expl0rer

Today I figured I'd give the big old beast a radiator flush. Easy enough, just a little time consuming, right? Naaaah!!!!

I am once again convinced that Murphy has a new set of laws in the works and is quietly observing me when I am doing work on the car to pen down scenarios. What really makes it funny, for me at least, is that there are several Murphys in my neighbourhood. I need to find a way to identify The Murphy in question. Maybe in another thread.

Essentially, the spigot which is supposed to allow flow of the coolant when the knob is unwound, is not doing its job. I get a slow drip from somewhere in the area at the rate of one (yes, 1) drop per second when I unwind the knob several turns, but no fluid is willing to flow out of the spigot just under the knob. Tightening the knob stops the drip and the system holds pressure without leaks (thank god for that!!!!!). I still managed to flush (only twice, time constraints) by disconnecting the rubber hose from the plastic pipe which is running horizontally just above the radiator support. These two are the lowest ones. They are accessible and visible after the front splash guard is removed. That needs to come off anyway, at least on mine with the EORP to get to the knob/spigot (and for me to realize that the job will not be as easy as the internet suggested. Again!)

I am not entirely sure how the spigot functions, but I think I have an idea. Once the knob is loosened, I was able to pull it out a bit and equally push it in the same bit afterward. To tighten the knob I needed to push it in, if I had pulled earlier, or it would not thread in. Loosening/pulling the knob should dislodge some sort of a plug which should allow the flow of liquid from the spigot. I suspect that this is either misaligned or broken and subsequently stuck. I get clear liquid when I drain the radiator. No debris or anything floating, so I am convinced that it's not plugged by gunk. It looks like the rad has been looked after before I got the car.

I did stick a toothpick in the spigot when the knob was loosened but got only so far and whatever stopped the toothpick was not willing to move, be it inward or sideways.

At it again tomorrow when I have daylight and the fluid is cool enough to drain. I am wondering if I should remove the knob and have a look inside the rad to see how the spigot is being opened/closed. Risky, me thinks.

Murphy! What'ya say?

Accepting any and all ideas and opinions. And go!

P.S. this is what my knob looks like on the outside.

rapidoxidation

Did you open anything up high to allow air into the system (break the vacuum)?
Loosen up the upper radiator hose and twist it loose from the radiator stub.

expl0rer

I did. I opened the cap of the overflow tank first, before diving under. Thanks for the tip, though. I didn't look verh closely at the upper hose, but another one to easily disconnect is the overflow hose going into the tank. Presumably less knuckle scraping too.

DennisG01

It should drain very easily with just the overflow cap off.

I think you must have a clog in there. I wonder if that red knob is removable by unscrewing it as far as it will go, then pulling it outward and unscrewing again? I've never tried - but it obviously comes out somehow, you know? Or maybe after fully unscrewing, it just pulls/pop out under a little force?

expl0rer

I think you are right.

If the knob in my radiator is like the one in the Amazon link, I would expect that I could unscrew it and remove it by pulling and squeezing the two legs with hooks.

I see how that design works. When the cap is in place and tight, both O rings are probably used as seals to prevent leaks. Unscrew the cap, pull (optional), the whole assembly moves out, the spigot is accessible via a vertical hole between the spigot and the knob's housing. Fluid flows through the two legs with hooks, through the connecting vertical hole, into the spigot and out. The inner O ring maintains a seal (and maybe the outer one too)

So I must have a block in the connecting vertical hole, or the knob housing (less likely as I did get some drops out) or the spigot itself, but I did not feel that was the case when I poked with the toothpick. I feel more confident about removing that knob. But maybe not over the weekend. I won't be able to source new O rings if necessary till next week. Will just need to use distilled water instead of coolant - short term. And keep an eye on coolant temps.

On a separate note, my idea of how the knob/spigot worked together was not as simple as this one.

expl0rer

I took that knob off today. After several revolutions the thread is fully exposed and you oy need to apply some relatively low pulling force for it to come out.

Short version of my investigative findings: I must have the passage from the know to the spigot completely blocked.

Long version: Could not see anything blocking anything that looked remotely like a passage between the two. Even with a borescope. The space is tight, the holes aren't much help with their size and I was on the ground, not under a lift. So I left it all the same as I found it. In 10 years time when the next flush is due, I will be reminded of the plugged spigot again. Or maybe I won't have the car, or the rad will not be the same.

Max Blast

Did you try some compressed air at the spigot hole to dislodge whatever is blocking that orifice?

chassis

Agree with a bit of compressed air to dislodge blockage. Has any "Barr's Leak" or similar been used in this vehicle?

Miguk_Saram

Here's a thought:

Hypothetically, based on your description, idling the vehicle with the drain plug removed should result in no fluid leakage. That would validate your blockage theory. Perhaps you can test that.

On the other hand (bright side?), maybe doing so would dislodge any existing blockage and allow you to perform the flush.

Of course (and this goes without saying), don't be under the vehicle when you test this hypothesis. And take all necessary precautions, including a deep, wide-mouth bucket to collect any spewed/splattering hot liquids that may be discharged at the drainage point.

DennisG01

I would try getting the engine up to operating temp, then opening (be careful, of course, for spewing hot coolan) the drain screw. Maybe the pressure inside the system will loosen/blow it out. Might be a little tricky on your back, though. Make sure to keep your face out of the way. Think it through before you try, though - I'm just speaking outloud without actually being down there to see if I could inscrew it fast enough and pull my hand/arm out of the way.

You could also (first?) try removing the screw and then blasting the hole with a hose.

chassis

.

chassis

These are for 166 with M157/M278 engines. Note the extra step for M157/M278.

Not sure if this engine is used at the end of X164.

Also bear in mind that if the coolant is not fully up to operating temperature, other thermostats may not be full open, for example to control coolant to engine oil and transmission coolers. These are installed for some V8 engines, not sure which ones.

DennisG01

You could also pressurize the system (cold) with a pressure tester.

Or... use a shop vac into the drain hole - just use what you have laying around, with duct tape, to get to a small enough fitting.

EDIT: Another thought... push a zip tie into the hole - it's stiff enough to push, but still bendy.

expl0rer

I was thinking about that, but I was afraid that if I dislodged the blockage it would end up in the rad and circulate with the coolant into places it should not be.

No idea if any products had been used prior to my acquisition. I'd say no, but that's just a guess.

If I unscrewed and pulled outward or fully removed the knob, the coolant will flow freely from the knob's orifice. The trouble I had (and still do, really) was the fluid not flowing through the spigot which is directly under the knob. It only takes 5-6 full revolutions for the thread to fully disengage. Based on what I've seen online, a couple of revolutions should be sufficient for fluid to start flowing through the spigot.

Edit: The idea of pressure clearing the blockage I like, I did not think about that as an option. Lack of control over the hot liquid under pressure is making me hesitant to try it, though. The only way to stop the liquid flowing out is to screw the plug back in, but my hand will have a "meet and greet" with the hot coolant.

video reference:

screen cap from the above video:



You must be helping Murphy with the new laws write up lol I like the idea of pressure and allowing it to do its magic. I did not think about doing this, but yes, risky and I must be super careful with positioning.

Thanks for those! I had to run the temp up to 95C to be sure the thermostat was fully open, and also the AC/heat to ensure the heat core got flushed as well. I kept an eye on temp with iCarSoft MBII. The cluster does not move noticeably past the 85(ish)C mark, despite the temp scale showing 100C.

Great ideas. I might try the zip tie or make a pick out of a paper clip.

On a separate note, I took the beast on a 1000+ km trip over the weekend and she performed pleasantly well. Solid highway cruised indeed! I managed 12.9 l/100 km fuel consumption over the entire trip. Not too shabby for a 550, I think. Driving ranged from 80-110 kph zones. I usually drive 10-20 over the speed limit depending on location (populated areas vs middle of nowhere) and gave myself some freedom to 130 kph here and there. This was our first longer trip with the GL since taking her into the family. I think she qualified for the "long haul" wheels in the family.