Trying to avoid a new radiator - at least until the end of the month.
2005 Jeep Liberty Renegade. The overflow reservoir is part of the pressurized system.
I’ve been losing coolant so I checked my radiator cap. Lots of give in the spring but they’re cheap and I replace it. But I’m used to having to apply a bit of force to compress the spring when putting the radiator cap on. The new cap requires no force , just line up and twist but I checked the spring and it is just like other new radiator caps I’ve gotten. But this cap goes on the reservoir so maybe that’s the difference? Still losing coolant at the same rate as before when I drive. No OBVIOUS radiator leaks.
Now for the weird part. When I am driving on surface streets the temp does not go up even at stops. But after about 45 minutes of my commute if I hit stop and go meaning cannot maintain 20mph, the temp will start to go up. Well that’s obviously low fluid right? So the first time I pull over and in the dark start to open the radiator/reservoir cap and get sprayed with hot coolant? WTF? I thought it would be empty. So I wait like 10 minutes until the temp lowers slightly and get onto surface streets. No issues even at stop signs/light.
Now for today and even weirder. I filled the reservoir with coolant last night and drove approx 60 miles home. Same symptoms as above but wait there’s more. Today the heater didn’t work. Like at all. So that means no coolant in the heater core right? But that means I lost a ton of coolant last night on my commute but if so that means my radiator was drained dry during my drive since the Jeep wasn’t sitting in a puddle this morning. OK the weirder part. I get heat if my car is going 60mph or more. Speed up to 60+ and wonderful heat but below that gives me slightly warmer than ambient air. My first instinct was that it was radiator fan related but car heaters don’t work that way right? And while that may explain the overtemp under unique conditions there is still the coolant issue.
At lunch I’ll go check the level and refill as necessary and give an update.
Just possibly a bad thermostat - some of this is a little outside the usual effects but allowing for some observer error it could be.
Pressure-test the cap (most auto parts stores have a tool), and if the thermostat isn’t too difficult to access, replace it. Cheap steps that should be done anyway before getting into deeper stuff.
Check your oil while your at it … you’ll be looking for a mysterious brownish white gelatinous substance on the dip stick … here’s an image …
If the oil looks like oil … then next conduct an exhaustive visual search of the entire cooling system … if the coolant is leaking out there should be an accumulation of salts where the coolant evaporated off the engine, rusty spots or even the green antifreeze itself bubbling out … you’ve said there’s no puddle of coolant under the Jeep if it’s just sitting … try looking after it’s been running a while …
Still nothing … then most likely the coolant is getting into the combustion chambers and going out your tailpipe … this may not be clearly noticeable in engine performance … but there’s really no other place for the coolant to go … I believe a mechanic would have a way to test for excessive moisture in your exhaust …
As far as your heater, best I can offer is your cooling system needs to be purged … depending of the engine, just filling the radiator doesn’t mean you’re filling the entire system … there may be an air pocket at the top of the coolant jackets … any decent maintenance manual will describe how to do this purge on your specific vehicle …
Update. No coolant in the reservoir but was coolant in the system and I tested the radiator cap. There is absolutely no force needed to put it all the way down on the reservoir so that is what I’m going to replace first since it is clearly not making a tight seal.
There looked like a little coolant under the radiator and I’ve seen that once before but only at work. Nowhere else.
I get that bad coolant flow may affect heat but it is not air pockets. So let’s put this on the table, would a bad water pump cause a leak. IIRC yes but can someone confirm?
Depending on design, a bad water pump can leak externally or internally to oil passages, or lose pumping ability if the impeller is corroded or comes loose on the shaft. It’s possible the shaft binds to the impeller only when hot or cold, but not the other way around, producing the odd fluctuations.
It’s a distinct possibility as the culprit, but I’d work through the cheaper stuff first, as it’s always a good idea to do that stuff along with a pump anyway.
The weak cap is very suspicious, too. Start there and have the store test the new cap before you walk out with it.
This is most likely it. It fits the symptoms and Gary T is a professional.
When your engine and vehicle are going fast the water pump moves just enough coolant to flow through the heater core and supply heat. Slow speeds, no heat and coolant boiling off and being discharged out the over-flow. Sometimes no heater due to low fluid.
Nobody likes to hear it is a water pump replacement, but cheer up, if it has a timing belt you get to replace that too while you have the water pump off. You might have a chain, depends on which engine you have in your Jeep.
And you may have air pockets in the system now since you have been losing and replacing fluid often and that may confuse the diagnosis. Continue to explore but I also think that your water pump is not moving enough fluid.
The reservoir (more properly called a surge tank) is part of the system. ETA: The entire pressurized portion of the cooling system needs to be filled with liquid and no air.
Yes, a water pump can leak coolant. Try to find the weep hole and see if it’s wet or stained. This is independent of whether or not the pump has other problems.
Believe me, when I saw Gary T’s post I started pricing out a new pump and seeing if I could do it myself. Looks like I need a new water pump before it seizes.
I’ve worked on some weird engines and seem to remember at least one case where the water pump formed part of the crankcase seal itself. I could be wrong and confusing something more like what you’re describing.
It almost sounds like your replacement cap does not have a deep enough spring on it. I would double check the part number with the parts dept and make sure you have the right cap. If the wrong cap was the culprit and you blew out most of your water you will need to bleed the system, just letting it idle for some time with the cap off until it is good and hot is usually enough to bleed it properly. If you don’t bleed it it will continue to overheat and blow coolant out.
The easy (not necessarily correct) bleed. Open the radiator while the car is running. Bounce the front bumper a few times. Top off. Lather rinse repeat.
Obviously if you have a bleeder you want to open it but if not just keep topping off while hot until it stays full has worked for me. I do admit my automotive experience has been limited since the 80’s when I switched to big rig diesels but I did continue to work some with small trucks in our fleets.
I never heard of this either until my VW GTI started overheating. The pump forms part of the seal. Was a hellava thing to change too, what with a transverse engine.
So far as the radiator cap, on some aftermarket radiators, the “factory specification” radiator cap will not work properly!
This is due to cheap products being made these days by manufacturers who don’t bother to check or get the product specifications correct. Also they could care less!
Anyway try different radiator caps and see what works best. Read about how a radiator cap should work and be sure yours is doing what it should.
If you know for sure the radiator is original factory equipment (and not an aftermarket replacement) then try getting a radiator cap at an auto parts store by telling them the manufacturer, year, and model of your vehicle.
Or if that is not the right cap, go to the parts department of a dealer of your manufacturer of your vehicle.
Next if still having overheating problem, verify your dash temperature gauge is the correct temperature by using a thermometer, be sure the fan is working - replace the thermostat. Do not install it upside down!
Is the radiator fan kicking in when the engine gets up to temperature? If you’ve got a coolant leak combined with no fan you’ll get the symptoms described. Driving along at a reasonable clip will force enough air over the rad, but it’ll soon overheat at low speeds. This will raise the coolant system pressure and make the leak worse.
