Temp guage runs in the red! 93 mark VIII 135K miles

have a radiator shop check for blocked cores
have a compression test done
water pump not an issue unless you have removed the ac compressor out of the system and now the water pump is being driven in reverse because an idle pulley was not used in place of the compressor

You need to find an honest Joe!! My first thought is get the rad checked. Any good mech would know how. It should be hot at the top half and cooler below, but even spread across the whole rad. You don't say if its forcing water from the header tank? If it is then its possible a head gasket has gone. If its been maintained but the coolant hasn't been flushed and replaced every 2 years then its likely the main rad is partially blocked. There is no ready cure for this despite a lot of additives and theories, the only sure way is to replace the rad. Is there no good DIY neighbour who could help? I understand your fears about some dealers but if in doubt take your DIY neighbour with you so they will behave.

Check belts driving the water pump otherwise the pump is seized or the circuit has a split check if you are using any water up..

air lock in the cooling system get a plastic bottle cut the bottom off turn upside down put on radiator filler and run engine cut full off water wait until all air bubbles stop then remove and put cap on see how that goes

first, is/was the temp guage showing over heating? If so you should have checked/ replaced the fan temperature switch on the radiator ( or follow the fan wiring to it's location) depending on air temp, and driving conditions, the motor may not need the fan. If it's not, cover the rad with something{paper,plastic} until the guage begins to show overheat condition, then the fan should start. # DO NOT LET IT GET INTO THE RED ZONE! If you keep the reservoir closed, the radiator will **** up the coolant after warming/running, and a cool down.

it's overheating, for sure,
is coolant levels dropping? cold checked at rad cap?
"pulled over and found a hose to cool the radiator and hose near the thermostat,"
i can not understand this statement"above"
if it overheat only parked, check fan for full ops.
if overheats moving too, wont stay cool moving fast
then:
bad rad cap
bad thermostat , they have 7 year life says STANT. (and why)
belts slipping (to water pump)
rad cores blocked (IR thermo gun it) ask
water pump impellers rust 1/2 gone?

all this assumes no coolant loss, if you have loss, tell where.,
where it leans
ground
passengers toes (foot well)
engine oil pan? milky oil
if A/T TRANS, check it for milky too.

Have you tried running car from cold, with rad cap off, & heater turned on, coolant topped up, an inch or 2 from top of rad? Let it run up to operating temperature, cooling fans kick in & out 2 or 3 times, and top up coolant as needed, then put rad cap back on, & fill return bottle up to mark. There may be a worse problem, but bleeding system as I have described, ensures all air out of heater core & cooling system, which has been cause many times before on all makes & models of vehicles. Especially when no heat situation. Let me know if it helps.

you cylinder head is cracked, or your head gasket is gone. there is a test a shop can do on the cooling sytem to see if this is so

it sounds like an air pocket... try squeezing the rad hoses a few times and keeping an eye on the level in the rad... this is probably best done with the rad cap off... of course make sure it is cold before you remove the radiator cap.

Robert

How is the problem with your mark? Has it been resolved? Is it physically overheating or does it just look like its hot? Have you swapped the sending unit for the coolant temp gauge?