I recently did a coolant flush on two of my vehicles. Neither have been the same since and both run rough in cold weather. Any thoughts?

is there cardboard in the radiator slot any CEL codes

Not sure I understand the question, but no, there are no codes. Took it to dealership after talking with a couple mechanics who didn't seem to know what to look for and dealer says its fine, no leaks etc. Wondering if I might have ruined the ECT sensors during the flushes (possibly on both vehicles) due to improper bleeding. Ideas?

I have taken this from the Hyundai forums, posted by canderson, and taken right from the Hyundai Manufacturing site: Please note the warning in the fourth paragraph,(don't personally know if your model is the same layout as this, but if so, you possibly could have gotten some anti freeze into the relays or electrical), then the bleeding procedure. Obviously the heating/bleeding will take some time because it must be done with the radiator cap off since you cannot remove it while hot & under pressure. From your friends at hmaservice.com (DO get yourself a 'membership' there - it's free) ... the better instructions are shown on the 2008 model, but same design. There's a bit of Korean/English going on, but the intent always seems clear at their site. [b]Engine Coolant Refilling And Bleeding Never remove the radiator cap when the engine is hot. Serious scalding could be caused by hot fluid under high pressure escaping from the radiator. When pouring engine coolant, be sure to shut the relay box lid and not to let coolant spill on the electrical parts or the paint. If any coolant spills, rinse it off immediately. 1. Make sure the engine and radiator are cool to the touch. 2. Remove radiator cap. 3. Loosen the drain plug, and drain the coolant. 4. Tighten the radiator drain plug securely. 5. Remove, drain and reinstall the reservoir. Fill the tank halfway to the MAX mark with water, then up to the MAX mark with antifreeze. 6. Fill fluid mixture with coolant and water(4 : 6) slowly through the radiator cap. Push the upper/lower hoses of the radiator so as bleed air easily. • Use only genuine antifreeze/coolant. • For best corrosion protection, the coolant concentration must be maintained year-round at 50% minimum.Coolant concentrations less than 50% may not provide sufficient protection against corrosion or freezing. • Coolant concentrations greater then 60% will impair cooling efficiency and are not recommended. • Do not mix different brands of antifreeze/coolants. • Do not use additional rust inhibitors or antirust products; they may not be compatible with the coolant. 7. Start the engine and run coolant circulates. When the cooling fan operates and coolant circulates, refill coolant through the radiator cap. 8. Repeat 7 until the cooling fan 3 ~ 5 times and bleed air sufficiently out of the cooling system. 9. Install the radiator cap and fill the reservoir tank to the "MAX" line with coolant. 10. Run the vehicle under idle until the cooling fan operates 2 ~ 3 times. 11. Stop the engine and wait coolant gets cool. 12. Repeat 6 to 11 until the coolant level doesn't fall any more, bleed air out of the cooling system. As it is to bleed air out to the cooling system and refill coolant when coolant gets cool completely, recheck the coolant level in the reservoir tank for 2 ~ 3 days after replacing coolant.

All you accomplished is draining and refilling radiator only, you added clean coolant to dirty coolant by not draining the engine block. You need to drain coolant from engine block.

Good advice I've just bought a 05 hyundai tucson and I've been having a few problems with the heating system problem is it has a 08 santa fe radiator which has no radiator cap and is only filled through resoviour and last owner now tells me he had new pump fitted and filled the system again and had problems bleeding system and has left the thermostat out to let system circulate so I'm going to have re install thermostat and start from scratch how do I bleed the system using reservoir only how do I do it.. Thanks

every car has to have its thermostat installed. whether in a warm, hot climate or cold. The thermostat brings the trans fluid up to temperature to shift and operate the tranny properly. Notwithstanding keeping you warm. Also, the only way water cools is to let it sit in the radiator, thanks to the thermonstat, even for a minute to allow the it cool, so when stat opens, cool water enters the block, otherwise you keep circulating very hot water. Never had a need burping any coolant system. But most times I fill thru the radiator neck, thermostat removed. Replace stat and add anti freeze as necessary. This ensures block is full of clean anti freeze. This method routes the antifreeze into the block, out the lower hose up into the radiator and out the top radiator hose. Or you can buy a Prestone BAckflush kit. Install as directed. This will reverse flush block, heater core and radiator. Just be sure which is in hose and out hose.

Thanks that's great advice I've also noticed biue smoke when I cold start strong smell inside would this be glow plugs or blocked jets would it be mechanic only job or could it be done DIY any advice.. Thanks