W126 running hot after intake work
 

Replaced intake gaskets. Not she runs dang near 115. Never more than that. I did several burping attempts, even unscrewed the sensors to free any trapped air. Still runs hot.

T-stat is newer Gates. Pump certainly works. Top of radiator gets plenty warm. Aux fans do kick in, so I don't think its a sensor issues unless two go bad at once.

Did some searching, but is there anything special I need to do? System should be self bleeding from what I understand.

I always remove top hose from radiator and fill it that way.After I fill block and rad.

+1

Been there, done that with filling upper hose at radiator. Burped this thing several times today. The temp is certainly related to engine RPM. At 70mph she gets to 115c. At 55, 105c. Slower, about 100c. Very consistent temps at these speeds. If I turn on defrost she drops 5c pretty quick then will slowly drop another 5c.

Its like she just can not cool. My first thought was AF mixture. But she is running nice and since I got rid of any air leaks (if any), she would actually be running richer.

I did cool burps, hot burps. Disconnected hoses. Pumped the upper hose so all I could fee was water in it.

It just weird, I have changed the t-stat before and never had this issue. Also I will note the viscus fan clutch (BEHR) was replaced last week. No issues before intake work with that fan so pretty sure its good. It certainly feels tighter when spinning by hand and I can certainly here the dang thing spool up.

I think I may try a t-stat swap. Other than that, the only thing I can think would be that the water pump somehow went bad during this work, but that would be one heck of a coincidence. I guess before I do that, I will pull the upper head plugs in the back and see if any air comes out.

Is it possible that anything like a parer towel or rag could have worked its way into the cooling system when you were doing all this work? It has been known to happen. Ask me how I know.

I doubt it. I am really careful about those things. But I suppose, anything must be possible until proven not the case. I sure hope not. Maybe a good dose of citrus powder would dissolve anything. I only use shop towels and the car only has distilled water in it right now anyway, so no waste of coolant if I do.

I could not wait and the engine was already warm. So I loosened the head cap things at the back. Both bleed water just fine. Did the dash temp sensor too again, same. It really seems like the coolant is flowing. Just either not fast enough (blockage as suggested) or t-stat is holding back. The upper hose gets plenty hot, top of radiator is too hot to touch. I put a gallon of washer fluid in today - well that all steamed off already (stupid heated fluid idea).

Frustrating for sure. I even thought maybe I reversed the intake gaskets! Well, not possible. Car would not even run right if I did. And the coolant passages are the same for both sides.

Well I guess I am starting to rule out air pockets and move onto blockages and flow issues.

Can you tell if you are losing any coolant? How old is the radiator cap?

Expansion cap is about a year old, original MB part. Not loosing any coolant at all.

Presuming the 560 has low speed electric fans, are they operating?

" and the car only has distilled water in it right now anyway, so no waste of coolant if I do."

I'm thinking that might have something to do with it. Your normal 50/50 mix has a different boiling point. My very limited experience with MB tells me they are very sensitive to having the exact fluids in use.

Good point.

No, that does not matter. After all, I have been running distilled water for months now due to the coolant leak at the intake gasket. If anything, the system is now under slightly higher pressure further increasing the boiling point. Not to mention, in some areas many run just water (Arizona, etc).

edit: under pressure, the boiling point of water is 125c, which is the upper limit and red zone of the gauge. Adding mix at 50/50 only increases the boiling pint 6 degrees Celsius.

No, only hight speed. Viscus fan and the aux fans kick in with AC (which I do not have) or at 110-ish Celsius. Which is what they are indeed doing. Its probably the reason I do not go into full on over-heat.

If they were not such a pain to acquire (shipping, waiting, etc) I would toss in another viscus clutch just to rule it out. Quick to change. But again, its new and BEHR, not URO crap, so I am pretty dang sure its good. Feels pretty tight when hot.

Out here in Tucson, I've always run a low coolant ratio (25%) and it works very well; but I've never run straight water. Maybe you could try getting two quarts of anti-freeze in there just to rule out the possibility that it's not the lack of coolant.

You mentioned you replaced the fan last week. Is it possible that you just didn't notice the temp running higher back then, or could the ambient temperature be higher this week?

Just a quick thought. On my 500, and I believe your 560, there is a ground wire that runs from a small bracket behind the P/S pump to the left finderwell. It is the main ground for the body. If it didn't get hooked back up or didn't make a good connection then it can cause all sorts of strange problems with the gauges and other sensors.

Paul