hilarious issue with the 940 (coolant on the ground/pressure)

[linuxman51]

Pretty early in the diagnosis of this ailment (whatever it may be), so initial information is going to be a little sparse.

background: 1991 940 turbo (project bpu), recently replaced transmission..as in monday night recently replaced.

no obvious transmission leaks across two separate trips yesterday, no drips or drops in the driveway yesterday afternoon. Today, while outside with the 3 year old I noticed what looked like a puddle underneath the car.. but a little forward of where you'd expect a transmission leak. rolled the car backwards, and based on the taste test and 'look', it's not atf, but rather coolant.

Immediately suspected the heater control valve (it's not ruled out yet, but not obviously failed either), popped hood and was surprised to see it still where it belongs, and further, intact. it did appear that the source of said coolant came from somewhere on that side of the engine bay, but still not able to pinpoint. Transmission bellhousing was clean.

In checking the overflow (to verify/see), I noticed that the cooling system was still very much pressurized despite the car having sat for ~15 hours give or take. pressurized like sprayed coolant out when I loosened the cap. overflow looked kinda cruddy, but not really any worse than it's looked the whole time. coolant level was indeed low, but I also have a slight heater core leak these days, and of course, this puddle on the ground. topped it up, cranked the car up, noted what sounded like one cylinder deviated from the rest, but nothing glaring there. at idle, it's not obviously pressurizing the cooling system, nothing strange in the oil or under the cap. let the car run up to operating temp, and nothing strange there either. so I'm at a bit of a loss on this right now. I'll probably run a compression test on it later this afternoon (it also developed an occasional/intermittent low speed miss recently, but that seemed at the time to be more attributable to a coil flaking out in cold temps, as it would go away once the car was warmed up and driven a couple of miles). With the lockup converter locked up, I also noted a 'bumping' sensation at low engine speeds while cruising. I attributed that to perhaps overzealous timing advance, but maybe not?

no strange stuff out the tailpipe, car seems to run fine at WOT the brief bit I've hit it the past two days, nothing has gotten obviously worse. I still like my coil idea regarding the miss, but I'll have to let the plugs convince me I reckon.

any other thoughts as to the source of the coolant on the ground?

[Dicktater]

Does your 91 have the water cooled oil cooler? and does the leak seem to be on the right side of the car?

[JohnMc]

My son's 940 puked a LOT of coolant out from the oil cooler a month or two ago. Those poor coolant hoses get oil and turbo heat, they live a hard life.

[Dicktater]

Been there and done that. You also want to catch it before it goes poof.

[linuxman51]

no, 91 is still the '740 style' oil cooler. it looks like it's in the middle under the engine, which would be consistent with anything hitting the block and running down. I'll probably toss it up on the lift in a little bit and look closer, gotta spend a little more time working/aggravating before I go out to play.

[2manyturbos]

I didn't see any mention of ever replacing the head gasket. I have done head gaskets on B230s that would leak to the outside of the engine and then stop leaking when a piece of crud blocked the crack in the head gasket. Both cars ran fine and never overheated. One of those 2 I actually saw peeing on the ground out of the head gasket and then it shut off. Caught you MOFO.

[linuxman51]

Originally Posted by 2manyturbos

I didn't see any mention of ever replacing the head gasket. I have done head gaskets on B230s that would leak to the outside of the engine and then stop leaking when a piece of crud blocked the crack in the head gasket. Both cars ran fine and never overheated. One of those 2 I actually saw peeing on the ground out of the head gasket and then it shut off. Caught you MOFO.

that was one of my thoughts actually when I noticed the heater valve wasn't busted. I have not had the head off of this car (Was kinda hoping to avoid it, even though it'd be like a 30 minute deal, it's a slapper and the whole shooting match was going to get freshened up at some point).

[gsellstr]

I'm with Roy. Mine actually spring a leak around #4 exhaust side, no other symptoms though, and it didn't fail there on the next gasket.

Now, that said, that doesn't explain the really high pressure when cool. Kinda makes me wonder if it pressurized from a failed gasket while under boost but settled back in off boost and when cool. A quick block check with the blue dye will easily tell ya the answer there though.

[Mr. V]

Lots of possibilities, but if enough coolant leaks at the heater core there should be a drain hose for it and that might be what you are seeing.

[linuxman51]

pulled plugs and did a compression test (not that I expected anything, but.. why not. first steps and what not).. 150 150 140 150 (1-4), plugs looked fine. ran the car up on the lift, didn't see anything obvious (other than a couple drips on the block and bellhousing that hadn't dried up yet), all things point to something that happened on the driver's side. still kinda sus of the heater control valve, in looking closely (Without taking anything off) at the head to block area, I don't see where it could've come off there, and spilled atf on the heater hose there is kinda clouding the picture a bit. the hoses are new--replaced them this fall when one blew up on the dyno--but I didn't replace the heater valve, it looked alright from a wear and tear perspective.

also found some of the chra bolts loose on the ol turbski, will address those after dinner at the same time I stab off the heater control valve.

[linuxman51]

Originally Posted by Mr. V

Lots of possibilities, but if enough coolant leaks at the heater core there should be a drain hose for it and that might be what you are seeing.

that'd be on the passenger side tho right? same spot as the a/c drain?

[Mr. V]

Yes.

Perhaps the leak is where the rubber heater hose meets the metal pipe at the rear of the engine?

[linuxman51]

I believe I've isolated the possibilities to the heater valve, and moreso perhaps a clamp that was not on tight enough. that's what I'm telling myself, at least, whilst carrying around the necessary items for a bypass and road-side refill should I be incorrect about that. I also have a new valve on order (I have/had one around mountain meet timeframe, but I don't recall if I gave it away or just plain lost the damn thing). may run with the expansion cap loose for a few days to bring down the system pressure, and attempt to refrain from driving like a hooligan in that time frame.

[gsellstr]

That pressure thing long after it cooled still befuddles me. I've had a little residual in mine usually, but not enough to bubble coolant out.

Fingers crossed it is just the heater valve. I did have to mod my Astro valve a little, as the shaft would slide out under high pressure, since there's no keeper on it, then it would piss past the oring. Ended up being able to mod an injector clip and a couple tiny grooves on the body, clipped it together, and kept that thing from sliding out now. That one was weird, had the drip under load and sitting, but didn't look like anything was wrong otherwise. lol

[sbabbs]

Bigger water pump pulley and black 240 radiator cap helps to not blow stuff like heater cores and plastic heater valves and leaks from weak hose clamps. As per banned james, fyi..

[linuxman51]

Originally Posted by gsellstr

That pressure thing long after it cooled still befuddles me. I've had a little residual in mine usually, but not enough to bubble coolant out.

Fingers crossed it is just the heater valve. I did have to mod my Astro valve a little, as the shaft would slide out under high pressure, since there's no keeper on it, then it would piss past the oring. Ended up being able to mod an injector clip and a couple tiny grooves on the body, clipped it together, and kept that thing from sliding out now. That one was weird, had the drip under load and sitting, but didn't look like anything was wrong otherwise. lol

apparently that's not uncommon (the pressure thing), sam indicated his car(s) routinely do that. car was fine in a trip across town, RE the black cap, probably not a bad idea either.

[bobxyz]

Sam hasn't been lurking in the shadows with a box of alka-seltzer, a half full jug of used antifreeze, and a big grin has he?

[PCH]

Originally Posted by sbabbs

Bigger water pump pulley and black 240 radiator cap helps to not blow stuff like heater cores and plastic heater valves and leaks from weak hose clamps. As per banned james, fyi..

5/16 restrictor inside the head outlet hose will save the core and the plastic valve. In stock form the heater valve acts as restrictor even when fully open- that's why it likes to blow up so much.

[ZVOLV]

Get a pressure tester on there.

[VB242]

I had pinholes in my 940 steel heater pipe that goes from the water pump around the back of the block.

[kyote]

Originally Posted by ZVOLV

Get a pressure tester on there.

+1

I have a harbor freight special that I was able to modify a spare cap to use to pressure test Volvos.