Hiya Everybody! Bought an 86 300E 2 weeks ago... and so it begins
 

Hiya all,

We purchased a 1986 300E a couple of weeks ago at a great price. The car is in beautiful shape inside and out, and has driven beautifully since we acquired it. Of course being a 25 year old car it is not without it's issues, most of them seemed minor however, and I had planned to repair them all as my time and budget allowed.

Well, last night my repair schedule changed a bit. As I was on the highway we started to smell coolant, then the belt started squealing like crazy. Looked down and saw the coolant temp gauge was pegged at 120. I was on a bridge with no breakdown lane so I had to keep driving until we cleared the bridge. Before we made it over to the other side a cloud of steam blasted from under the hood. Needless to say I was assuming the worst.... blown headgasket, warped head, seized engine.

Got her to the side of the road and shut her down. Popped the hood and saw that the upper rad hose was disconnected. Upon further inspection it seems that the plastic flange on the rad that the hose attaches to broke free. Rad is toast. Best price I could find on a replacement here in Canada is $250, Tuesday at the earliest since it's a holiday weekend here.

I'm assuming the belt was squealing because it had been sprayed with coolant. Hopefully nothing more serious going on.

Luckily the car still cranks and starts (although I didn't leave it running for more than a second). Hopefully that means I got her shut down before any serious damage was done.

Anyway, I got the section of the service manual for R&R'ing the rad from 124 zone's website. Seems pretty straight forward, but having never spun a wrench on one of these cars I figured I'd ask the pro's if there is anything I need to know before DIY'ing this.

Thanks in advance folks, and wish me luck. :)

Welcome to the forums.

Not to burst your bubble. But I can almost guarantee that the head gasket is blown, which will allow oil into the coolant or vice versa. These engines do not like hitting 120C, let alone staying there and driving. There was actually a design flaw in the original head gasket which makes them susceptible to blowing. I purchased my car with a new rad and blown head gasket, same story. :)

The car will be driveable with a new radiator alone, but your cooling system will be heavily contaminated within a few hundred miles. The head gasket job is a fairly involved repair, but not out of the reach of a DIY'er.

I wouldn't worry about head gasket yet, the OP hasn't stated any history with the car, and it may have been replaced already anyway.

Just get a new radiator, Behr or Nissens ONLY (I personally like Nissens), do not get any aftermarket junk. I did it in the beginning and regretted it after replacing it 3 years later.

Coolant is Zerex G-05 -- again, don't get generic crap. Find the correct stuff and your water pump will last and perform better for longer, its tried and true.

Change the oil immediately, overheating causes additive packages to become extinct. Use 15-40 diesel oil such as Rotella-T 15-40, Delvac 15-40, Delo 15-40, I'm partial to Rotella-T and Delvac. The 86 103, unless changed under warranty, will probably still have the pre-hardened cam and it is susceptible to scoring and wear. The zinc additive is a must that is within the above oils!

If the worst has occured and the HG is gone, its not too difficult of a job if you leave everything alone other than the gasket. You don't have to mess with timing, even the belt tensioner you leave alone. Its straight forward if you have some experience wrenching.

DroogBC, failure of the upper radiator hose connection is a common occurrence with older radiators. The replacement Behr radiator should have a metal-reinforced upper hose connection. As mentioned I wouldn't immediately presume the head gasket has failed, although that is a possibility.

Be sure to use either MB coolant or Zerex G-05 (both have a neutral PH) mixed 50/50 with water. When refilling the radiator use a short length of clear hose (same size as radiator hose) turned upward so it acts as a funnel, and allow all the air to bubble out before connecting the upper radiator hose. With the clear hose it's easy to see when the radiator is full, but you could also use the upper radiator for the same purpose. Only then you're flying blind. You may want to install a new thermostat while you're at it.

After reassembly run the engine up to operating temperature. Then let it cool down and check the coolant level in the expansion tank. Add coolant, as required, to the full level. You should check the expansion tank level regularly for a while to make sure it's stabilized, and that no oil is in the coolant. Also, check the dipstick for signs of coolant in the oil. Either one would be the sign of a failed head gasket.

Why diesel oil? I thought the zinc additives were bad for cars with cats ( assuming his 86 has one).

Thanks a bunch for the insight folks, I really appreciate it. Although I only drove it while overheating for a moment or two while looking for a safe place to pull over, it certainly seemed like an eternity to me. I'm really hoping the HG isn't toast, but I guess I'll cross that bridge when I get to it. I did pull the dipstick yesterday and the oil is still oil colored, no creaminess or milkiness but I guess it's a little early to tell.

I'll be sure to use the appropriate coolant as suggested, and will do my best to purge the system as recommended. Hopefully I don't run into any problems swapping one rad for the other.

... about that oil. I never would have thought to use diesel oil in a gas engine. Pardon my ignorance, but what's the deal with that?

I'm assuming my 86 has a cat, but I haven't actually climbed under there to check. I guess I'll have a peek tomorrow, lol. I do know that the car passed emissions testing a couple of weeks ago, so that's always good. Everything was well under the allowable thresholds... not bad for 347,000 KM.

Check for mayonnaise under the oil filler cap and do a cold compression test.

Doesn't the M103 have a coolant bleed port in the head near the upper radiator hose fitting?

Sixto
87 300D

There is a bleed screw on the top of the thermostat housing, unless that particular m103 is equipped with the junky black plastic thermostat housing. Most have the aluminum housing, I'd highly recommend replacing the plastic one with an aluminum unit is to equipped.

Yes, right next to the valve cover.

Just took a look and the current rad is a Behr K5 and seems to have the aforementioned metal bit where the upper hose connects. Was it an old rad, or overtightened hose clamp. Hmmmm.

I see that I have an aluminum thermostat housing. I see the bleed screw right in the center. Very handy. :)

Glanced under the car and I do appear to have a cat... or at least a heat shield roughly mid-pipe where a cat might be. hehehe

How do all of those clips holding the rad in place work, anyway? I haven't begun to fiddle with them much thus far, just wondering if they simply slide upwards or if they lock in place somehow. Any trick to removing them? Just want to mitigate any potential first timer damage. lol

No mayo under the oil cap... just normal looking oil.

...Oh, about that oil...

Too much, yes.

You wanna prolong the life of your valvetrain or your cat?

Replaced the rad a little while ago then filled the system and fired her up. She got hot quickly, but no heat coming from the vents inside, and the left side of the rad feels cool to the touch.

More worrying is there is lotsa squealing going on and the source is the below pictured pulley which isn't spinning. That's the water pump, isn't it?

yup, thats the pump, that explains why no heat - because its not turning the impeller must be jammed or corroded internally and you won't want to run the engine more than a fraction of a minute. Why did it stop turning all of a sudden?

re-read this thread and saw a piece of plastic inside the rad hose where the neck snapped off the old rad. I see you figured out how those clips that hold it in work. Is it possible a bit of plastic got sucked into the water pump? This is highly unusual (a jammed impeller) :confused: