This car man, I swear...

A while back, I noticed a coolant leak from the block of my engine, but with the helpful advice of the good folks here, I did a fair Head Gasket job. Afterwards, I noticed I was running through coolant pretty quickly, but could never find a leak. I replace the Water Pump and the lower radiator hose that was oil damaged and thought that fixed my problem.
Nope.
I was running through coolant almost as much as I was before, and the car started getting pretty hot (not to the red, thankfully) yesterday as I was pulling into a gas station. After I pumped my gas, I saw a river of coolant flowing out from under my car.
I looked under the hood and it looked like the same corner of the engine that sprang a leak last time, so AARRGH I gotta do another Head Gasket job. So I panic-bought two gallons of anti-freeze at the gas station (wrong kind, but I just needed to get home) and went straight home. I hopped onto my computer and ordered some gaskets from O'Reilly, and did a coolant flush. Later I'll go down to O'Reilly and pick up my order.

HERE'S MY QUESTION: When I replaced the Water Pump, the Heater Return Pipe was stuck to the old Water Pump, and stuck pretty good. I can't remember how I got it off, but I think it required leverage with a screwdriver, and the old gasket was hard as a rock and required extensive scraping to get the pipe clean. When I got back home with the car yesterday, I put it up on ramps and took a look. The coolant appeared to be coming from behind the engine, right where the Heater Return Pipe passes behind the head block. Could I have opened up a leak at the junction of the pipe to the hose by wrestling the pipe around trying to get it off the old Water Pump? I cannot see where the pipe joins the hose, cause it's back there in the mystery zone obscured by wires and hoses from the Fuel Injection system. Any advice on how to find the junction and diagnose it? Or did I simply do a sloppy Head Gasket job, and a re-do is required?

 

I think it unlikely that you damaged the rear pipe by struggling with it at the water pump junction.
If the leak is at the back, lift the car and get under there with the light and see where exactly it's coming from, sounds like the leak now is pretty big. It could be one of several water pipes back there. I doubt that it is the head gasket-- it'd run poorly if at all if that was the case.

 

a common source of coolant leaks are the heater hoses, and heater valve, whihc on a 740/940 is between the engine and firewall (on a 240, its inside the firewall at the bottom of the center console near the gas pedal).

 

I don't have any coolant leaking inside the car, so I think the heater valve is OK. It's one of the old-style metal ones, apparently those have been superseded by a plastic one.

I probed around with my phone camera trying to get a good look at what's going on behind the engine, and it's looking more and more like it is a Head Gasket leak, because what I could see of the hose/pipe connection looks dry. I don't know, maybe I bunged up some corner when I did it last time, who knows. I'm going to re-do the job tomorrow and just for good measure, I'll replace the heater hose while the head's off and I have much better access to everything back there.

 

The heater valve is not inside the car so it has nothing to do with the heater core leaks.
You cannot tell where the leak is the way you are doing it.
There is a heater hose that attaches to the head under the intake manifold, hard to see but it'd look like a HG leak...
It's up to you but before you start a new HG job, get under the car, run the engine and verify where the leak is. As you describe it, it should not be hard to find it. That's what I'd do.

 

It's a 1990 240DL, I'm pretty sure the heater valve is inside the firewall, at least that's what the interwebs tell me, and there's nothing but hoses between the inlet/outlet pipes and the engine outside of the firewall.

I took your advice, and didn't see any immediate leaks, just a very slow drip from somewhere. I got out from under the car and looked around wherever I could. I wiped some oil off of where I thought the leak was (it looked wet, but turned out to be just slick oil), and didn't see any new fluid there. I tried finding the hose you spoke of, but couldn't see it, so I jiggled the inlet hose next to where it attaches to the Heater Core nipple at the firewall to see if I could see a corresponding jiggle somewhere in the tangle. I didn't see any jiggle anywhere, but I DID hear a hissing/gurgling noise. I turned the engine back on, turned the heater OFF, and jiggled the hose again. Lo and behold!, the noise was much louder, and just below where it sounded like the noise was coming from, I saw water dripping out at a good clip. I think you've identified the culprit...

So, I'll need to go get another hose, but that's no problem and simpler than another Head Gasket job. From what glimpse I could get of the junction between the hose and the Head, there isn't a hose clamp there. Should there be?

 

for sure, on a 240, the heater valve is inside the cabin as I said, I'd only mentioned the valve because you didn't say this was a 240, and 740/940 use a vacuum activated heater valve on the outside of the firewall.

And, yeah, I'm pretty sure there should be hose clamps on there. not the screw/helical kind, but the crimp on kind, which provide a more positive clamp. at full operating temperatures, the coolant is under some pressure, like 10 PSI or so.

I would as a matter of principle replace BOTH heater hoses, since if one has failed, the other is likely not far behind.

 

All I have is the screw kind, so that's what I'll have to use. I plan on replacing the other hose as well. If only it weren't in such a tight spot... I'll have to get a bore scope to look back there and see what I'm getting into. From what I could see with my phone camera, there's a cable or two zip-tied to the hose, so I'll have to nip that before I can even get the thing out, then there's the task of threading it back behind there...

Well, I'm off to start digging in, thanks for the help everyone!

 

Now I feel like a dunce. I pulled the intake manifold up so I could see the hose. It was loose and barely stuck on the end of the nipple sticking out of the Head, and the hose clamp was loose. Most likely I neglected to tighten that thing back down when I did my Head Gasket. The hose looked in reasonable shape, and the replacement hose I got was the wrong shape, so I opted to simply push the old hose all the way back down and tighten it up real good. It ain't moving now. I'm going to invest in a bore scope so I can see how things are with the return hose behind the Head and deal with that later.
Now I gotta go looking for the intake nut I lost...

 

Sorry about the heater valve location misinfo, I was thinking of a 940/740!
Glad you found the leak, that particular hose miss is common after a HG job...

 

Eh, no harm, no foul.
I got everything buttoned back down, took her for a spin a few times around the neighborhood, down the freeway a few miles, and I can confirm there are no leaks and the temp gauge read just a hair below dead center the whole way (I bypassed the temp-faker board, so it reads analog temp). I never did find the lost intake nut, but I had a spare, so no worries there. I think we're done here.

 

Hi Guys,
I found your thread and it exactly describes my 1990 DL issue to a T,..... less the HG job.
I just made it home after doing some errands with most of my coolant on the trail home. Basically a leak without warning.
Changed the water pump, had the rad checked, bought new hoses and coolant and buttoned it all up today and gave it a start and 5 min later had fluid
dripping and spraying out on the back left side (drivers) heater hose country.
Will try getting photos of where the drippy, hissy action is before I start to tear it down.
Thank you for describing and solving ...hopefully, mine is the same culprit.