I'm Not Sure If This Is A Head Gasket Problem ...

[Turbowagon245]

I've been working on my friend's 1991 240SE wagon for a while now, and can't seem to figure out what the problem is. Initially, the temperature gauge would fluctuate from the 9 o'clock position, all the way up to the red, and it would then come back down again. Usually, it would get hot when the car was at a stop, or going up a big hill. When I first looked under the hood, I noticed that the water pump was leaking quite a bit; so, we replaced the water pump and thermostat. The radiator is not leaking, and the hoses are fine. This seemed to fix the problem for a few days.

Now, it's doing the same thing, but with no consistency...sometimes it gets hot when on the freeway, sometimes during city driving. She told me that there was "smoke" coming from under the passenger side of the hood a few days ago...I drove it with her a few days later, and noticed that this seems to be coming from the block, near the passenger side firewall, just below the exhaust manifold. I'm almost positive that it's actually steam, not burning oil. There's not very much of it (yet), but it is definitely there. The antifreeze still looks clean, and there is no milky residue under the engine oil cap. I do think she mentioned that she lost a little bit of coolant over the course of this past month, though I do not think it was a large amount.I

Does this sound like a failing head gasket? I think the car has 300K+ miles on it. I know she drove it for a while before she asked me to look at it the first time, so I'm guessing that the engine ran hot for an extended period of time.

[Three Fat Tigers]

The head gasket can fail in this manner where it vents coolant only outside the block, but it would be an extremely rare event. When it goes, it usually will fail full time, not randomly where it magically seals itself again.

Other possibilities would include the heater return pipe that runs from the water pump, under the intake manifold and around to the back of the head. Perhaps it is rusted where a pin hole has appeared, or a fracture, or maybe the heater return hose has an issue where it attaches to this pipe behind the head (I'd start by reaching around the back and see if you can feel any coolant around this spot). Or maybe a block freeze plug is beginning to fail. One means of isolating the leak would be to clean the area of grease and dirt as best you can (gunk engine cleaner + pressure washer), let it dry then throw some baby powder/flour all over the area, test drive then crawl under for a look. For reference: Heater Return Pipe

Whatever the leak, it sounds like it's being triggered by the overheating, which could be caused by one or more of the following:

→a failed fan clutch:

Check the clutch, start with a stone cold engine and rev the engine a little until you hear the fan roar die off (normally something like 30 seconds), then shut off the car; turn the fan by hand and get a feel for the resistance in the clutch. Then run the engine until nice and hot (normally hard to do in cold weather), could take 30 min or more in warm weather; shut down and again turn the fan by hand, it should be significantly stiffer than when it was cold. Should it need replacing, do not buy the tropical fan clutch unless you really like the sound of fan roar.

→a problem with the radiator:

Internal corrosion where the flow rate is significantly reduced (replace radiator or have it flow tested/rebuilt). And or externally where dirt has built up in the fins (remove fan shroud and back flow through the fins with a heavy flow of water from a garden hose). Should it need replacing, don't bother buying the all metal three row type, there is no advantage to that design.

If not for the steam and loss of coolant, I would also have suggested a fault in the temperature gauge compensation board (easily bypassed). A faulty reservoir cap can also add to this soup but would not likely cause the overheating by it self. Should it turn out to be the head gasket, do not skip having the head checked/resurfaced as odds are high it will need it.

[Turbowagon245]

Thanks for the pointers! we're going to check it out today. Should it be the radiator, do you have any recommendations on the vendor? I noticed that advanceauto (which would be much more convenient) sells them for about $100, while fcpgroton sells them for $180. There was only one review for the advance model, but it was not very good.

I also noticed that the fan clutch is only $60, which makes me think we should just go ahead and replace it anyway, especially because it is so accessible. Any tips on the radiator replacement? I assume it should be fairly straight forward.

[Three Fat Tigers]

Advance doesn't state a specific warranty for their radiator and typically their warranties are not anywhere near as good as Autozone. The one from Autozone does have a life time warranty and it's the same price. I have the Autozone one in my '92 240 and it works great, the quality was very good, no complaints at all. Otherwise Nissens would be the brand name to shoot for, http://www.eeuroparts.com has the Nissens for 165$ shipped. I've sent you a PM with another much cheaper source.

Both Autozone and Advance have the fan clutch for 38$, but again Autozone is lifetime and Advance is only one year warranty. Don't know if I'd be eager to buy a new one if my old one was still working. If it's really cold where you are, a defective fan clutch would be less of a factor in this overheating issue as the radiator should still have an notable over capacity to cool the engine. Volvo even sold a blanket to put over the grill to block cold air from over cooling the radiator, where under bumper air flow to the radiator was left unobstructed.

On the radiator install: the fan doesn't need to be removed, just loosen the fan shroud and move it back. The trans cooler lines (assuming you have an automatic) are 15mm, and can be terribly tight; they are attached to fittings that are themselves just screwed into the radiator; you do want to have a large open end or adjustable wrench to stop those fitting from backing out. Have some baggies and clothes pins to place over the lines as you remove them, they should leak too much though, the radiator will dump out a bit of trans fluid out of the lower fitting, so be ready for that. Might apply some anti-seize to the trans cooler lines around where the nuts are to avoid rust that can make the difficult to remove in future. Under the upper mounting brackets are (normally) little tube like spacers that the bolts pass through to keep you from crushing the bracket, try not to loose them. The bottom corners of the radiator sit in rubber spacers which might come out with the radiator, just want to make sure they are in place down on the frame before you replace the radiator.

As for coolant, you want to drain the block (13mm nipple on the right side of the block below the exhaust manifold) or flush the block with a hose, then add in the proper amount of coolant (not the 50/50% stuff), then top up with distilled water.

Personally I would start with a stone cold engine, turn the heat control to full on, remove the splash pan, drain via the lower radiator hose, then open the drain on the block until it's drained, reattach the lower hose (usually no need to re-tighten the hose clamp at this time). Refill the system with distilled water, start and run the engine for 30 seconds or so, raising the the engine speed slightly, then shut it off. Repeat this 2-3 more times. Then reassemble with the new radiator and refill with 5 qts of coolant (IIRC it's 9.7 qts, so that's about a 50/50 mix), then top off with distilled water. If your coolant isn't very old, you can jack up the front of the car and capture the coolant in a bucket, then re-use it, not sure if I would do that though when replacing the radiator.

You could also remove the coolant reservoir and clean it out, might leave it in a bucket of hot water and oxyclean for about an hour.

For the fan clutch: I'd grab a medium large rubber type strap wrench to use on the water pump pulley to hold it while you loosen the 10mm nuts holding the fan clutch.

Other:

Cooling system spikes are usually caused by a defective thermostat, but as you have replaced that, odds are it's not a factor, but I have on more than one occasion purchased a new thermostat that turned out to be defective, causing odd overheating spikes. If you don't have a splash pan, it can improve cooling air flow, as does the air guide (often missing) that goes between the openings in the air dam under the bumper to the bottom of the radiator.