e30 cooling system issues after new HG

[Etwenty1 45]

Have put a new HG on a FL 325i, head skimmed, new WP, TB, thermostat, drive belts.

Problem is car over heated quickly on first start up - 3/4 on the gauge with an inital fill, unbled and was boiling in the hoses.

Have refilled and bled it several times and temp rises slowly to just over halfway on the gauge. Water then starts leaking from the cap (not the overflow) have replaced the cap with another 2nd hand one (2 bar)but it still leaks from the neck. Neck of reservoir does not appear to be cracked.

When its hot the bottom hose is still cold and so is the overflow. (new water pump fitted and belt tension is good) Top hoses are not and very firm (pressurized)

With the cap off there are no bubbles but the coolant (water at this stage) gets forced out as it warms. I figured this is normal in a pressurized system.

Car idles with a slight miss.

I'm going to pull the thermostat tomorrow to check it. After that will do compression test.

Any suggestions appreciated.

Edited May 16, 2013 by etwenty1

[Navin 180]

blocked/semi-blocked radiator?

[_ethrty-Andy_ 2122]

sounds like blocked radiator to me too. but when you say its cold, is that a large difference compared to the top hose, or just a little bit cooler? can be hard to diagnose on a forum some times

[hotwire 352]

Are you sure you bled it properly? They can be a bitch!

I normally 2/3 fill the system, (also make sure heater is on hot) open the bleed screw & run until thermostat opens. Then fill the system & recheck when cold.

Was it ok before the HG? If so - unlikely to be the radiator

[Etwenty1 45]

sounds like blocked radiator to me too. but when you say its cold, is that a large difference compared to the top hose, or just a little bit cooler? can be hard to diagnose on a forum some times

cold, not just a bit cooler.

[Etwenty1 45]

Are you sure you bled it properly? They can be a bitch!

I normally 2/3 fill the system, (also make sure heater is on hot) open the bleed screw & run until thermostat opens. Then fill the system & recheck when cold.

Was it ok before the HG? If so - unlikely to be the radiator

bought to fix with blown HG. Found fire ring on back cylinder damaged possibly from during overhaul a year prior.

or is this pressure from the opening nearby?

PO said car had coolant leak from heater core. No sign of this leak, thought i would get running then track down causes.

Followed that bleed procedure. Checked when cold and level had dropped maybe 1 inch. On extended idle overheat and leak from cap occurs.

Edited May 2, 2013 by etwenty1

[zl2cq 1]

Can the HG go on a wrong way or be the wrong one - partially covering a water way .....

Front raised, motor running, cap off, heater on, keep topping resivour, check bleeder, run till hot. Leave cap off.

Turn off - check & top up resivour when cold, run motor as normal but recheck resivour only when cold.

[Etwenty1 45]

Can the HG go on a wrong way or be the wrong one - partially covering a water way .....

Front raised, motor running, cap off, heater on, keep topping resivour, check bleeder, run till hot. Leave cap off.

did that, coolant started flowing smoothly out of the reservior until it boiled.

HG can only go on one way.

Edited May 2, 2013 by etwenty1

[Etwenty1 45]

Are you sure you bled it properly? They can be a bitch!

I normally 2/3 fill the system, (also make sure heater is on hot) open the bleed screw & run until thermostat opens. Then fill the system & recheck when cold.

Was it ok before the HG? If so - unlikely to be the radiator

Manually checked thermostat and it opens fine, drilled hole and ran hose thru rafiator and all hoses.

Checked viscous fan cltch with rolled up paper and fan stops easily regardless of temp. Bottom hose stays cold so not sure if viscous bit is getting warm enough to change. If the fan is controlled by a viscous thing that is directly temp sensitive, what is the 3 prong sensor on the rad for?

[e30ftw 394]

Have you changed Waterpump when you did HG? Maybe your water pump is stuffed and not pumping through water?

Does the bottom hose connect to Waterpump? Can't even remember lol. Just an idea..

[Etwenty1 45]

Have you changed Waterpump when you did HG? Maybe your water pump is stuffed and not pumping through water?

Does the bottom hose connect to Waterpump? Can't even remember lol. Just an idea..

Good suggestion but new waterpump.

[euroriffic 595]

I had a similar problem with a gt starlet once... Was a blocked heater core and a rooted radiator. Even tho water flows through the rad doesn't mean that it's working right. I'd be taking it out and getting it tested. And check the heater isn't blocked while the rads out. Mine was and all rusty so forced coke into it and it cleaned it out nicely

[Etwenty1 45]

Have done a compression test (twice now) WOT all cylinders are 185-190 after 5 or 6 revs.

I was cheered up by that but car has a miss at idle and is still puffing condenation out the exhaust. This might disappear after a long run ?

Will now be taking radiator to the shop to be tested.

Have also been trying to test the viscous fan clutch. It appears defective as in easily stooped by newspaper even when temp is showing hot - because the lower rad hose is cold i am unsure whether the clutch is getting warm enough to stiffen.

[Etwenty1 45]

So I decided that the radiator looked old and crappy and i was happy to replace so fitted new one today hoping that would resolve. Slowly filled until coolant leaked from bleed screw then ran until warm. so i see the coolant level creeping up very slowly until it starts to spill over, that's trapped air heating up i think so, bleed, rev, bleed rev, open screw etc after each rev there is 4-5 tiny bubbles escaping from the thin line from the rad.

Then the thermostat opens and there is a drop in coolant and its surging up and down in the tank but not spilling over (cap is off) the top hose is warm not hot, level become stable and i think great, put the cap on, hop in but then i hear water boiling in the heater area and temp is climbing over 1/2 way. i look under the car and coolant is dripping from a drain hole in the floor pan on passenger side. I can hear it sloshing out of the heater but can't see a leak from any of the heater pipe junctions...?

Have removed heater core and valve for pressure testing............

Still hopeful that head and block are ok and that this is just a cooling system leak - its ok till i put the cap on then pressure builds and its blowing out in the heater somewhere.

[*Glenn* 854]

Are you sure it's the correct thermostat for your engine ? the thermostat has a direct bearing on water flow as it is double acting. We have also had problems with non genuine thermostats in the past.

[Etwenty1 45]

Are you sure it's the correct thermostat for your engine ? the thermostat has a direct bearing on water flow as it is double acting. We have also had problems with non genuine thermostats in the past.

Used this one Thermostat Its is listed as compatible with oem 11531713040 I tested it in a pot of water to see it opened but will get a genuine unit if you reckon it will make a diff. Cheers

Edited May 16, 2013 by etwenty1

[*Glenn* 854]

The one pictured should do the trick if it's working correctly