P38A bleedin' coolant

kermit_rr · Jun 9, 2019

Hi looking at RAVE section 26 refill.
15 - start engine, continue filling until coolant stabilises at the cold mark.
16 - run until thermostat opens (to hose becomes warm)

Reality - top house gets warm within seconds, well before thermostat opens.
Before that happens, coolant overflows because it's got an airlock that expands rapidly but doesn't shift, even though the small pipe is not blocked and coolant returns from radiator to expansion tank

To house has to get warm before thermostat opens! Why does RAVE day otherwise? Top hose goes straight to top of engine which is circulated through the top side of the thermostat

kermit_rr · Jun 9, 2019

Hmm, threats seem to work.
I've just driven 3 miles with a steady 92c and no coolant overflow

I'll watch this space!

RangeRoller dt · Jun 9, 2019

They can be bit of a bugger for airlocks

kermit_rr · Jun 10, 2019

I figured the sustained high revs of driving would blow the air out. Seems to have paid off!! The level dropped in the expansion tank and seems sorted!!

Grrrrrr · Jun 10, 2019

kermit_rr said:
I figured the sustained high revs of driving would blow the air out. Seems to have paid off!! The level dropped in the expansion tank and seems sorted!!

Yes, I have had success with the V8 by filling the expansion tank, revving to 2000 rpm and peering through under the open bonnet and topping up as necessary.

RangeRoller dt · Jun 10, 2019

I stick to 2000rpm gently.
Gave my old beemer a good revving when air wouldn’t come out, spat it out everywhere and made the alloy work go all manky

kermit_rr · Jun 11, 2019

Just did a 30 mile round trip, stopped at the petrol station, waited for a pump and the temp started to rise. Looked under the bonnet and the pipes were rock hard with coolant dripping from the overflow!! Let it cool down and coaxed it home! Water temp started to drop again as ipulled into my street and when i checked. The level had dropped in the expansion tank!!
At no point did I hear the fan so I'm wondering either a bit more air got stuck then freed itself, or if the viscous fan isn't working properly and it just overheated? Or a bit of both!?
When i say overheat, I never let it go over 105c before shutting off so unlikely I've broken anything, the needle never moved from the middle.

RangeRoller dt · Jun 11, 2019

don’t worry they can take it a little just don’t make it a habit. Maybe left over air expanding, how old is your rad did you marble test it on the rebuild?

Fact heated when stopped then cooled running suggests VCU fan. Did you get anything up on your nanocom?

kermit_rr · Jun 11, 2019

I don't know the age of the radiator or what a marble test is, sorry!
When i had the radiator off, i filled it with hot water and scanned with an IR thermometer, seemed to have no cold spots/blockage

Don't have a nanocom yet

That purchase will be made as soon as i can justify the cost, ie run reliably

kermit_rr · Jun 11, 2019

To add, once I'd stopped and saw the temp rise, i had to stop a few times on the final mile home to let out cool. It was only in the last few yards i noticed the temp start to drop
Maybe an airlock or some other blockage that managed to clear itself?
When i was getting ready for MOT, I let it idle for a while and it never went over 93c

brianp38dse · Jun 11, 2019

The marble test is to see if the baffle in the rad top is there, with rad of pop a marble in one side tilt rad to other side if marble comes out no baffle, new rad time.

kermit_rr · Jun 11, 2019

brianp38dse said:
The marble test is to see if the baffle in the rad top is there, with rad of pop a marble in one side tilt rad to other side if marble comes out no baffle, new rad time.

I'm not sure I understand, take rad off, put a marble in the top, or the bottom, or both? Where should the marble come out from?

brianp38dse · Jun 11, 2019

Put marble in top and it should not come out the other side as the baffle in the middle of the top should stop it
the baffle makes the coolant go through to the bottom of the rad then up and out the other side, if that makes sense.

Grrrrrr · Jun 11, 2019

What's the viscous fan like? Water pump? Thermostat? Cannot remember what you've done. Yours is a v8 yes? Is there a baffle in the V8 rad?

kermit_rr · Jun 11, 2019

Makes sense, but there's no hole for it to come out of on the other side, i think I'm being a bit dim

kermit_rr · Jun 11, 2019

Grrrrrr said:
What's the viscous fan like? Water pump? Thermostat? Cannot remember what you've done. Yours is a v8 yes? Is there a baffle in the V8 rad?

When it was registering 100c the fan was easy to spin with my fingers, engine off, hence why i think it might be dead or at least failing. Waste pump looked new, metal fins not plastic
Yes it's a thor 4.0. Trying to figure out the baffle bit

Grrrrrr · Jun 11, 2019

kermit_rr said:
When it was registering 100c the fan was easy to spin with my fingers, engine off, hence why i think it might be dead or at least failing. Waste pump looked new, metal fins not plastic
Yes it's a thor 4.0. Trying to figure out the baffle bit

Baffling?

Diesel rad has a baffle to stop water flowing straight across the top of the rad. so the water goes in, down, along and then back up.

Trying to remember what the V8 does and if it has a baffle.

Does the fan roar on startup?

kermit_rr · Jun 11, 2019

Standing in front, looking at the engine, the top rad hose connects to top left of the rad, the thermostat connects to the bottom left of the rad. There are no connections on the right hand side of the rad
Edit: yes it roars on startup until it settles

Grrrrrr · Jun 11, 2019

kermit_rr said:
Standing in front, looking at the engine, the top rad hose connects to top left of the rad, the thermostat connects to the bottom left of the rad. There are no connections on the right hand side of the rad
Edit: yes it roars on startup until it settles

That sounds right.

Air-con fans should cut in to help cooling as well.

RangeRoller dt · Jun 11, 2019

kermit_rr said:
There are no connections on the right
Edit: yes it roars on startup until it settles

My mistake sounds like your rad is different. Sorry

P38A bleedin' coolant

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