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.

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2003 Gray Mercedes ML350 - 122k

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.

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Fred Hoelzle

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

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Prost!

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.

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Too much, yes.

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

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k