m40 engine overheating

[jamiedo]

Hi all,
Have had a look through some of the threads to do with this problem but cant find the answer...

I have a 1993 518 / e34 / M40 engine 67k miles...

Its been off the road for a while as I've been doing alot of work to get it MOT ready (I told myself 3 weeks ot begin with, its been 13 months...)

It passed its MOT, but it is overheating. Have tried bleeding the air from the system, but today realised that the water is not getting hot (or even warm) in the radiator, or in the hose going from the bottom of the rad into the water pump (front of the engine block).

The water is heating the radiator matrix, so I assume the pump is working properly...

The Temp sensor seems to be working properly, and the thermostat was replaced when I changed the cylinder head...

HELP! Any ideas would really be appreciated.

[bubba966]

Sounds like you might have a partially or maybe mostly blocked/clogged radiator.

You might want to try flushing out the radiator from both in & out hoses on the radiator to try and blow out any crud that's in there. As it's most likely to be clogged in the inlet side of things run pressurized water from the radiator outlet so that it's pushing water backwards through the radiator to blow the crud out of the inlet. Then try it on the inlet to blow out the outlet. Do that a few times and you should get out as much as is going to be possible.

If that doesn't work you'll probably need a new radiator.

[whiskychaser]

Hi all,
Have had a look through some of the threads to do with this problem but cant find the answer...

I have a 1993 518 / e34 / M40 engine 67k miles...

Its been off the road for a while as I've been doing alot of work to get it MOT ready (I told myself 3 weeks ot begin with, its been 13 months...)

It passed its MOT, but it is overheating. Have tried bleeding the air from the system, but today realised that the water is not getting hot (or even warm) in the radiator, or in the hose going from the bottom of the rad into the water pump (front of the engine block).

The water is heating the radiator matrix, so I assume the pump is working properly...

The Temp sensor seems to be working properly, and the thermostat was replaced when I changed the cylinder head...

HELP! Any ideas would really be appreciated.

The bottom hose may take a while to get hot. The million dollar questions are:
1. Is the heater getting hot
2. Is the top hose getting hot

[e34.535i.sport]

Flush the rad then check get it all back together, Start it up and see if the upper adiater gets hot... If not you may have a faulty thermostat even if its been replaced.

When you bled the air did you have the heaters on full and do it facing uphill etc?

[jamiedo]

Hi all,
thanks for the responses so far.
The top hose and heater are getting hot... the bottom hose and rad are stone cold...

When I bled the system I had the heaters on full, but no hills to use... I'll try flushing the rad and sticking the front on axle stands when I bleed it through.

I'll let you know how I get on - thanks again for the ideas...
J

[jamiedo]

So... I checked the rad - no sign of blockage. Changed the thermostat, started as normal - bleeding air with engine running etc.

The rad and bottom hose are now getting hot. But... as the temp guage started to go just over the middle (12 o clock) I bled the air again, and it was nothing but steam... Is this just something that happens when the engine reaches a certain pressure, or is this a problem?

From the sound of it the water pump bearing is making some crunchy noises, so I'll be changing that in the next few weeks - could this lead to the problem?

[DaveVoorhis]

as the temp guage started to go just over the middle (12 o clock) I bled the air again, and it was nothing but steam... Is this just something that happens when the engine reaches a certain pressure, or is this a problem?

From the sound of it the water pump bearing is making some crunchy noises, so I'll be changing that in the next few weeks - could this lead to the problem?

Steam after properly bleeding the system is not normal. Steam after improperly bleeding the system is common. Crunchy noises from the water pump are bad. Fix now or suffer soon.

[Ross]

It's not circulating. Water pump time now, or head gasket time later.

[jamiedo]

I thought because the rad matrix was getting hot it must have been circulating? hmmm either way, already done the head gasket and dont fancy all that mess again - I'll chuck a new water pump on, do the cambelt whilst I'm there and see what happens - thanks for the advice.

(The engine sounds tappety as well - but I figured that wasn't related...)

[Mordan]

Hi all,
Have had a look through some of the threads to do with this problem but cant find the answer...

I have a 1993 518 / e34 / M40 engine 67k miles...

Its been off the road for a while as I've been doing alot of work to get it MOT ready (I told myself 3 weeks ot begin with, its been 13 months...)

It passed its MOT, but it is overheating. Have tried bleeding the air from the system, but today realised that the water is not getting hot (or even warm) in the radiator, or in the hose going from the bottom of the rad into the water pump (front of the engine block).

The water is heating the radiator matrix, so I assume the pump is working properly...

The Temp sensor seems to be working properly, and the thermostat was replaced when I changed the cylinder head...

HELP! Any ideas would really be appreciated.

I feel for you. A similar thing happened to my m40. Now that i have some time's off, I will work on it.
Mine is overheating because, the head gasket is screwed (by the previous owner), as he drove with a failing water pump.
You changed the cylinder head you say. Did you pressure/temp test it to make sure it was alright? I will have to do that with mine.
I will have to change the water pump as well. The water pump is critical element in any overheating issue.
does your heater works? because mine does not.