Hi Scotty, I'm a long time fan of your Youtube videos - hence me arriving here.
I own a 1991 built Mercedes Benz 190e 1.8 with about 95,000 miles on the clock. I'm not sure if the 1.8 M201 engine made it to the USA as it's the smallest four pot model. Mine is the very basic Australian version - so doesn't have a lot of fancy electric options to go wrong and is very reliable. My one over-riding niggle is no heat coming through the vents. A bit of a bugger in the UK at this time of year. The line into the heater matrix is warm. The line out is cold. The rest of the cooling system runs as normal, nowhere near over-heating.
Obviously the matrix / core is plugged.
I tried a whole cooling system flush with a flushing product by Prestone. As the car is relatively new to me it seemed a good place to start. To be fair, the initial drain and flush with a hosepipe didn't look promising as the old coolant came out clean and pink from the getgo. The previous owner (who had it for a long time) was using Mannol G12+ which is a pre-mixed coolant that other Mercedes owners seem to recommend. The engine block is aluminium, as is the main radiator, so there was none of the usual brown rusty muck in evidence. Anyhow, I ran the engine at idle for the full recommended hour with the heater fan on and settings at full heat. Made no difference really, perhaps a little cleaner. Heater is still putting out cold air.
I've decided to isolate the heater system so I can make a determined effort to flush it. My thinking being to loop the system though a pump sitting in a bucket of flushing solution and let it run for a few hours from the inlet side and then reverse it and so on until it runs clean (hopefully). I had a forage on YouTube to see what people were using to flush out really clogged cores, and kept coming back with CLR. Indeed, I've seen you unclog out a heater matrix using this stuff with success. HOWEVER, I'm told on forums this stuff is quite corrosive and reacts with aluminium radiators and heater cores. That said, nobody addresses this on YouTube how to videos. The Mercedes 190e has the matrix hidden right under the dash and is a few days work to remove and replace. Currently, I have no leaks in the cooling system and I can live with wearing a coat in the car for winter. The last thing I need is to introduce another problem by causing the core / matrix to weep into the cabin due to corrosion. So, long ramble short ... will CLR eat my heater core? Can it be diluted to a safe level whilst being effective?
Cheers in advance.
Obviously the matrix / core is plugged.
Either that or you have a blend door not working properly, which would be no surprise after 34 years. Check to see if both heater hoses are hot, which indicates coolant is flowing through the heater core. I would not use CLR in your cooling system since it may well cause corrosion problems.
You might have success reverse-flushing your heater core with a garden hose, at least if you get a day when the temperature is above freezing and it's feasible to do. I did that when the heater in my 1999 Jeep Cherokee stopped working and it pushed out a bunch of gunk. Heater worked great afterwards. Of course you need to avoid using excess pressure, and take into consideration that if your heater core is weak reverse flushing it might cause it to leak. (However if that were to happen the heater core would have started leaking on its own in due course anyway. This is just part of the risk one takes driving and servicing a decades-old vehicle.)
@chucktobias I had another go at flushing the heater core in isolation. I bought a proper flushing gun with a multiple stepped nozzle arrangement for universal pipe fitment. I didn't use the air -pressure facility, just the mains pressure garden hose feed. It runs at about 45 psi. Much to my surprise, the flow through the matrix via both outlet and inlet was strong and clean, with no signs of debris. I reconnected the core hoses to the system, topped up the coolant fluid, and ran the engine until the thermostat kicked in at about 87 C. Still running cold air through the side vents. I checked the vacuum operated temperature control valve immediately inline with the core. It's working correctly - opening fully on the full heat setting, closing fully on cold, and opens incrementally on intermediate heat setting.
HOWEVER, the pipe directly off the temperature valve going back to the water pump never gets more than lukewarm - probably from the heat of the exhaust below it.
I'm at a loss to explain why I have a fully flowing core but not getting heat.
Thermostat is brand new.
Does your 190 have a heater control valve and is it working properly? US models 190e 2.4 had them (Many older cars had them, newer ones don't).The line into the heater matrix is warm. The line out is cold.
You're flushing with a corrosive product and you will risk creating a leak. Rust will be removed and that rust often what's preventing the core from leaking right now.The last thing I need is to introduce another problem by causing the core / matrix to weep into the cabin due to corrosion.
Here's " THE VIDEO ", Scotty doesn't dilute it. Diluting the CLR wouldn't necessarily reduce your chances of creating a leak. Using too much pressure (air or water) when flushing often does cause leaks.will CLR eat my heater core? Can it be diluted to a safe level whilst being effective?
Try flushing only the core and nothing else with water as a first step. Then decide if you want to take further steps.
@hixster Yes, I have the vacuum operated heat control valve and it's working as expected. Fully open on full heat setting. Fully closed on cold setting. Proportionally opens according to heat settings through the range.
Flow through the core was rechecked today, and it is strong in either direction - and clean. However, the pipe immediately in front of the temperature control valve (traces back to the radiator pipe on the return side) never gets more than lukewarm, and that from being over the exhaust manifold.
I'm running out of ideas now.
Im at a loss to explain why I have a fully flowing core but not getting hot.
If your heater core is getting hot but the hot air is not reaching the interior of the car the only thing left is a problem with the flaps or ductwork in the dashboard.
@chucktobias Flow in either direction (garden hose at 45psi) is strong and clear through the core. However, only one side is getting hot. The pipe on the temperature control valve gets tepid at best. However, the valve works as it should via vacuum operated switches. All the flaps seem to be working as expected. If it weren't for the running temperature being a constant 85 C and never getting anywhere near the red zone, despite enthusiastic driving, I'd suspect the water pump - despite there being no leaks or squeals. The system has been well burped of air.
There's not a whole lot of options left. Try bypassing the temperature control valve and hook the heater core up directly to the water pump. (If the pump were bad the engine would overheat.)
@chucktobias Weirdly it seems the core flush did the trick. Heater chucked out decent heat when the car was in motion. I guess sitting on the drive idling until the thermostat kicked in wasn't quite enough
