300d New thermostat, water pump = cold radiator and overheating - Page 3 - PeachParts Mercedes-Benz Forum

louis4052 · #31 05-26-2010, 03:11 PM

I would also check the radiator for debris in the fins. My 85 300TD has been running hot (up around 100 deg.) with similar symptoms. My radiator was cold in the center and hot at the edges. I took the radiator out and power washed it, blowing the fins out back to front until it drained clear. A new genuine T-stat and my temps are now steady just above the 80 mark and my radiator is hot all over.

disbo100 · #32 06-07-2010, 04:54 PM

Soft Red,

What is the latest? I have the EXACT same issue with my 98 W210. It has a new RAD, and OEM T-Stat.

It is really strange... Up to 60MPH it sits around 90C... When I go over 70 it will hover around 100 and shake a bit then shoot up to 120.

Sometimes it comes back down.. sometimes not.

Rad is warm/hot, hoses are hot and firm...

I went to the stealership and got a temp sensor since it seems to be all over the place.

If that doesnt work Im pulling all the hoses off, pull out the water pump and take a look..

Then flush the block..

After that I may resort to your solution.. rag with gas haning out of the tank and a match.. JUST KIDDING... LOVE the car..

This is just a new "ISSUE" I havent had to deal with yet and frustrating..

Im hoping its the sensor since I have NO indications the car is really running that hot.

keep us posted and Ill do the same.

winmutt · #33 06-07-2010, 05:07 PM

Quote:

Originally Posted by disbo100

It is really strange... Up to 60MPH it sits around 90C... When I go over 70 it will hover around 100 and shake a bit then shoot up to 120.

On the W123 90C is where it opens to the radiator and shuts off the bypass. Probably the same/similar for your engine?

softredvelour · #34 06-08-2010, 08:04 AM

Not much of an update, I haven't gotten the car back together yet. I'm just waiting on the housing gasket. My efforts at cutting my own out of gasket material with a pair of kid's scissors haven't turned out too well.

One thing worth mentioning: when the water pump was last installed, the gasket was "sealed" with that translucent blue silicone crap that people love to use. An excess was squeezed out into the cavity of the pump housing and may or may not have caused problems. I cleaned up the area, degreased the passenger side of the engine (just because), flushed out the block (without anything really getting flushed out), and am going to put it all back together (correctly) and hope for the best.

mplafleur · #35 06-08-2010, 09:02 AM

If the hose is cold then you have no flow and should look elsewhere, not the radiator. That should flow some, as you have done the hose in the radiator test.

Although I think now you are having some flow as from some of your latest posts. Your radiator was warm all over and temps were around 80 around town - light driving.

I had tried flushing my system after having some high temp problems. I was fine around town for a while, but rising under load. I tried thermostats to no avail. I finally took the radiator to a radiator shop and they flushed it out. They had to boil it and backflush it three times before it came out clean. It cost me less than $60 and the car has never run better. The temp is always within 1 needle width of 80* summer or winter, AC on or not.

Junkman · #36 06-08-2010, 10:44 AM

Quote:

Originally Posted by softredvelour

Not much of an update, I haven't gotten the car back together yet. I'm just waiting on the housing gasket. My efforts at cutting my own out of gasket material with a pair of kid's scissors haven't turned out too well.

I haven't seen your gasket however, if it is made from a sheet of regular gasket material: Use a ball peen hammer to make the gasket. Simply lay the gasket material on the housing and tap the material with the ball side until the housing comes through. Much quicker than waiting on the pre-made gasket.

softredvelour · #37 06-19-2010, 03:06 PM

Just a quick update:

Everything is back in and re-installed. Same problem, still overheating on the highway. I took the radiator to a shop that specializes in radiator repair and he ran a flow rate test. According to his test it only flows 10 gpm vs. the 39 gpm which it should according to it's dimensions. Case closed, the radiator is clogged. So it turns out that crouching in my driveway flushing with a garden hose is not the best way to test your radiator. Go figure.

softredvelour · #38 07-28-2010, 06:40 PM

So I just installed a brand new radiator and took it for a drive. SAME EXACT PROBLEM. top and bottom hoses are hot and slightly firm. The radiator is warm on the extreme ends and cold in the middle. How is it possible to have no flow with a new radiator, water pump, and no thermostat?

winmutt · #39 07-28-2010, 07:03 PM

With no thermostat the bypass is open.

softredvelour · #40 07-28-2010, 07:07 PM

Can you please explain some more for a merc newbie? How does the bypass work?

winmutt · #41 07-28-2010, 07:10 PM

The bypass circulates the water out of the engine and right back in. This is before you get to the radiator. While some warm water will push out to the radiator it is entirely possible that the outlet of the radiator is cool. I still think its a bad tstat.

85chedeng300D · #42 07-28-2010, 07:37 PM

Your symptoms indicate that there is not enough coolant inside the block to open up the thermostat. I had the same exact problem years ago and some cars are just too stubborn to burp, and my car is one of them, but it's an '85 with a 617. I'm not familiar with an '87 but filling the system at the heater hose closest to the firewall with the car's nose up did the trick for me after several attempts.
Good luck!

softredvelour · #43 07-28-2010, 09:27 PM

I'm going to give it a try. Thanks

kerry · #44 07-28-2010, 10:02 PM

Put the thermostat back in and burp it.

psaboic · #45 07-28-2010, 11:50 PM

I tend to agree. I think you have an air bubble somewhere in the system preventing proper flow (most likely in the block I'm thinking) put a NEW thermostat in and try burping it.