Losing coolant, not burning

LittleJohn · Oct 9, 2017

'96 2.3L 2WD over 200k mi

Never checked the actual radiator fluid except for when I bought the truck 2 months ago. I've always just looked at the resivour. About 3 weeks ago I noticed it was empty but that turned out to be the hose got disconnected rubbing against the air intake so I used a hose clamp and thought it would be fine.

This past weekend I notice it's empty again and realized I never looked under the radiator cap and when I did it was just about empty. I had driven it over 120mi that week without any overheating, no burning smell, no smoke/steam. The temp gauge never goes over 3/4 which is only when I'm sitting still. I'm amazed I didn't toast my engine.

Filled up the rad, drove it about 30 mi the next day and lost maybe 1/4 in the fill tube on the rad. Again, never saw or smelled anything and have not noticed any big drips (it leaks a good bit of oil so I might have missed coolant in the oil puddle)

Under the hood, I found a hose with some yellow/green sludge (old coolant) kind of solidified on the bottom running all the way to the lowest point, traced it back and I think I found the leak. It's at a joint where three hoses come off and I think they go to the heater core (one goes to the firewall and all of this is on the passenger side close the blower motor) Maybe the clamps are bad, or should I just replace everything right there? (The hoses, clamps, and plastic joint.)

adsm08 · Oct 9, 2017

Heater bypass valve. Common failure item.

Mark_88 · Oct 9, 2017

That certainly could be your leak. I didn't have that setup on my 96 as mine just went into the firewall where the heater rad was located. I also transplanted the 96 heater box into my 88 so everything was there that came with the 96...

Looks like a plastic fitting though...probably cracked or broken as they do become brittle over time. You might be able to order one if you can't find one in a local yard...or make one up out of other fittings if needed.

Check the on-line manual if you haven't already done so...the link is in my sig...I decided to start carrying it with me since I refer to it so often...

tomw · Oct 10, 2017

Clean the hose with the drip line on the lower side so anything new will be obvious, start the engine and run it to normal temperature. Observe the hose, or use a hand on the underside to feel for seeping coolant. However much is coming out at the valve doesn't seem to be leaving a lot of mess. The leak may be here or may be elsewhere. It does appear as if the lowest(closest) fitting has a crack where the tube merges with the valve body, just above the end of the hose. I'd wipe that clean, and observe as above, and likely have a new valve in hand along with some new clamps, and maybe some new hose.
When/if you go to replace the valve, if you are not replacing the hoses, try twisting them on their fittings after removing the clamps. Pulling straight off does not seem to work as well as giving them a good twist to break them loose. If you are replacing the hoses, you can slit them longitudinally, from the valve towards the hose, and the split will make removal easier.
tom

BarnesAM · Oct 30, 2017

That does look like a leak. As was said already said, you may want to run the truck till it reaches regular operating temp (fill up the radiator first, of course), then open the hood and see if you can observe it dripping from there. Try it with the heater running all the way on (full hot, full fan), then with the air conditioner fully on.

That plastic valve is a bypass system that is designed to close off the coolant flow when you turn the AC on. It helps make sure your AC can blow as cold as possible. Trucks that don't have AC obviously would't have that valve, and those hoses will just go directly through the firewall and into the heater core. The valve itself is pretty cheap on rockauto.com (under $20 if I recall right), so worth it just to replace if it appears to be leaking at all.

The reason I would say to try to observe the leak is that this valve might night be the main source of losing as much coolant as you're talking about. You may want to also look at the your AC condensation tube, which is a short metal pipe-looking thing sticking out of the firewall below where those hoses go through. If your heater core has sprung a leak, you may see coolant dripping out that hose (happened on my 97). Make sure your AC is off, or you'll see water (condensation) dripping there, which is normal. If your heater is running, AC off, and there is still stuff dripping out of that tube then you want to get something under it and catch it so you can take a closer look (be careful, as the tube is right near the exhaust header). If it turns out to be coolant, you have a leaking heater core. Another way to check if your heater core is leaking is to disconnect both of those hoses going through the firewall, plug one of them off and connect the other to an air compressor (don't over-pressurize, 25 lbs is usually plenty) and see if you hear any hissing noise and/or if coolant leaking out of that condensation hose. If so, you have a heater core leak. If not, you've ruled out one common source of cooling system leak/failure.

Jim2 · Oct 5, 2019

adsm08 said:
Heater bypass valve. Common failure item.

Thank you! Knowing what it's called made it easy to find.

While I'm waiting for the part to come in; can I just connect the two hoses (on the right) together, and bypass the whole thing for now?

...I'm not sure what effect that will have on the other hose that runs over to the intake.

Losing coolant, not burning

LittleJohn

New Member

adsm08

Senior Master Grease Monkey

Mark_88

Well-Known Member

tomw

Well-Known Member

BarnesAM

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Jim2

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