How to flush coolant questions

[Ryan S.]

I am about to flush coolants and I found this very helpful how to guide by Dave. http://www.dmcnews.com/Techsection/cooling.htm.
And as usual, I have a few novice questions.



"To drain the system, remove the lower radiator hose connection. Careful - it’s plastic. "
Do I really have to remove the lower rad hose? I am just afraid that I might break it. Is there other safe options for this?



"Next you reconnect the heater hose to the overflow bottle and disconnect the upper radiator hose from the engine at the housing that contains the bleeder screw. (This is the larger of the two large radiator hoses)
Upper radiator hose from engine is #16 hose, right?



You then shove the garden hose down into the upper hose connection and wrap that wet towel around the connection again. Or make another PVC barb to hose fitting - 1-1/2" barb is the right size.
- So I am going to put a garden hose into #16 hose. Water flows from #16 hose to pipe #18 to radiator, right?



Turn the water on low pressure and this will force clear water through the radiator the opposite direction it is used to."
- "Opposite direction" - I always thought that coolant was traveling from thermostat to #16 hose to #18 pipe and activates otterstat switch??? Or is hot coolant travels from radiator to #18, otterstat, #16 hose then thermostat?



"When finished you then pour two fresh gallons of antifreeze (if using distilled water put it in first) into the upper radiator hose
- It is still the #16 hose, right? So the fresh coolant is going in from #16 to #18 to radiator and etc..


Thank you very much in advance for answering my questions!!
http://store.delorean.com/images/Category/large/1-3-2.gif

[DavidProehl]

Do I really have to remove the lower rad hose? I am just afraid that I might break it. Is there other safe options for this?


To drain the radiator you have to remove the hose. Newer radiators have a peacock drain valve so you don't have to remove any hoses, unfortunately the stock radiator does not have such a valve.

You might be able to flush it clean though. I imagine if you were to flush enough water through your system eventually it would come out clear without draining the radiator first, but it would take a while.



Upper radiator hose from engine is #16 hose, right?

I see where this is confusing. Connecting water to #16 would not be the reverse direction but that is definitely the hose being described. Flushing via the overflow hose listed previously in the article would be the opposite direction. I think you will get a good flush by running water through those two hoses (overflow to coolant bottle and #16).

Disclaimer: I have not done a flush on my car. I have drained it completely a few times, but never flushed with a garden hose.

[NightFlyer]

This is what I do, if it helps you any:

Instead of pulling the hoses off the radiator, I prefer to pull the hoses (9 and 16) off the pipes (5 and 18 ) in the engine bay. If you still have a stock/OEM radiator with the plastic side tanks and flanges/collars like I do, the less you pull the radiator hoses off and on, the less problems you'll have later on down the road with the radiator - at least that's my take on it. I then proceed to drain and back-flush the radiator (by using a spray nozzle on a garden hose on the opening to pipe 18, and using the nozzle with a rag wrapped around it to build up some moderate water pressure) and heater core / engine (by pushing water through the disconnected top hose of the header bottle) separately. Up to you if you want to pull the block drain plugs - sometimes I do, sometimes I don't.

If you're trying to collect the old coolant, as opposed to simply discharging it onto the ground, then you'd run compressed air through the system during the catch phase, followed by your back-flush with water. Be careful not to put too much pressure through the system, but a moderate amount is necessary to do a good job and won't hurt anything.

After the back-flush, I like to blow the system out again with compressed air, using the air to dry the water from the back-flush, as my garden hose water is quite hard and I want as little of it left in the system as possible before refilling. I refill the system only after it's completely devoid of liquid/fluid, or at least as empty as is reasonably possible.

I then put the drain plugs back in the block and reattach the hoses to their pipes, leaving only the top hose of the header bottle still disconnected. Note that I don't remove any of the hoses near the thermostat / water pump.

I then prepare my coolant mixture in a clean 5 gallon plastic bucket. 40% distilled water, 60% concentrated Prestone DexCool Antifreeze, and a bottle of Prestone Cooling System Treatment (it's a combination corrosion prohibitor and lubricant). I prefer mixing it myself as opposed to buying the premixed 50/50 stuff (no good reason for this - I just do) and always mix up about a half gallon more than I'll actually need. Yeah, I use DexCool (the orange stuff) and have been doing so successfully for the last 12 years, despite what others on the forum have said about it. DO NOT use any kind of sealant tabs or a liquid sealant product unless you want a mess and a plugged up cooling system.

I then use an old (previously flushed) fuel pump and prime it with my coolant mixture in the 5 gallon bucket. Once primed (free of air), I hook the fuel pump up to the still disconnected top hose of the header bottle, using a simple barbed coupler and a couple of hose clamps. I then activate the pump and allow the system to fill until the header bottle is practically full (don't worry about overfilling, as the system will purge whatever it doesn't want).

I then reattach the hose to the top of the header bottle and place whatever mix remains in my 5 gallon bucket into an empty antifreeze jug.

I then jack the rear of the car about 3 feet into the air and position jack stands in the regular locations. Set the HVAC mode switch to the heater or vent positions. I then start the car with the rear end in the air and allow it to get up to temperature (thermostat opening and cooling fans engaging). But always be sure to watch the temp gauge and immediately shut the engine off if you believe you're on the way to overheating. You'll want a bucket under the purge hose from the header bottle unless you're just discharging onto the ground, although the first warm up should result in most of the excess coolant in the header bottle being sucked into the system. After the fans have run for a minute or two, kill the engine. Check and top off the header bottle if needed. Repeat running the engine up to temp, stopping, and checking/topping off the header bottle until you no longer have to top off the header bottle or the header bottle starts dumping a significant amount of coolant out the purge hose and into your catch bucket / on the ground. You should only need to repeat once. Doing this with the rear end in the air purges all the air from the cooling system via the header bottle without having to mess with any of the bleed valves.

I don't run any kind of self-bleeder kit on my car - all 100% stock/OEM (with the exception of the heater control valve - original one developed a leak at the pivot).

Put the rear end back on the ground, top off the header bottle to an over filled level if necessary, and take the car for a good 10-20 minute drive, being mindful of the temperature gauge. At the end of the drive, check the header bottle and top off if needed, leaving it over-filled, but you should be done.

Note that if you don't refill with some type of purged continuous flow pump as I do, then you'll have to bleed at the waterpump/thermostat housing bleed valve/nipple. Also, if you remove the block plugs during the drain and flush, be sure to teflon tape and anti-seize the threads before re-installing.

So, that's what I do and it has worked great for me over the years. My car has always run nice and cool, as Steve can confirm (95F ambient temp in bumper-to-bumper slow moving Woodward Dream Cruise traffic for over 90 minutes and my car never breached about 180F).

As always, best of luck and have fun with your DeLorean!

[Ryan S.]

David and Josh,
Thanks for your reply. I have a few questions for Josh.


Instead of pulling the hoses off the radiator, I prefer to pull the hoses (9 and 16) off the pipes (5 and 18 ) in the engine bay.... then proceed to drain and back-flush the radiator (by using a spray nozzle on a garden hose on the opening to pipe 18, and using the nozzle with a rag wrapped around it to build up some moderate water pressure) and heater core / engine (by pushing water through the disconnected top hose of the header bottle) separately.

Just want to be clear...Are both #9 and #16 hoses disconnected while you put a garden hose through pipe 18? And also while you put a garden hose through heater core hose (top of header bottle), are both hoses disconnected?
I don't have air compressor or extra fuel pump. So can I skip that steps and just put fresh coolant through #16 hose? Is there any advantage for putting fresh coolant through 1/2 in heater core hose vs. #16 radiator hose?
I do have DMCNW Toby's self bleeder system installed - Bleeders by T'stat and upper radiator hose.

Thanks again,
Ryan

[NightFlyer]

David and Josh,
Thanks for your reply. I have a few questions for Josh.

Just want to be clear...Are both #9 and #16 hoses disconnected while you put a garden hose through pipe 18?

Oops - that should have said to put the garden hose onto pipe 5, NOT pipe 18. My bad.

Pipe 5 allows you to back-flush, whereas pipe 18 merely follows the regular flow of the coolant.

As to whether or not both 9 and 16 hoses are disconnected while back-flushing - it depends. If you pull the drain plugs on the engine, then you'd leave pipe 18 and hose 16 connected. The coolant and water will then leave the system via the engine drain plugs and hose 9.


And also while you put a garden hose through heater core hose (top of header bottle), are both hoses disconnected?

It really doesn't matter, but yes, I have them both off while back-flushing the heater core. You have to have at least one off for the coolant and water to drain from the system, unless you're draining it elsewhere in the system (engine drain plugs).


I don't have air compressor or extra fuel pump. So can I skip that steps and just put fresh coolant through #16 hose? I do have DMCNW Toby's self bleeder system installed - Bleeders by T'stat and upper radiator hose.

Using the air compressor is something I do to push most of the remaining water from the flush out of the system, so that the system is as empty as possible before refilling. If you don't have an air compressor, then I'd recommend jacking the front end up after you're done flushing while the hoses/pipes are separated to allow the flush water to drain from the radiator, pipes, and heater core. OR you could reconnect one pair of pipe/hose and use a wet/dry shop vac on the open pipe to pull a vacuum and get the remaining flush water out that way.

In all actuality, this probably isn't necessary. The only reason I like to 'dry out' the system before refilling is because my flush water isn't the best (very hard) and I like to meter out the water/coolant mixture as precise as possible (call it DeLorean OCD).

The fuel pump merely makes it so that I don't have to bleed the system at all or remove any hoses from the water pump. As you have bleeders hooked up on the thermostat housing and radiator, you can fill the system however you like just so long as you get it completely full via topping off, bleeding, topping off, bleeding, until you're full. Of course, with your bleeders, this means that you don't have to put the rear end up in the air while running it up to temp like I do, however, it would probably still benefit you to raise the rear end while filling your fresh coolant, as this would help push air from the radiator/pipes/heater core while filling.


Is there any advantage for putting fresh coolant through 1/2 in heater core hose vs. #16 radiator hose?

The only advantage is that you'll fill the system and clear the air faster. Other than the water pump, the heater core is the highest point in the system. If you fill the entire system via the heater core with a purged continuous flow device (such as my old fuel pump), you'll push all the air out of the system and into the header bottle during the refill.

Hope that helps!

Best of luck :thumbup:

[Ryan S.]

Now things make much more sense.
Thanks Josh!!! I really appreciate you taking time to explain the process.

[NightFlyer]

Now things make much more sense.
Thanks Josh!!! I really appreciate you taking time to explain the process.

Thanks for helping me catch that error - I've been posting and PM'ing that procedure for almost a year now, and no one else had caught it yet. I was able to make the correction over on Today, but only admins/mods can edit old posts here.