cool.

The thing that has thrown me is that it's ONLY when the car is MOVING. Even sitting on the drive and revving the car in a manner which reflects driving (revs up and down, and then held at 2k) it doesn't get hot.

The problem starts the minute I am moving.

I'm going to change the thermostat tomorrow just because I've bought one and it might help, but given the odd symptoms I can't see it will fix the problem. Surely it should overheat most when being revved while the car is stationary?

Any advice or things to rty would be most helpful. After looking at a few other posts I've noticed people's cars overheating, but not solely when in motion. Really strange.

Anyway, I look forward to hearing any of your opinions.

Best Regards,

Ian.
The temp gauage sits in the middle when stationary, either at tickover (900ish rpm) or with the revs held at 3000rpm.

When driving (from cold) the temperature guage will go up to halfway at a normal speed, then sit at halfway for a minute, maybe two, and then rise from halfway to red light within about 40 seconds.

When driving from a warm engine the temp guage sits at middle for a minute or two, then spikes up to the red light within 40 seconds of creeping over the halfway point.
Funnily enough, I know the exact symptoms your describing... Mines doing it to :( Although mine doesn't go into the red that quickly. Gets to the middle after about 2 mins of driving, but can sit there for sometimes a while, sometimes a couple of mins, then gradualy goes toward the red, not had the light come on as of yet though. Ive found if i boot it once it starts goin past the middle, and i mean proper boot it, it tends to cool it down, back to the middle :S

Mine had a new HG about 4k ago, new therm about 4.5k ago. and has not long hit 197k.

I managed to fix said symptoms a few days ago, through bleeding it repeatedly. It lasted 2 days. lol. This, along with a few other niggling problems is why mines betting broken for parts at end of month when tax is up.


I have read (don't quote me) that when the thermostat breaks, it has a fail-safe mechanism where it stays open, therefore the symptoms would be that the engine stays too cool... but like I said, I am not certain! :)
Possibly, my last therm was stuck open, not sure if it got stuck, or broke with a failsafe like your suggesting.
 
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