Rad drain vs full drain

[BristolE30]

Hey guys,

Opinions please. Would you say a radiator flush is a sufficient coolant renewal (every 2yr) or does an engine block flush need to be done?

Cheers

[Brianmoooore]

The usual way is to drain the radiator and flush the block with a hose, so that the engine ends up full of clean water. The stuff you are flushing out is poisonous, so try to catch it, and flush away any that gets onto the ground. Take off the lower heater hose at the bulkhead, and connect a garden hose to the stub pipe. Do NOT force water through the heater from the top stub pipe.
The M20 has a block drain plug, hidden away under #6 exhaust port, if you do want to drain it. It's a 19mm hex. nut, for which I have a combination spanner, specially straightened at the ring end, since there isn't space for the normal angled end. You will lose skin from your knuckles.

[Cloggy Saint]

[reggid]

yeah it'll be fine unless it looks like dirty then it needs a proper one. when i do the water pump i do a full replacement with the BTB headers you cant access the plug

[BristolE30]

The usual way is to drain the radiator and flush the block with a hose, so that the engine ends up full of clean water. The stuff you are flushing out is poisonous, so try to catch it, and flush away any that gets onto the ground. Take off the lower heater hose at the bulkhead, and connect a garden hose to the stub pipe. Do NOT force water through the heater from the top stub pipe.
The M20 has a block drain plug, hidden away under #6 exhaust port, if you do want to drain it. It's a 19mm hex. nut, for which I have a combination spanner, specially straightened at the ring end, since there isn't space for the normal angled end. You will lose skin from your knuckles.

Thanks Brian. So your saying connecting the garden hose to the lower heater stub pipe will flush the engine block? Where will the water come out, the radiator drain hole?

Then I’m guessing it’s heater on full, bleed valve open until all air is gone from system?

Cheers
Jo

[BristolE30]

yeah it'll be fine unless it looks like dirty then it needs a proper one. when i do the water pump i do a full replacement with the BTB headers you cant access the plug

Will take a look at the quality. Always wanted one of those coolant tester things

[Brianmoooore]

The water will go through the heater matrix, into the back of the head, then down into the block and out the front. Some of the flushed coolant will come out of the rad. drain and some will come out of the hose you've disconnected.
Refill the system slowly and carefully with the car level or facing uphill. Put in the amount of neat coolant required for the complete system at the concentration you choose, then top up with plain water. Any topping up required after running the engine should be done with coolant/water mix.

[steve_k]

blood.jpg

there always is when you do any work on an e30

[BristolE30]

blood.jpg

there always is when you do any work on an e30

Truth

[BristolE30]

The water will go through the heater matrix, into the back of the head, then down into the block and out the front. Some of the flushed coolant will come out of the rad. drain and some will come out of the hose you've disconnected.

Could I plug the heater hose pipe I've disconnect to make the flushed water only come out of radiator drain? Otherwise I imagine it'll go all over the fusebox, brake boost etc

[Brianmoooore]

i'd just push it down, so that it drains under the car, but it won't make much difference if it's blocked.

[BristolE30]

i'd just push it down, so that it drains under the car, but it won't make much difference if it's blocked.

Does the ignition need to be on for the heater core to be open? Whilst I’m flushing

[BristolE30]

i'd just push it down, so that it drains under the car, but it won't make much difference if it's blocked.

And should I set to hot whilst I’m flushing it from the lower stub

[Brianmoooore]

No and no. The default of the valve is open, so with the ignition off, and hence no power to it, the valve will be open, whatever the position of the heater controls.

[BristolE30]

No and no. The default of the valve is open, so with the ignition off, and hence no power to it, the valve will be open, whatever the position of the heater controls.

Good to know. The flush and bleeding went fairly well today - there was a scary moment where no hot air was coming out of the heater for a few minutes but I disconnected the heater stub pipes for a second and it’s started pumping hot out. Do you think there’s a chance during those few minutes the head could of cracked?

On a side note after doing the coolant flush it seems my idle has returned to the low (550rpm) hunting, although I’m sure it’s not related. Just strange timing. Probably an intake leak I nudged or something

[BristolE30]

I know it is unlikely, and I’m yet to do another smoke test, but it does seem odd to me that after doing the coolant change, at the same time the idle returned to its low boggy hunting.

Is there anyway the systems are connected? Has anyone experienced cooling system and intake leaks effecting each other?

I will do another smoke test tomorrow

[BristolE30]

Smoke tests showed some cracks on the rubber intake elbow that weren’t previously there. Ordered a new one. I did glue up the cracks temporarily but it didn’t effect idle at all.

I find it so mind boggling that removing my throttle body 4 weeks ago and resetting the TPS magically fixed my idle to 750, only to do a coolant change and then it drop to it’s annoying hunting 550 idle again. And bearing in mind I barley removed the throttle body, just took it off the intake to adjust TPS. I’m not convinced it’s the cracks in the elbow as previous intake leaks have resulted in a higher idle. it’s something strange... Quest goes on

[clivej]

Good to know. The flush and bleeding went fairly well today - there was a scary moment where no hot air was coming out of the heater for a few minutes but I disconnected the heater stub pipes for a second and it’s started pumping hot out. Do you think there’s a chance during those few minutes the head could of cracked?

On a side note after doing the coolant flush it seems my idle has returned to the low (550rpm) hunting, although I’m sure it’s not related. Just strange timing. Probably an intake leak I nudged or something

I'm going to attempt to flush the coolant using this method. I have a couple of questions though:
- How do you drain out all the tap water after flushing the system (I assume you have the hose used for flushing attached to a tap)?
- When refilling the system with fresh coolant do you do this via the expansion tank or are you pushing it through the heater stub pipe?

Thanks

[BristolE30]

Good to know. The flush and bleeding went fairly well today - there was a scary moment where no hot air was coming out of the heater for a few minutes but I disconnected the heater stub pipes for a second and it’s started pumping hot out. Do you think there’s a chance during those few minutes the head could of cracked?

On a side note after doing the coolant flush it seems my idle has returned to the low (550rpm) hunting, although I’m sure it’s not related. Just strange timing. Probably an intake leak I nudged or something

I'm going to attempt to flush the coolant using this method. I have a couple of questions though:
- How do you drain out all the tap water after flushing the system (I assume you have the hose used for flushing attached to a tap)?
- When refilling the system with fresh coolant do you do this via the expansion tank or are you pushing it through the heater stub pipe?

Thanks

You don’t drain it out after, you accept a small amount remains in system. No harm. Fill from expansion tank. You only crack the stub hose to break the airlock

[DanThe]

If you are flushing after repairing the system then best to run the engine with just water to make sure there are no leaks before you put the antifreeze in