My 88 560SL is running hot. I just had the engine rebuilt, the radiator rebuilt, and a new water pump put on. The shop claims to have put a new thermostat in. The auxillary fan is working. I am not sure what to do now. I guess the thermostat could be sticking. I have re-filled the radiator reservoir with the heater on. What am I missing??

Thanks for your help.

 

560SL Newbie,

The 117 engine has a tendency to run on the warm side and this would be considered 'normal'. When you say 'hot' where is the temp needle? Also, you said you re-filled the expansion tank (reservoir).....why, had the water/coolant been under filled? Leaked? When the car is in motion, does the temp come down or continue to stay 'hot'? Did you pressure test the cap on the expansion tank?

Re the thermostat; it certainly could be sticking or installed incorrectly or not be the correct one for your car.

Bob

 

It gets to the 120 mark...too hot. The reservoir cap is allowing pressure and water to escape when the engine heats up. Once the car gets hot, the temp does not come back down, even if it is in motion. I have decided to purchase a new radiator reservior cap tomorrow and try that. (I do not think the cap should be allowing pressure and water to escape??) If that does not fix it, I will remove/replace the thermostat.

I read on one of the forums that the owner had a similar problem and changed the temp sending switch as well. Isn't that just an indicator? Or does it somehow control the temp of the car?

Thanks for your help

 

I'll try to address the points you make in the order you made them.

o 120 is tooo hot
o Pressure cap, in my opinion, is doing its job...acting to maintain the specified pressure in the system, which if exceeded, will allow water to escape so the system doesn't blow up.
o Still a good idea to replace the cap! If the current cap diaphram/gasket, whatever it's called, is failing to maintain the correct pressure, it's worthless. If close to a dealer, get an MB Cap. I'm an 'after market kind of guy' except when it comes to certain maintenance items; this cap is one of them.
o You might as well pick up another thermostat while you're there, I think that's where the heart of the problem is. Either bad initial part or t'stat installed incorrectly.
o Speaking of MB parts, you did put an MB OE Water Pump in, right? Thereused to bemany complaints about the impellers (I think they're called) on the aftermarket pumps. Is there any water/coolant leaking at the pump?
o I don't think the temp sending switch figures into what's happening with your cooling system

Bob

 

Thanks for the comments.
The new water pump was suposed to be a MB, but the shop picked it up.
I will take your advice and pick up a new thermostat when I pick up the cap. Hopefully the cap will fix it, but if not, I will be prepared.
I will post the results of this "round".
Mike

 

It seems to go from bad to worse.
I replaced the auxillary tank cap (radiator cap) with a new one from the MB dealer. No improvement.
I decided to take the thermostat out and check it in a pot of boiling water to see if it was working. Guess what? There was not a thermostat in it!
At this point, I have a decision to make. (I am going to assume that the water pump that was installed was either NOT new, and/or if it WAS new, was not a MB water pump. So....I can have the car hauled back to the place that lied to me about it, or, simply purchase a new MB water pump and install it myself.

Before I put on another water pump, can you think of ANYTHING else it could be? I can not imagine that there is a blockage in the water system, unless they really did not change the block out as I was told. At this point, I am not sure what to believe.

Mike

 

Mike,
Having had a similar incident awhile back over a cruise control amp, all I can say is I feel your pain and understand your frustration.

What I did, and since it worked I'll suggest to you, is the following.

If and only if, prior to this experience the shop you used had a good reputation, your immediate recourse is with the owner. Approached like any other business issue, prep'd, calm, and direct should make this come out in your favor. I would not tow the car over immediately, but rather, after you do a little homework, call the owner to tell him that his rebuild and parts installations are giving you some significant problems and you want to meet with him to go over his bill for services to get a full understanding of exactly what went into the engine work. Do not discuss the particulars of the 'significant problems' other than to say that the car isn't driveable in its current state and that you will go over everything when you meet face to face. Be business like, pleasant, and firm.

Take a look at the drawing and parts list you can get to from the link below. Pay particular attention to the location of the thermostat vs. where your logical mind may have had you looking (it fooled me the first time!)

Look over the part numbers for the water pump. The drawing is supposed to be for the 117 engine, but I noticed that the water pump carries a116 designation. All may be kosher as it's possible that the same pump goes in both MB engines. Double check this with the Parts guy at the dealer. Either give him these numbers or ask him which pump(s) will work in your car. You can handle this by phone.

http://www.detali.ru/cat/oem_mb1.asp...14M&SID=20

Compare the actual as verified acceptable water pump part #'s with your bill if it was itemized to that level.

Once you've gotten the facts straight, i.e. there is or isn't a thermostat installed correctly, and the actual MB part number for the pump and compared these items to the shop bill, make a written outline/talking pointsof the issues that you've been experiencing since you picked up the car.

Go to the meeting. State your objective at the outset; ex, the purpose in getting together today is to get the clearest understanding possible about what may be causing the difficulties you're having with the car and work out a cure plan for how these apparent problems get resolved. And away you go...

If the owner makes any statement that should be proveable, make him prove it; ex. "I used a genuine new MB water pump in your car" Your response is "Please show me the invoice or packing slip from MB". Check the part number, date of order/delivery etc. to make sure it's the one in your car. I think you probably get the drill.

If the owner of the shop values it's and his own reputation, he should be very willing to sort this out to your satisfaction. If there's any trick to this, it's staying calm and business like and listening carefully to what he says. observing body language and sticking to your talking points. At the end of your meeting, you should have agreement on the next steps to be accomplished to get the car operating to spec and the specific items the shop is going to do for you.

That's all I've got for ya, and I hope I didn't take too much liberty with the 'this is what I'd do' stuff above, Pleaseunderstand that it's just my nature to attempt to insure clear communications to the reader.

Good luck,

Bob
.

 

Bob

You make some very good points. I studied the diagram and did, in fact, get fooled when I first looked for the thermostat. But, I did finally find the right place for it, but...no thermostat. I will give the shop owner a call tomorrow and set the meeting up as you advised. And, I willreview the detailed invoice, and get part numbers from MB before I meet with him.

Thanks again. I will let you know how it works out.

Mike

 

Pull the thermostat back out ( a very simple job) and put it in a pan of water on the stove with a thermometer and see what it opens at. Should open about 190-195 or so. If it checks out put it back in paying strict attention to the direction it goes (the little cylinder faces the engine) If U put it in backwards hell will freeze over before it opens and U will crack a head or at least blow a head gasket. I learned the hard way on an old Dodge K-Kar. cause i got in a hurry. Also make sure that neither of the radiator hoses are collapsing or that the radiator isn't plugged up. just driving it and hoping it will get better will prove to be a very expensive mistake..[8D]

 

I have the same problem on an 87 560sl w/87,500 miles on her I replaced the thermostat last year, checking it before installing it. Today it ran hot enough in 80 degree weather that it stayed right against the red mark but not going into it. I never did hear the fan come on and was wondering where the fan switch/sensor is that triggers the radiator fan when the temp gets high enough to require it? never gets hot when driving it, just when stuck in traffic idiling for a while. Do you know where the switch is? Thanks, Pete Walls, Camas WA (wallsent@gmail.com)