1992 / 740 Wagon / 220K+ miles. Reasonably well maintained. Until recently the car had run well and started very reliably.
I was returning home last Saturday from a shopping trip -- so the engine was warmed up and running fine.
I was slowed down from 30->15 and was making a 90 degree turn into the subdivision from the main road.
At first I thought the steering system had failed but an instant later I realized that the engine had stalled and I was coasting around the corner. I coasted to a stop and the engine restarted after a couple of tries. I drove the last half mile rather gingerly but the car made it back to my house and it's now sitting in the driveway.
I haven't driven the car for the past few days, but I since I made it home I think it's fair to say the problem is intermittent.

1) How should I go about diagnosing an engine stalling problem like this?
2) I don't think it's relevant to the engine stalling, but on inspection I notice that there is quite a bit of oil in the coolant reservoir. There is a black sludge-like layer floating on the coolant. I have noticed traces of oil in the coolant for the past few months -- but nothing like this. Other posts on this suggest a blown head gasket (or possibly a bad radiator?). However, there is no evidence of white fumes on startup, the engine oil looks fine, and the car starts up very well and no recent noticeable reduction in power. The car does not leak oil, leave oil patches after parking, and I can't see any obvious evidence of oil or coolant leaking from the head gasket.
So what's the best strategy to diagnose this issue?

Much obliged --

 

I have a 240 wagon, I had the same problem....as I was turning the engine would just die...and yes, it was weird like it just "gently went to sleep".

replace the brake booster check valve....cheap part from the junk yard or cheap part from the sponsor. here is a picture...

I read a post that worst case scenario would be the power steering pump...around 50 to 60 bucks...

 

The oil pressure for the cam goes thru the head gasket, so probably there is a tiny leak between the oil and water passages. I'm thinking it's unrelated to the stalling problem.

Stalling might be a couple of things I can think of...

One is that you have a short in the wiring harness, such that when you turn the wires are grounding out.

Or, your in-tank fuel pump is dead and you're vapor locking between it and the main pump...

 

I use to have a 740 GLE and it use to stall when coming to a stop. It was mainly related to the throttle control valve getting sticky from being dirty. I use to have to clean it every 10,000 miles or it would cause me to stall.

As for the oil substance in the coolant, I also think it is un-related to stalling.

As for the in-tank fuel pump, you can usually hear that pump operating when the car has less than 1/4 tank of gas. But it usually would not make the car stall, just be hard to start when warm.

 

I can never hear the pumps, if they be bosch. Other brands I can hear.

When the tank pump died, the main pump got noisy and would stall. With a new tank pump, everything was quiet again.

My idle control valve would make the car stall when cold and the throttle plate was dirty, but never once I got moving.

 

Whether or not the oil in the coolant is related to the stalling, it bears further investigation.
These engines have a long, slow cylinder head gasket failure mode that does this exact thing. Black, sludgy oil is not a leaking transmission cooler and if it was, the transmission would be shot by now. There are two ways to get black, sludgy oil into the cooling system, pour it in, or inject it under pressure through a gasket leak with combustion chamber gases.
You won't notice any big symptons. Maybe you've had a random misfire when hot idling for a few seconds at traffic lights, topping coolant up a little every 2-3 months? A really lumpy idle for a few seconds first start of the day?
I'd at least have the cooling system pressure tested and hydrocarbon tested. When they go, it requires immediate attention and will possibly destroy the engine if it's hot at the time and you don't catch it fast enough.

Regards, Andrew.

 

Typhoon -- Looks as though you were right about the "long, slow" cylinder head gasket failure mode. The other day it stalled again, I had it towed. Then I checked the next day by running the engine until warm in the driveway and there was vapor coming from the water pump area (that would explain the odor of coolant I have noticed around the thing for the last year or so). Pulled spark plugs 1 & 2 -- black electrodes / yellow - green on ceramic.
My next door neighbor diagnosed head gasket and he said it probably stalled owing to lack of compression. Pulled the head last week and sure enough -- blistering and corrosion of the gasket around cylinder 1.
Quick question -- I am putting the new gasket on soon -- should I use a gasket sealant? If so, which one and how much of it?

Thanks --

 

I'd send the head out for a quick skim of the gasket surface, it's worth it, I had my head skimmed same day, dropped it in on the way to work, picked it up on the way home, so it won't be a big inconvenience.
I didn't use a sealer, if the head surface is machined and you get the block nice and clean with scrapers and solvent, it'll work just fine. Some people like Hylomar on head gaskets, if you do use it, only use it on the engine block, the aluminium cylinder head needs to be able to "slide" around on the head gasket as it expands much more than cast iron, plus gets hotter than the block. Gasket sealer only makes expansion tear the gasket apart over time.
May I suggest that now is a great time to replace the water pump, they're cheap and it's a much easier job with the head off.

Regards, Andrew.

 

Just to complete this story -- I installed a new head gasket (my blow-by-blow travails on this are recorded at http://www.matthewsvolvosite.com/for...hp?f=2&t=27543) and the car is running with slightly more power and hasn't stalled yet. The head gasket channels were indeed perforated around cylinder #1. So this would appear to be a case of stalling in traffic because of lack of compression. Thanks for your comments -- all very helpful --

Rob
Charlottesville, VA