What's going on with my cooling system!?
01-08-2024, 09:30 PM
#1
Intermediate
Thread Starter
What's going on with my cooling system!?
So confused as to what's going on and need some of you seasoned vets to chime in.
A few weeks back I noticed my coolant level was drastically low, but never had any noticeable increase in engine temp. I topped off the coolant, and later that day once I parked I noticed coolant pretty much spilling on the ground from under the expansion tank. Again topped off the coolant and carried on, and all seemed well. Fast forward to last weekend, I notice my temps getting up to 220 (I'm usually right at 180). I open the expansion tank and boom, brown milky sludge on the cap. Awesome! Fearing the worst, I do the head gasket check with the blue fluid and breather tool. After all, there was no coolant or water on the dip stick or oil cap so I didn't suspect coolant entering the oil. Thankfully it didn't detect any engine fumes so the head gasket seemed fine; this left me thinking it must be the oil cooler. So I topped off the coolant again, but this time I also added a quart of oil. About 30 minutes into my trip this weekend, the coolant temp starts shooting up and this time almost maxes out. Luckily I was able to pull off the road right as I got my first red "coolant too hot" alert on the dash. I let her cool down, and she has been fine since.
For some reason when the coolant is full, my system spews it out and almost overheats. When the coolant is low, the vehicle seems to operate fine. I already ordered a new oil cooler and expansion tank to replace as precautionary measures, but is this as simple as a faulty expansion tank? Why when the coolant is full is it getting spit out and then temps go nuts? My only explanation is that a leak in the oil cooler or expansion tank is causing the coolant to boil faster, and then it spills out the overflow/pressure valve. Plus the time it ran the hottest was the only time I simultaneously added oil (and thereby increased oil pressure). But this also doesn't explain why the engine seems to run cooler with less coolant. WTF is going on!?
A few weeks back I noticed my coolant level was drastically low, but never had any noticeable increase in engine temp. I topped off the coolant, and later that day once I parked I noticed coolant pretty much spilling on the ground from under the expansion tank. Again topped off the coolant and carried on, and all seemed well. Fast forward to last weekend, I notice my temps getting up to 220 (I'm usually right at 180). I open the expansion tank and boom, brown milky sludge on the cap. Awesome! Fearing the worst, I do the head gasket check with the blue fluid and breather tool. After all, there was no coolant or water on the dip stick or oil cap so I didn't suspect coolant entering the oil. Thankfully it didn't detect any engine fumes so the head gasket seemed fine; this left me thinking it must be the oil cooler. So I topped off the coolant again, but this time I also added a quart of oil. About 30 minutes into my trip this weekend, the coolant temp starts shooting up and this time almost maxes out. Luckily I was able to pull off the road right as I got my first red "coolant too hot" alert on the dash. I let her cool down, and she has been fine since.
For some reason when the coolant is full, my system spews it out and almost overheats. When the coolant is low, the vehicle seems to operate fine. I already ordered a new oil cooler and expansion tank to replace as precautionary measures, but is this as simple as a faulty expansion tank? Why when the coolant is full is it getting spit out and then temps go nuts? My only explanation is that a leak in the oil cooler or expansion tank is causing the coolant to boil faster, and then it spills out the overflow/pressure valve. Plus the time it ran the hottest was the only time I simultaneously added oil (and thereby increased oil pressure). But this also doesn't explain why the engine seems to run cooler with less coolant. WTF is going on!?
01-09-2024, 12:44 AM
#2
Racer
I’m not sure why the engine is running cooler with less coolant in the system… but your thought about the lack of pressure causing an overheat is a good guess. The cooling system is pressurized by the cap on the expansion tank. If the tank is leaking badly then the system won’t hold pressure and the boiling point is lowered. The oil cooler is also a known weak link, but I would guess the overheating is the expansion tank. Which oil cooler did you buy? I’ve read the aftermarket nissens brand is supposedly a better design than the original.
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Petza914 (01-09-2024)
01-09-2024, 12:50 AM
#3
Intermediate
Thread Starter
I’m not sure why the engine is running cooler with less coolant in the system… but your thought about the lack of pressure causing an overheat is a good guess. The cooling system is pressurized by the cap on the expansion tank. If the tank is leaking badly then the system won’t hold pressure and the boiling point is lowered. The oil cooler is also a known weak link, but I would guess the overheating is the expansion tank. Which oil cooler did you buy? I’ve read the aftermarket nissens brand is supposedly a better design than the original.
Yep I got the Nissens one. FCP has both an oil cooler kit and expansion tank kit which makes it easy and convenient.
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BobcatBrian (01-09-2024)
01-09-2024, 01:20 AM
#4
Racer
I guess it could be as simple as a faulty cap, but with sludge in the coolant, it’s almost certainly a leak at the oil cooler. Just puzzled quite honestly.
Yep I got the Nissens one. FCP has both an oil cooler kit and expansion tank kit which makes it easy and convenient.
Yep I got the Nissens one. FCP has both an oil cooler kit and expansion tank kit which makes it easy and convenient.
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blaino (01-09-2024)
02-20-2024, 06:40 PM
#6
Intermediate
Thread Starter
Just circling back here as I solved the problem. It ended up being the oil cooler.
First I swapped out the coolant expansion tank, but the symptoms remained (above-average temps (220+) when driving over 2,000 rpm). Drained the coolant, drained the oil, then replaced the oil cooler with a new one (Nissens one mentioned above). Symptoms gone and back to normal.
As I suspected, both air and oil must have gotten into the coolant system through the oil cooler, thereby contaminating the coolant with both. The air then caused the coolant to boil faster, so the more full the system, the more coolant would spill out of the expansion tank. This only worsened when I added more oil which increased the pressure in both systems causing both temps to go haywire.
@Dilberto's oil cooler instructions helped, but I would add a pretty significant clarifier that it is NOT necessary to remove the band clamps on the oil cooler coolant lines prior to disconnecting the oil cooler from its bracket. This would have saved me (and anyone else who does this) a tremendous amount of time wrestling with the damn clamps with only inches of space to work with.
First I swapped out the coolant expansion tank, but the symptoms remained (above-average temps (220+) when driving over 2,000 rpm). Drained the coolant, drained the oil, then replaced the oil cooler with a new one (Nissens one mentioned above). Symptoms gone and back to normal.
As I suspected, both air and oil must have gotten into the coolant system through the oil cooler, thereby contaminating the coolant with both. The air then caused the coolant to boil faster, so the more full the system, the more coolant would spill out of the expansion tank. This only worsened when I added more oil which increased the pressure in both systems causing both temps to go haywire.
@Dilberto's oil cooler instructions helped, but I would add a pretty significant clarifier that it is NOT necessary to remove the band clamps on the oil cooler coolant lines prior to disconnecting the oil cooler from its bracket. This would have saved me (and anyone else who does this) a tremendous amount of time wrestling with the damn clamps with only inches of space to work with.