Car overheating - air lock or water pump?

[WorldClassAccident]

I have replaced the air intake and the engine runs. Hooray.

A quick test run showed everything was good. After about ten minutes driving I decided to head over to my favourite private stretch of road. As I was driving there I noticed the thermostat was starting to rise. It was quickly approaching the red and coasting down a hill didn't seem to stop it.

I pulled over and left it to cool before driving slowly home. The temperature rose quickly even when just pootlng home.

Sat on the drive just ticking over the fan is on and the temp sits about right in the middle of the gauge. If I turn the interior heater on full thee is no warm air blown through.

If there is some kind of air lock, is there an easy way to clear it?
Any way to tell if the pump has definitely failed!

[WorldClassAccident]

The only fiddling with the cooling system I did when changing the intake was disconnecting two hoses from the old throttle and reconnecting them to the new one.

This resulted in some of the coolant leaking out. Air might have got into the system at this point.

When I topped it back up I slightly overfilled it as I did not see the max level on the reservoir. Would too much coolant kill the pump? There are no apparent leaks.

[landmannnn]

If your heater isn't getting hot it is a dead cert that you have an airlock. Even if your water pump is broken hot water will circulate by convection so that is unlikely to be the cause.

[WorldClassAccident]

That is what I was hoping someone would say.

I knew no hot air was relevant even though I didn't know why. ��

Now, how to free the airlock???

[IanA]

On the basis that air rises- when the engine has cooled down; find the highest pipe clip in the system and loosen it to see if air leaks out before coolant.

And- check out this link and others which show the location(s) of the bleed screw(s)

[y cymro]

Nick, I hope you're recovering well.

I agree with landsman and would bleed the cooling system before looking to blame something unrelated.

Here's some bleeding advice:
http://www.carsdirect.com/car-repair...ntenance-guide

Of interest, early M52 motors, which I think you have (and the earlier M50) had water pumps with plastic impellers which are known to break up or spin on the shaft. However, as you've disconnected the heater circuit I'd look there first before worrying about the pump.

The following is copied from Bavarian Autos website - they sell a pump with a steel impeller:
"The earlier versions of these engine families (M50 & M52) were produced with water pumps that had “plastic” (actually, various types of resin and plastic compounds) impellers. These impellers have a history of cracking at the shaft hub and slipping, or actually breaking apart and disintegrating. Either way, you would end up with a water pump that looks fine on the outside (no leakage and no shaft play), but will not move coolant through the engine and the radiator. Symptoms for a cracked and slipping hub would be that the engine may run at an appropriate temperature at idle speeds or slow driving speeds, but will overheat if driven faster (higher engine speed and more heat produced). Symptoms for a broken apart impeller would be that the engine temperature just continues to climb, no matter what the engine speed is …. just as if the drive belt were off of the water pump and the pump was not turning."

I think the important symptom for you is a cold heater which usually points to an airlock or low coolant level.

Looking forward to your performance testing when this is sorted :-)

[casamolino]

Good evening pretty sure Nick is the last person in the world that needs this
(Here's some bleeding advice:http://www.carsdirect.com/car-repair...ntenance-guide), Geoff.

[WorldClassAccident]

Thanks for all the advice. I will try bleeding the system when I get time during the week.

It struck me as strange that the overheat only started happening after a fair time of driving.

Perhaps some air got forced round to form a lock. I had it on full throttle for a fair period during the prior test drive without heating issues. It was as if something 'let go' which is why I considered the after pump. Although it is a 99 registration it is a 97 build so unless the pump has been replaced it might have given up.

On the bright side, the first tests suggest performance has improved, of at least not deteriorated

[y cymro]

Everything I've read about this manifold change suggests gains of around 20bhp whereas the gains for the later M52TU are much smaller.

I've been trying some 102 octane fuel recently and that was very disappointing on a normally aspirated motor.

[WorldClassAccident]

I will do a comparative fuels video when I get the chance to run a couple of tanks of each back to back. First tank to flush the system and re-calibrate the engine monitors, the second to get the timings.

I might also try a couple of 10 tank runs to see if economy etc is affected. Not sure how to measure that accurately until I get the back light working on the mileage display. I have no way at present of knowing the mileage between fill ups.

[y cymro]

Don't waste your time and money. Performance benefits on my Z3 are only at low revs/WOT and not worth the cost in a road car. And that was running 102RON, not the usual 99.

[WorldClassAccident]

Thanks - I did try it in the Merc for a while but didn't see any great difference and never bothered to accurately measure if there was an improvement

[WorldClassAccident]

I think I am going to drain and flush the coolant.

There is an air lock somewhere and the fluid in there looks pretty filthy so could probably do with replacing.

Let's see how this goes.

[landmannnn]

Originally Posted by WorldClassAccident

I think I am going to drain and flush the coolant.

There is an air lock somewhere and the fluid in there looks pretty filthy so could probably do with replacing.

Let's see how this goes.

Don't forget the weird world of bmw coolant.

[zagmad]

My donor had its problems. Overheated, clutch seal went.water pump went so that was replaced along with the thermostat while the front of the engine was being worked on I had the belts replaced. That's why I'm popping up when I can to assist Chris with rear end.

[Scottie22]

Similar things happened to my every-day car Nick, and it turned out the head gasket had gone on that car too.

Does the header tank push water out or bubble?

[WorldClassAccident]

Car on ramp to keep it basically level on a sloping drive



Some antifreeze and distilled water to refresh - ~This new OAT stuff is red/orange which looks a bit rusty even when you put it in.



You have to drain the radiator and the engine block. Here is the radiator plug (blue) designed to pour over the air con hoses


Not much came out of the radiator


Then the engine drain up behind the exhaust down tubes.


More fluid but still looking brown and shitty



Two flushes with tap water seemed to give clear water out so then refilled with antifreeze and distilled water. Car stays cool and heater works.

Will check again in the morning.

[Roadster]

Good work Nick
Are you fully recovered?

[WorldClassAccident]

Hi - Still on crutches with a cast on. Makes working on the car really awkward.

Also driving with just the left foot makes the back ache on long journeys but at least the leg pain has gone and I am clean of pain killers.

[IanA]

That's good news.
Have you turbocharged the killer buggy yet?