No heat anymore, car doesn't come up to temp while driving.

[ScHpAnKy]

Swapped my thermostat yesterday since I figured that was my problem, the car does now come up to temperature while idling but after a minute or two of driving it drops to just above the blue marks on my cluster.

Emptied and bled the whole system for a few hours to the point that when I get back home after a 40min drive there's a quick "pfft" noise when I crack the bleeder screw, but that may be a result of the the thermostat not opening due to it never reaching operating temp while driving.

The other thing, I have like no heat in the car - it's KINDA warm while idling, but freezing cold while driving. Radiator doesn't appear to have leaks, I'm able to push water through the heatercore.

The only things I've done as far as customizing the cooling system is deleting the check valve for the heatercore (since I always want it running through it)
and deleted the Throttle body heater lines (runs back to the block.)


I should also note that this was the same issue I had in the summer, but with the weather being in the mid-thirties lately it's been considerably worse!

[bmw325csi]

I want to say, defective thermostat

[Jand3rson]

Stupid question, but are your coolant lines at the firewall hooked up correctly?

[e30slidewayz]

Did you install a lower temp thermostat? Also, the heater core may need flushing or replacement... that things a bitch to mess with though. That is if there hasn't been any recent refitment of hoses, etc of course.

[ScHpAnKy]

I want to say, defective thermostat

I'd believe that if it wasn't my third time replacing it :(
Added to that, the top hose gets HOT around halfway (idling.)

Stupid question, but are your coolant lines at the firewall hooked up correctly?

yup, I've had heat before, about mid-summer, then one day this started happening... swapped to new thermostat #2 and continued... finally got the balls to swap in a third in fear that the replacement was bad... still the same result.

I have a feeling there's an air pocket somewhere, but I've followed the correct bleed/fill procedure like 20 times now, including tricks like filling the top hose first.

Until then, I can overheat in heavy traffic but otherwise my temp gauge is about 1/4.

Did you install a lower temp thermostat? Also, the heater core may need flushing or replacement... that things a bitch to mess with though. That is if there hasn't been any recent refitment of hoses, etc of course.

same temp I think (180F / 82C) - I've already flushed the heatercore, though. ughh any idea what the hoses running into it should be for temp? I can't get my hands on them while running, but I can probably get my IR temp gun in there.

[blackhawkimpact]

Clogged radiator?

[butters]

Clogged radiator would cause overheating not underheating.

At this point I would be checking the thermostat(s) on the bench/stove to confirm functionality.

Are you putting a hole in the thermostat like some sources suggest?

Maybe there is a defect in the head that is not allowing the thermostat to seal internally? Thus "leaking" out into the radiator all the time and only getting warm/hot when you heatsoak it at idle.

I feel for you with this frustration, hope you find the cause!

[M-technik-3]

Did you check the thermostat in a pot with a gauge in the pot.

[ScHpAnKy]

Did you check the thermostat in a pot with a gauge in the pot.

yup, even the one I just took out functions normally

[M-technik-3]

the one you took out does it have a small pilot hole to help bleed the head? If not consider drilling one. Bleed car on an up hill slope too?

[ScHpAnKy]

the one you took out does it have a small pilot hole to help bleed the head? If not consider drilling one. Bleed car on an up hill slope too?

nope, all three don't - but I'm fairly certain I can rule that out as it should only assist with getting the thermostat flowing to the top hose, aye? I don't have a problem there, it's all sorts of hot and fluidy

I always bleed my cars on jackstands with enough space under the front valence for an industrial size plastic tub... so 1.5ft off the ground? I haven't had an issue with my M20 / M42 cars... just this one :(

[M-technik-3]

You have an IR thermo gun? Wondering if something is clogged.

[ScHpAnKy]

You have an IR thermo gun? Wondering if something is clogged.

IR gun reports ~180 pretty much everywhere, including top hose and radiator.
I've been bleeding it with the radiator cap off and watching for overflow, filling up what it lost and continue to have the same problem as before. I still have no heat... and at a total loss.

Some observations since I've posted last:

- There's no oil in my coolant

- when I go hard on the gas while driving now the temp will creep into the red if I'm not careful, the second I get off the throttle it begins to fall back down to 1/4

- if I just drive normally, around town, sitting in traffic, the car will run 90% of the time at the 1/4 mark and halfway if it's slow traffic. If it's just sitting in one spot for 10-15min, it'll eventually climb into the red, regardless of the electric fan.

- There is always steam to be relieved in the system, after all the fill/bleeds I've done (12+) every time the car gets anywhere over the halfway mark it'll bleed steam out of the bleeder screw until the car cools down

wtf am I doing wrong?

[butters]

-when I go hard on the gas while driving now the temp will creep into the red if I'm not careful, the second I get off the throttle it begins to fall back down to 1/4

how confident are you in the coolant temp sensor? I'm not sure how this is physically possible.

I realize it would not explain the lack of heat but it seems like what you're seeing on the gauge is perhaps not accurate. when the IR gun reads 180 all over, what's the gauge saying? I've found that the standard brown sensor in my S50 head combined with the cluster gauge is wonderfully accurate, showing a little cooler in winter and moving around the halfway mark as I cruise, hit traffic, ambient temp changes, etc. as compared with more modern cars "buffering" the signal.

[328ijunkie]

Triple check your Hcore hoses. Sounds like theyre backwards for one. For two it sounds like your HG may be leaking.