Where is engine block coolant drainage bolt? - PeachParts Mercedes-Benz Forum

ck42 · #1 05-06-2002, 02:06 PM

The wonderful Hayne's manual shows a bolt for draining the coolant from the engine block but it's so close-up I can't tell WHERE on the block it's located. Can someone point me in the right directions here?

HGV · #2 05-06-2002, 02:13 PM

I should be located on the block on the exhuast side. A simple bolt with nothing attached to it.

Henry

ck42 · #3 05-06-2002, 02:18 PM

Henry thnx.

Also, for clarification, it was NOT the Hayne's manual, but rather the POS CD manual that showed the pix.

OH....it also showed a place for draining the radiator. I can't seem to locate that either.

HGV · #4 05-06-2002, 02:25 PM

Use the big black hose at the bottom of the readiator. I believe your radiator has a 13mm drain bolt. I once had the bolt thread fitting let loose on the radiator and I had to remove the radiator and resolder the fitting on. My 87 300TD has a nice drain cock that you can attached a small hose to drain into a container. Same with the block drain. These Germans sometimes make thing easy.

Henry

ck42 · #5 05-06-2002, 02:33 PM

Still can't locate the bolt on the engine block.

Can you point me a little closer?

Will-do on the radiator hose.

HGV · #6 05-06-2002, 02:56 PM

I will try. Keep in mind this is from memory. I recall the block drain being located on the exhaust side of the block toward the back of the block located about 2" below the block head interface. I think it is a 15mm bolt. You have to get to it from behind the engine mount brackit and in front of the drag link on the suspension. It should be clearly visible. Let me know if you find it.

ck42 · #7 05-06-2002, 03:29 PM

I found it. It's basically right in front of one end of the starter on the block.

Too much of a pain for me to think about messing with. I just drained the radiator through the hoses.

I drained what appears to have been about a gallon or so when I removed the water pump. About another gallon came out from the radiator. So, I guess that means there's about another gallon (approx) left in the block.

Until I get the new water pump in, I can't run the engine to pump the coolant out. Hmmmm.

HGV · #8 05-06-2002, 03:36 PM

I think the car has about a two gallon capacity. With the water pump out, you should have gotten all the water out, don't bother with the last few drops. It is good enough. YOu can always just fill the car with plain water, run it until the t-stat opens then drain it again. This would dilute anything that is left in the block. Then fill it with anti freeze and water. Should work.

Henry

ck42 · #9 05-06-2002, 03:44 PM

Thanks Henry.

tcane · #10 05-06-2002, 04:45 PM

The cooling system holds almost 3 gallons (11.6 qts.). The radiator holds about 3 - 3 1/2 qts. You will still have 3 + qts. or so in the block with the water pump removed and the rest in the hoses and heater core. You can drain more out of the block by raising the rear end - the more old coolant removed the better, esp. if it has not been drained in a while and esp. if you're changing to the 5 yr./100,000 antifreeze. HGV suggestion to run fresh water and then drain is a good one, esp. if you don't know when the last time the coolant was changed or if the old antifreeze in it was the new high mileage type (old formulation needed R&R at 2 yrs./24,000 mi.).

The water pump bolts are torqued to 8 ft. lbs. or so (96 in. lbs) in a criss-cross pattern. Gasket sealer is not a must, but I use a small amount of high temp silicone (Ultra-Copper by Permatex) because the engine surfaces are not new and some variations in the gasket contact surfaces may exist which could lead to leakage (I want to stress, a very small amount of silicone spread thinly and evenly). Make sure the gasket contact surfaces are clean of all the old gasket material and I clean with isopropyl alcohol. In the old days (or was that the bad old days?!?), grease or oil was smeared on the new gasket to soften it to seal better and also hold it in place (good idea if you don't want to use silicone). The new fan belt will stretch a bit in 15 min. or so of running, so it will need to be retightened (do not over-tighten to begin with because you can ruin the bearings in the water pump and/or alternator).

Good Luck!
Tom

ck42 · #11 05-06-2002, 05:02 PM

Tom, thanks for the tips. I'll get everything put back together and then run the water hose into the system to flush it out.
Any suggestions on where to put the water in and where to drain it out when doing this?

Do I need to get the coolant from MBZ in order to get the 5yr stuff?

I have a torque wrench ready and spent quite a while cleaning the pump housing surface...got out the 1000 grit paper on it too.

I've gotten mixed reports now on whether or not to use any sealant on the gasket.

Not using a new belt....looked at the service records and new belts were just recently installed....explains why still looked so good.

JimSmith · #12 05-06-2002, 06:26 PM

ck42,

Highly recommend the MB antifreeze. Did you decide where the fluid was leaking from?

I normally do not use any sealants unless there is evidence of pitting or worse corrosion in the gasket seating area. The clamping pressure distribution around and between the bolt holes can be adversely affected by by a number of things at assembly, including how tight the belt is drawn by the alternator position adjustment. Too much lateral force can unload some of the fasteners, especially if they were not properly tightened. It also wears the shaft bearings and shaft seal out prematurely. With properly tightened bolts you only really need a continuous contact all the way around the joint that is at least 1/16th of an inch thick. The width of the good surface (no pits or gouges) can get thicker, but if it less than a 1/16th of an inch, I would use a sealant. If you use a sealant take care to use it sparingly and follow the manufacturer's directions exactly. Some require a thin layer on the gasket and the mating metal surfaces, some do not.

If you use a sealant, take an extra step or two checking the fastener tightness. As the sealant is extruded into the water way area and out the edges, the torque on the fasteners can relax. When all is said and done, the fastener toque should stay at the value you set it.

As for where to put the flush water in and let it out, I usually flush the radiator for a while and then close the plug on the bottom and flush in the radiator and out the block. Seems to get the big stuff out. Last time I did it I used the MB citric acid flush stuff too. (edit: If you use the citric acid or other flushing chemicals, the directions usually tell you to fill the system and run the car to normal operating temp for some period of time. When you do this you turn the interior heat on to flush out the lines and heat exchangers fed by the coolant system too)

Good luck, Jim

tcane · #13 05-06-2002, 06:29 PM

You can remove the cooling hose located toward the rear of the head where it connects to the hard metal line on/close to the firewall and run water from a hose through the head and block through the cooling hose, and then run water through the hard metal line on/close to the firewall through the rest of the cooling system. This type of flush can be done with the water pump off or on - if you do it with the pump on, then connect all the coolant hose except the hose that connects to the bottom of the radiator, leave it off at the radiator and connected to the thermostat housing, leave the bottom mounting bolt to the water pump out and some water will run out there, then replace the mounting bolt when through flushing. With the pump off, the water hose flush will pour out the area where the water pump mounts, but will not flush out the entire head area because the head is higher than the place where the water pump mounts. Probably best to flush a bit with the pump off to get most of the old coolant out of the block along with any crud/debris and then after mounting the pump with a more thorough flush since most of the cooling system will be sealed and more areas reached with the garden hose water.

Careful with making the gasket surfaces too smooth. This is 20+ year old technology and designed to have a certain roughness measured in Ra units so the gaskets will hold and seal (more critical on the head to block gasket surface areas). I use a brass brush to polish the contact surfaces and brushing also shows any old gasket material I may have missed!

!

The problem with gasket sealer, esp. silicone, is using too much and that is why I suggested using a very small amount . If you are uncomfortable with using silicone then use a bit of grease to soften the gasket a bit and hold it in place (on the injection pump, greasing the gasket is a must since this gasket needs to be pliable and not attached to either surface so the IP can be rotated to set the start of delivery on #1 injector w/o damaging the gasket to prevent the chance of an oil leak), or use another type of gasket sealer (lots of luck with Copper Coat and Permatex Aviation Form A Gasket - but using small amounts), or mount the gasket dry. I've rebuilt well over 1,000 engines (perhaps 2,000) and countless repairs using new gaskets - so I've mounted what 250,000 - 500,000 + gaskets and always used some type of gasket sealer since a leak would cost me $ to repair over again since I was not paid to redo a mistake and, more significantly, the inconvenience to the customer and the cutomer's loss of confidence in my ability to repair their vehicle correctly the first time, or when racing costing a failure and not being able to finish a race, or at the fleet/business level and the loss of income because a machine/vehicle failed and a job could not be bid on/began/completed, or now that I'm out of the professional technician/racing fields my own time to redo a repair. That said, you do what you feel comfortable with.

Texaco, Preston and Zerex make 5 yr./100,000 mile antifreeze. Your M-B was made when the only the green antifreeze existed, so the green stuff will work fine. Zerex is green. Texaco and Permatex are the orange color antifreeze. The orange was made originally for GM applications (GM's Dex-Cool as I recall). Now the orange is formulated not only for GM, but also Japan w/o silicates and Europe w/o phosphates to name a couple of other applications/formulations this antifreeze is made for. Wal Mart just began selling Preston and the label said M-B approved (not on Texaco). However, Preston's M-B application is for the newer models that have plastic cooling parts that are sensitive to certain chemicals in antifreeze that require the orange antifreeze as well as specific pH levels. Also, I use distilled water to make my antifreeze mix (M-B spec 55% antifreeze, 45% water).

The thermostat is another area to consider looking at. Stats get old and fail. If you're so inclined, take the stat out and immerse in hot water at 200 F. It should open fully in about a minute. If bad replace. Check a new stat because they are bad brand new even from M-B (look up a leathermang post about finding all defective new stats at his local M-B dealer), and I've found my fair share of bad new stats also.

Good Luck!
Tom