80c New Radiator, New Pump, no Thermostat - PeachParts Mercedes-Benz Forum

Assault · #1 05-17-2015, 05:58 PM

Hello,

That is right folks, having replaced the radiator (brand new core), replaced the water pump, lower radiator hose, as well as the coolant (lifted the car to point where the tail pipe was close to touching the ground while refilling coolant) the car would climb over 100c going over 60mph on level ground.

The car has overheated twice to my knowledge as the previous owner replaced the head gasket because coolant poured out the servo, and once under my ownership. My best guess is a head gasket or the block it self is fractured causing the above problem.

Now here is the part where I am baffled I took the thermostat out (after trying 2 new ones of different brands) and the car runs between 82-79c which is what it ran at when I bought the car. To my understand the car should run around 60-40c without a thermostat.

I have not replaced the temp sensors above the thermostat, nor have I done a compression check yet. The valve cover and injector washer just arrived all yesterday. What is going on? Should I be looking for a new car (if the block is cracked I have no intention of rebuilding the engine)?

Thank you!

leathermang · #2 05-17-2015, 06:07 PM

Quote:

Originally Posted by Assault

Hello,......
To my understand the car should run around 60-40c without a thermostat......

Where did you get that impression ?

tjts1 · #3 05-17-2015, 06:20 PM

Your thermostat is more than just simple shut off valve for coolant flow to the radiator.

leathermang · #4 05-17-2015, 06:35 PM

" it is therefor wrong to remove the thermostat for better cooling of the engine "
from the FSM picture posted..
I was going to get to that .... but always interesting to see where bad info originated from... particularly with him citing such specific temperature range...

Assault · #5 05-17-2015, 08:20 PM

Perhaps I should better clarify my understanding.

They way I am looking at it is when I removed the thermostat I should exhibit similar symptoms of a thermostat that is stuck open. Which various people on the internet have reported they car would run in the 60c range.

However, I have removed the thermostat entirely from my car *I understand that a thermostat has a specific purpose and it SHOULD be in the car* and for reasons unknown to me the car is displaying 80c on the tempurature gauge inside the car. Now I understand that this should not be the case, and I am baffled as to why this would be the case.

Should I be looking at doing a compression test, after a valve adjustment? Would that tell me if it is head gasket or block related? Or is there something I am missing?

Thank you!!

leathermang · #6 05-17-2015, 08:31 PM

Why not the upper radiator hose ?
If it is those things you are thinking of... then some other tests ..like ' a sniffer' used on the coolant to see if leakage of exhaust gas is in the coolant... will show that...
So your electric fans are working fine..
and your viscous clutch working fine on the engine fan ?
and your servo is working fine ?

It never hurts to do a valve adjustment.... but that being out of specs is not a usual cause of overheating.... and I assume you have set them at least once since you acquired the car ?

A fractured block or head or gasket.... in and of themselves would not cause overheating... it would be if they allowed coolant to escape... or something like that.... and you would see coolant missing from the system or on the ground if that were the case.... it can escape and not be on the ground if it is going into the exhaust .. but it would still show up as missing....

leathermang · #7 05-17-2015, 08:52 PM

Quote:

Originally Posted by Assault

.....Which various people on the internet have reported they car would run in the 60c range. .....

Those people are not driving cars made by OCD German Engineers....

vstech · #8 05-17-2015, 08:58 PM

My impression is that when the 617 turbo exhibits overheating symptoms and radiator nor water pump and thermostat solve the problem, as long as the coolant passages in the block are not clogged, the head is cracked, and exhaust is boiling the coolant in the temp passage causing an increased engine temp.

Keep in mind the temp sensor is electronic, and a bad ground will cause a high temp reading also.

Junkman · #9 05-17-2015, 10:37 PM

Does a IR thermometer match the gauge temp when you measure near the temp sending unit? How hot does it get with the thermostat installed and the air bled out of the system?

Maxbumpo · #10 05-18-2015, 10:45 AM

I'd recommend start simple/cheap, and work toward complex/expensive.

When the engine appears to be overheating, can you observe bubbles in the expansion tank or out of the top of the radiator? Have to start with cap removed on a cold engine to avoid danger of burns from hot coolant erupting when the cap is removed.

Get a new thermostat, test it in a pan of water on the stovetop with a decent thermometer and a calipers. It should start to open ~80 deg c, and be fully open (8mm of stroke) by 92 deg c (numbers from foggy memory, check those in the service manual or technical data book).

When you replace the t-stat, make sure you get the orientation correct (bleed hole up) and also inspect the t-stat housing to make sure it is not eroded away so the t-stat cannot properly seal either closed or open.

If the symptoms persist, get a IR non-contact type thermometer, and measure the temperature where the temp. sender is located on the head just before the coolant leaves the head into the top radiator hose. If your instrument panel temp. gauge is accurate, then move on to things like changing out the radiator or expansion tank cap, testing the mechanical cooling fan, pull/inspect the water pump to make sure the impeller blades are cast and not stamped (cheap stamped blades just don't move enough coolant), and that the water pump house is not eroded.

Remove the radiator and have it flow-tested and pressure-checked at a radiator shop.

Take the car to an expert for diagnoses. As mentioned, there are test kits to detect diesel exhaust fumes in the coolant.

leathermang · #11 05-18-2015, 04:52 PM

In the first sentence he said he had replaced the radiator and water pump.... and other stuff.... that is why this is frustrating....

Left Coast · #12 05-18-2015, 09:55 PM

Reaching slightly over 100c is not overheating. Previous overheating episode is a flag, but plenty of engines survive overheating events. The curious part is that you couldn't get over 80c running without a thermostat. Hard to believe that happened if the head or head gasket is bad. As the graphics show, the absence of the thermostat ensures that most of the coolant bypasses the radiator, which should result in much higher running temps.

Verify the temp gauge readings. Then pressure test the system. One or more of the recently made hose connections might be leaking. The pressure cap might be failing. Look for the smaller things first. Test the two new thermostats that you already have. You don't name their brands, but they might not be the right ones for the application.

My experience with the 617 is very limited, but I do know that it sometimes takes a lot of patience to get trapped air purged out of the cooling system...and it will run hot until you do.

Quote:

Originally Posted by Assault

Hello,

That is right folks, having replaced the radiator (brand new core), replaced the water pump, lower radiator hose, as well as the coolant (lifted the car to point where the tail pipe was close to touching the ground while refilling coolant) the car would climb over 100c going over 60mph on level ground.

The car has overheated twice to my knowledge as the previous owner replaced the head gasket because coolant poured out the servo, and once under my ownership. My best guess is a head gasket or the block it self is fractured causing the above problem.

Now here is the part where I am baffled I took the thermostat out (after trying 2 new ones of different brands) and the car runs between 82-79c which is what it ran at when I bought the car. To my understand the car should run around 60-40c without a thermostat.

I have not replaced the temp sensors above the thermostat, nor have I done a compression check yet. The valve cover and injector washer just arrived all yesterday. What is going on? Should I be looking for a new car (if the block is cracked I have no intention of rebuilding the engine)?

Thank you!

Assault · #13 05-18-2015, 10:26 PM

tjts1- thank you for the diagrams they helped me determine if my thermostat was in the correct position and it was.

Vstech- Thank you for remind me to check if i might have a bad ground on the main cable. After inspecting, the copper is turning green at the part that connects to the chassis, and the bolt and nut both have rust on them. I will be replacing the cable as well as the nut and bolt and polishing the surface free of rust. Can I use por15 even paint just to seal it from future rust? Or leave it bare?

Junkman- I do not have an IR scanner I see there is a very good one on Amazon for only $20 I was unaware that they were so inexpensive! Probably would have bought one a long time ago had I bothered to check.

Maxbumpo- There is some steam that exist the expansion tank once I release the pressure (I have one of the new style radiator caps that allow you to vent the pressure before you open it). I have did the thermostat test and all three thermostats opened up the same amount. I did not have a thermometer on hand to check the temperature though. The water pump is a high quality German Hepu. Radiator is record.

leathermang- Thank you showing me the need to clarify my first post. After re reading it there were certainly some pertinent details I left out. I opted not to replace the upper radiator hose because the pressure inside the hose is pushing the hose outward preventing it from collapsing in on it self, unlike the lower radiator hose which is under vacuum from the water pump pulling the water from the bottom of the radiator. I Have yet to do a leak test, I only recently because aware that they have something like that and I will be looking into it. Electric fan is inoperable If I plug it in it will drain my battery (brand new), learned from experience. The viscous clutch is working as it should accoring to the post I have read. There is very little rotatation when i spin the fan by hand clockwise. I have no idea if my servo is working as I have no heat in the cabin. It may be related to the blower amp I have just acquired all the supplies to do a valve adjustment and will be completing it this weekend as well as a compression test.

Thank you everyone for your input, it has been enlightening reading stuff to check for, I have anew found respect for a service manual.

After following everyone suggestions here is an update. I drove the car around today maybe 25-30miles without a thermostat in, and the coolant at the proper levels. I noticed the temp gauge was sitting comfortably below 80c around 60-70c. I thought to myself well that is strange. I was able to do 70mph and the temp gauge climbed to the 70c range. Upon arriving home I drained the radiator and to my surprise the coolant was the color of a desert sunset, defiantly not the color I would want it to be. So I wounder If there was just a heavy amount of rust build up somewhere in the coolant system; perhaps the block, and running without a thermostat was able to help clean it out maybe? And or perhaps there was air in the system and running without a thermostat allowed the air the escape the system?

I installed the new wahle thermostat that I had sitting in my trunk an 80c. Refiled the system purged air etc, went for a test drive and now magically the car generally stays under 100c it hovers around 90-92c(to my understanding that is what these new 80c thermostats operate at) unless I'm climbing a hill going over 55mph then it will climb to 110c which is concerning, but in under a minute or two it drops just below 100c to around 98c. I will know more tomorrow when I drive to work, and I will be watching the coolant to see whats going on with it.

Thank you again to everyone who has provided input, it might be worthwhile to get the IR scanner after all, as Well as that leak test.

Thermostats were the following: Original MB OEM 1980, Wahle, stant

leathermang · #14 05-19-2015, 08:59 AM

It has been talked about in the past that these engines and temperature monitors SHOW working conditions FAST... as you noted..... a pretty normal hill can often be seen in the temperature gauge .... not something most are used to with other cars..as long as it goes back down everything is fine..

Now.... something I have mentioned in the past...
In the old days... when an engine was rebuilt it would be taken APART.... totally ... and taken to and immersed in a Caustic Tank .... called ' Vatting '....

On our old cars you often see rebuilds of the main friction items and the head... but Almost Never hear about Vatting...

Vatting has the potential for addressing long term buildup of sludge and Rust which , due to very straight forward physics , drops out of the coolant flow at the slowest moving part of the trip around the cooling system..... that is the lower back side ....

So over DECADES , even with a ' total rebuild' this can be left to build up and finally reaches a critical stage which accents compromised other parts. A little dirt and a few fins bent on the radiator... or the condensor in front of the radiator, fan not upgraded to the latest efficient model , radiator cap spring old enough it is not holding specified pressure.....
and then someone corrects all of these things..... and STILL has a marginal cooling system... and it is very frustrating because this condition should not exist if old school rules were being followed.... or even if from the start of the vehicle's life good flushing and replacement of correct coolant were followed.... but most of us are not the original owners... so not to blame there thankfully... lol

so here is what you might do ...
get the IR temp gauge and check the block at many places ... see if that lower rear is of a different temperature ... it might be lower in temp on the outside ... don't let that fool you just in case...
take out the core plugs.... sometimes called ' freeze plugs'.... and mechanically aggravate the bottom of the coolant cavity... while flushing and pulling out anything stirred up ... perhaps with a shop vac....
This is not an easy place to get to... and effectively stir up that possibly very hard build up of crud ...... but I know no other way except Hot Vatting.... yikes...
There might be cheap spring based cables similar to drain line rooting equipment... if that were cut into lengths and run by a drill ... ?????
Patience would be of particular benefit with this job...

Maxbumpo · #15 05-19-2015, 11:08 AM

Quote:

Originally Posted by Assault

The water pump is a high quality German Hepu.

Was the impeller stamped or cast? Stamped impellers do not move enough coolant, can result in exactly what you are observing.

I totally agree with leathermang's recommendation on a very thorough flush. I don't know if a citric acid flush would help or not, see service manual for procedure.

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