HEATER Does not get hot only slightly warm Recently solved a overheating problem(Blocked RAD) Part of diagnostic was to remove Thermostat, this as replaced later I am assuming there is now air in the system. I have beld TOP by removing the hexagonal plug TOP of RAD running engine and topping up coolant. All TOP hoses feel hot, I have never worked on heater hoses dont know where they are or how to bleed them, I cannot get a hose pipe to back fill them as I live in First floor apartment and dont know if they are HOT as I dont know where they actualy are. Confident it is not Heaer Matrix as prior to overheating prob heater worked find and even now cold sie makes heater really cold and HOT side makes it slightly warm so heater working. Is it likely it is the new Thermostat? This is a PIG of a job on this engine to replace but if needs must. Think I have covered all bases here. Thanks Stuart

check the coolant pump is good and the radiator is not blocked both air flow thru the core and coolant flow thru water tubes, you can check for coolant flow thru the rad by feeling the core for any cold spots after running engine til warm then switch. off the radiator should be hot at top and cooler has you feel down with even temp all along any cold spot means the rad is partialy blocked.if the rad is red hot at top and cold at bottom it may be the pump if its got a electric cooling fan check thats working ok, good luck

Sounds like a thermostat is being sticky. A water pump issue should cause the vehicle to over heat quickly while driving if it is not pumping.

Have you considered power flushing the block to remove buildup of oxidation which insulates and holds heat? I assume you have replaced the thermostat with no results. There are opinions about operating with not thermostat. Some say it prevents the engine from reaching operating temperature and therefore is running ineffectually and won't meet emissions.

1) Your car should have a thermostat regardless of what your mechanic says. Fuel injected vehicles run better and more efficient at proper temperatures. So re-install thermostat properly before step 2.
2) Did the mechanic make sure the heater was on high temperature and blower on when he re-filled the cooling system?
Maybe not. So start engine when cool and rad cap off. Fill rad about an inch from the top and let the engine run up to normal operating temperature and keep an eye on coolant level in rad and keep it topped up as it's running. Rev the engine slightly for 5 seconds or so every once in a while to help with flow and pressure to make sure coolant is getting to and through heater core. Keep observing flow in rad to make sure it's good, when thermostat opens. You won't see much movement until thermostat opens at normal operating temperature, then you should see flow in rad and shortly after, rad fan should come on.Leave rad cap off and heater on until the rad fan comes on and off 3 or 4 times to make sure all air is out of the system. Then, make sure rad is topped up, put rad cap back on and fill return bottle to proper level. If that doesn't cure your overheating, then something was done wrong, or you have a possible head gasket problem but proper diagnosis should be done by a competent mechanic. What was the car doing initially to warrant these repairs, overheating?

Coolant system have bleed points. There is air in your system that needs to be purged out through the purge valves.. There maybe a few. You have to slightly open them when you first fill the system and let the coolant circulate till a little bit of coolant comes from bleed valves then you close them. Letting the system purge air by leaving the radiator cap open is not enough. Are you sure you put the correct temperature thermostat in , and facing the correct way?

could be waterpump?
i was going to say rad fan,but if so heater would be hot.
lack of coolant will make heater core to blow cold,if engine heats up with full coolant,usually means poor or no circulation.
water pump?
run engine with full coolant,at operating temp.with rad cap off and look in rad cap hole and see if there is movement of water inside rad.
[rad fan will not come on if water is not circulating through rad water pump?]

First of all you need to check your coolant return bottle level, it's probably low, and needs coolant added. Heater will be starved for coolant, if level is low, thus, cool/cold air comes out. Try to add when engine is cool, to avoid getting sprayed with hot coolant. Leave cap off for a while, turn your heater on (not defrost) and let engine run up to temperature, and add more as needed while you watch level. Rev engine slightly and hold it for 5 seconds or so, every once in a while to help circulate coolant, and remove any air in system. If you have an actual rad cap, that you can remove and watch flow in radiator, that's even better, for adding and bleeding air out same way. Make sure your rad fan is working as well, and once you get it topped up, and heat back working, I'd seriously consider having a system pressure test done, as you obviously have a leak somewhere if the level went down to the point of overheating, and heater was starved for coolant. Keep an eye on that return bottle level until such time you have it checked, to avoid more damage to engine.

NORMALY THE HOT FLOW ENTERS THE TOP HOSE AND COOLER WATER LEAVE THE BOTTOM HOSE BACK TO THE BLOCK, SO IF THE TOP HOSE GETS WARM THEN THE RAD IS BLOCKED , IF NIETHER GETS WARM/HOT THEN THERMOSTAT NOT WORKING, OR YOU HAVE BLOCKAGE ELSE WHERE, SO REMOVE BOTH HOSES FLUSH RAD WITH HOSE PIPE, (WHEN ENGINE IS COLD) SEE IF WATER FLOWS OUT AT SAME SPEED AS U R FILLING IT, IF NOT ITS BLOCKED, 2ND REMOVE THERMOSTAT AND FLUSH ENGINE OUT, U CAN BUY RAD FLUSH/CLEANER AND TRY THAT,

Remove and raise upper hose at thermostat end and remove lower rad hose.
Fill rad with a hose and watch for flow from bottom rad hose and/ or bottom rad hose connecton.......water should fall though rad easily.
Honda rads are cheap.....any restriction....replace rad.

Remove thermostat....fill thermostat housing with hose and watch for water flow at bottom rad hose.
Flush good.

Remove heater hoses.......flush back and forth until a good flow is present "With heater control set to hot" if no or poor flow....replace heater core.

Stop leak can plug everything.

Also.......not likely causing over heating....but ....at your mileage,if you do not know if the timing belt has been changed.....CHANGE IT NOW!
Water pump is optional at this mileage.

what is heater tap you saying right name for it? if something is blocked the overflow bottlw wouldnt do anything here an idea to check u have 2 hoses running from the rad check if both are hot if not then rad is blocked or water pump is shot sometimes you can tell if water pump is shot is there is a hole near the spindle if it has antifreeze coming out even a little needs to be repaired replace actually more i think about iut you do have water pump prblem