Last year, I overheated while coming back from a car show. The coolant hose behind the engine, next to the master cylinder blew off as a consequence. I did the following:

Changed upper/lower hose as well as the busted one
Changed Stock radiator to KOYO
Installed E-fan with shroud
Changed Water Pump

Should I change the Thermostat since the original one is still installed (1987 TII with 169,000 miles)?

Should I look for and purchase the engine bay pan that goes at the bottom of the engine?

Is there anything else that can be done to maximize engine cooling?

 

I'm surprised that you didn't put in a new thermostat when you did all the other work.
Go ahead and do it now.

As for the bellypan...
You'll see endless advice about how critical this piece is.
In my experience- both highway and around town- it makes very little difference but I run it anyway (can't hurt).
I can almost guarantee though that if you're having cooling problems, installing that bellypan won't fix 'em.

 

Change your thermostat and that may help more than you think.

 

the engine undertray seems to matter more on cars with front mount intercoolers

 

put the belly pan on anyways.It prevents Debris from Flying onto the Front of the engine,So it will be cleaner.
The Air will be directed Better from the fan to the engine,instead of hitting the Engine and getting sucked out by the air under the car.

 

You could add water wetter to the system or run 100% water wetter + water or whatever they recommend but I imagine that would cost quite a bit.

 

Don't run 100% water. Water doesn't lubricate the water pump, and when the temperature falls, engine replacement will be the result.

 

Water WETTER, not water. You could just add more water to the water + coolant mixture though. Or run water wetter + coolant since I'm not sure water wetter has any freeze protection.

But now that I think about it, I'd make sure that the car didn't overheat as a result of the coolant hose bursting and not the other way around as your post indicates. It certainly makes more sense since I don't see those hoses failing unless maybe you reached 250*+. Its also very common for those hoses to fail.

Either way your cooling system should be under very little stress on the highway because of the airflow moving across the radiator. It should be rock solid at 195-200* and increase slightly as you apply more load and increase engine speed. If you were cruising on the highway there had to have been a failure that caused the engine to overheat.

The bellypan helps mainly on the highway though so it may be a good idea to buy one. Its important to understand that it will probably not change your water temp since the thermostat will open less now that your cooling system capacity has increased. Really the best tool for monitoring water temps IMO is a real gauge, VDO has cheap accurate ones.

 

My car most likely overheated due to a clogged OEM radiator and failing water pump. The hose burst as a consequence since it was already deteriorated from oil seeping from the oil filter housing. Should I get the OEM thermostat or will any after-market do?

As far as the belly pan, it's best to side on the side of caution and probably install one anyways. Any good place to find one of these?

I have no idea what water wetter is, as posted above. Can someone explain?

 

It doesn't have any effect (or a tiny one) on the freezing point of the liquid. Running 100% water w/ or w/out the additive also means a reduced boiling point, which is of less concern due to the increased pressures in your cooling system. And the question of whether water wetter does anything at all to reduce temperatures is out there, as well. Do a google search and you'll find some negative reviews.

Buy an OEM thermostat. Some of the ones available in your average parts store do not open at the proper temperature.

eBay or the classified section will likely be your best bet for finding a belly pan.

And water wetter is an additive that claims to reduce coolant temperatures by as much as 30 degrees, provide rust protection, reduce electrolysis, etc... But it seems most of these claims may be unsubstantiated.

 

How often does the thermostat need to be replace??

 

Definately get an OEM T-stat. Ive had atleast two "auto-parts store" ones fail on me. The last one in a sense caused my rebuild..

 

whats the difference between s4 & s5 thermostats? are they interchangable?

 

The FSM says they both open at the same temperature (177 - 182F), but they may be slightly different shape. S4s use a 2 bolt thermostat cover, while S5s have a 3 bolt pattern. This might mean a different shape.

 

I lost 2 water pumps from running straight water. This is no joke.

 

The bolt pattern is of less importance than the sealing method...S4's use a gasket and S5's, an o-ring.
I'm not at all certain that they can be interchanged since I think there might be an installed height difference to accommodate the o-ring thickness.

 

Ah, I didn't know they used an o-ring. I figured something had to be different for their to be 2 part numbers.