320 Racer over heating- any ideas??

[JimmyC]

I was meant to be out racing last weekend, but due to over heating problems I only managed 3 quali laps and a few race laps so an expensive problem with £275 worth of lost race fees

Basically after fitting a brand new head to my car, its a bog standard 320 lump complete rebuild, was running 1/2 way on the previous head which unfortunetely was cracked from fitting. But this weekend, ok it was hot so would expect 3/4 temp, it was hitting the red forcing me to stop.

I have removed the thermostat, and put the plate back in (Iwas told that helps water flow)
The head is brand new
The water pump is 6 months old
The cooling system is pre 87, the engine a 91 car
It ran fine on the previous head

The rad is cold to touch, and the hose from the thermostat housing to the top of the rad seems to be getting air into it even after pressure bleeding the system.

anyone got any ideas, we are truely baffled???

Cheers

Jimmy

[Simon13]

is it using any water?

how old is the thermostat?

[JimmyC]

its not loosing any water at all

The thermostat has now been removed so its permantly open

I just cant get my head around it

[mrLEE30]

did you try removing plugs to see if any look to be steam cleaned?? indication of a blown head gasket.

i thought the pre 87 cooling systems were slightly different, i.e. a different bleeding system (at least it is on my 87 325 compared to my 92 320).

and if the rad is cool then seems that is the problem, so check for air in system (i know you have already but massage the pipes to get it all out, and do you have the heater matrix still in, if so is there air in that?), and could also be the water pump packed in. difficult to diagnose problem from remote, as suggested is it using water, is the radiator/expansion bottle cap the correct type?

more info please!!

mrlee

[E30BeemerLad]

as I type this it sound less & less likely/ credible, but i'll say it anyway as thse things can often be something totally daft....

have you fitted a different type water pump? Has it misbehaved since the head swap?

Have you fitted an earlier type water pump to the facelfit bottom end? The earlier pump has an extra outlet for the expension tank which is on the driver side of the car compared to the passenger side on the facelift. Not sure if all the plumbing is correct.

I have also seen the living legend that is Brianmooore say on several occasions that it is best practice to have the front of the car jacked when bleeding in order to remove all air bubbles.

Has the radiator been investigated/ poked a hose into it to check on flow?

Just some suggestions, probably no use whatsoever though
cheers
Lee

[Ant]

The cooling system is pre 87

So you have the header tank mounted on the O/S inner wing then ?

[JimmyC]

Blimey lots of knowledge coming all at once, right bear with me here ;)

The newly built engine has a block from a 1990 car, it has had a full rebuild. After the original rebuild I used a 2nd hand head which when pressure tested was fine- it was pressure tested at an ambient temp. This head after 2 trackdays was shown to have a rather large crack in it- so I binned it.

Last week a brand new (not recon) euro car parts head was fitted

So basically its a 1990 motronic engine running a pre '87 water pump and cooling system- is that a problem??

It is loosing no water at all, so head and gasket are fine.

The heater matrix is also brand new

I am pretty convinced it was not an air lock as it was bled very thoroughly.

The rad was cold so that suggests that water is not circulating correctly, the hose from the top of the rad to the thermostat seems to be holding air (maybe wrong though)- no air when cold, but after a run its seems to be collecting there??

The car has never over heated on track before- even with a cracked head it ran a steady 1/2

Its only over heated since the new head was put on.

The thermostat, is out and will stay out as I have been told by every bm racer out there that its stupid to have it, what has gone back in is the housing/plate that its held in- so effectively it is in and always open- does that make any sense??

[JimmyC]

The cooling system is pre 87

So you have the header tank mounted on the O/S inner wing then ?

yep

[Martinaston]

i'm a bit lost the thermostat explanation
sounds like you've blocked the output to the rad when the bit you want to block is the port that re-circulates the collant back into the block.

[Martinaston]

The idea of jacking the front up is just to get the air lock out of the matrix not so much the engine.

[JimmyC]

Sorry, if i'm not explaining this right

The thermostat plating is still in place to direct the water? effectively I have removed the centre of the thermostat leaving it continuously open.

Is that a bad idea??

I was stopping just prior to it getting that bad- ie just as it crept into the red- it was def getting that hot so unfortunately the gauge is right?

I can put the stat back in, but I still need to find the route of the problem

The pipe is not blocked as I checked that

How can I check the head??

And also someone mentioned that I should look at changing the header tanks lid?? whats that about??

Cheers for all your help guys

[Gt6s]

PUT THE THERMOSTAT BACK IN!!!!!!

Removing it means that the coolant only goes around the bypass circuit meaning that the rear 3 cylinders don't get any cooling at all. If you were having cooling problems before this, look at the rad. If it behaves itself at low speed but starts acting up when at speed the rad is a good place to start. Forget about back flushing it, just fit another one.

ABSOLOUTLY !!
I tried my one with stat removed would not circulate at all. Further inspection of stat revealed it was a bypass item redirects coolant flow without stat coolant will not circulate correctly.

[JimmyC]

The stat is in, just the valve removed i.e its always open

It idles nicely at 1/2 but under strain it rockets to the red, it was doing this with the complete stat in so its not that.

Been speaking to a man in the know today and he thinks i'm up the wrong tree with the head, and first place to start is the rad so a new rad will go in this week, and he'll take it for a burn on the trade plates.

[calder]

good luck Jimmy, let me know if you need any help (not that i can do much).
just to disagree slightly with some previous posters, 100mph on an autobahn will only put the load of engine/transmission frictional losses and 100mph air resistance on the engine. This will not necessarily be a massive load and hence cooling duty to hold a constant speed. Also with 100mph air velocity hitting the rad and under the engine bay cooling will be improved.
Repeated WOT acceleration from 4500 to 6000 rpm in 30°C ambient will give a higher heat load with speed varying from 30 to 90mph.

[Simon13]

u don't do 30mph at the nurburgring! it's all 3rd gear baby!

[Brian28]

As Richard has already said Jimmy, Lydden was extreme ambient temps and with our gearing for the track was fairly hard on the car all round with no straight or decent windblast (BBQ after effects excepted ) to speak of. Your car could do the 'ring trip tomorrow, 100mph autobahn and blast round laps all day no problems, but another Lydden weekend could kill it.