Hi guys I just got a 94 suburban. 5.7 l its not heating that great. All fluids topped off no leaks what could be causing this at lower speeds not that warm at higher speed lil better but still not hot.

 

Could be a partially clogged heater core. What's the coolant temp. when truck is fully warmed up? If not up around 180*F or better, might be a bad t-stat.

 

Thanks how do I check the temp or um log the heater core

 

Touch both heater hoses. Be careful not to get burned. If both of them are equally hot, then the heater core is not clogged. If one of the hoses is cooler than the other one, then the heater core is clogged or partially clogged. You can put a mechanical temp gauge on the truck temporarily to check the temp.

 

I take it that your gauge cluster doesn't include a temp gauge or it doesn't work?

If clogged, might as well R&R it.

 

The cluster shows the temp 100 210 260 it goes from around 160 to 210

 

OK checked the hoses the upper one is hot lower one is cool

 

i cant really use water to push anything through and i dont have a air compressor any ideas?

 

I'd advise replacing the heater core cuz even if you could unclog it, it's 18 years old and will probably start leaking soon anyway.

If that's not on the agenda, then try using one of Prestone super duper radiator flushes. Since you apparently have some flow, it might open it up.

Edit: Is there a water control valve in one of the heater hoses?

 

I had to use an air compressor to unclog mine which was completely clogged. Try and borrow one from a friend or possibly rent one.