My trooper is overheating only when im doing 70mph for about 7 miles it never does it at lower speed ive flushed system changed stat changed rad cap it does,nt lose water head gasket fine

Usually means the head gasket is leaking pressure into the cooling system, or the radiator cap is faulty.

When its cold remove the rad cap, start it up, put your heater blower on full and full heat on, then when the engine gets hot look inside the rad you should see the water flowing. If its not flowing feel the top of the thermostat housing/rad hose it should be nice and hot, it its not your stat is not opening. Are you sure you got the correct temp stat for this car? Was it properly installed and is the system full with no air in it? You can also get a melt stick from your local Napa, making sure its the right temp stick for your car, put it on the stat housing and see if it melts. If it does and you still have no flow either its stuck closed, or its the wrong temp stat.

Remove the thermostat temporarily just for a diagnostic strategy. Put the thermostat housing back on with a new gasket and then drive it for a time to confirm that it is no longer doing that same thing. You will be running too cool to leave the thermostat out and you will have little or no heat. I just want to know if removing the stat helps before I continue. let me know.

vast ways to overheat. do you want a list?
got signs.? just the gauge or got steam... do TELL?
if it really overheated, did the fans come on.
did you read all the diagnostic steps on the FSM? (alldata.com)
or at suzuki pit stop plus for 4 bucks?
have you, tried to replace anything yet>?
do you want to guess or TEST.
one way is long and expensive , other is save money
your call,
most DYI , do the never done full cooling service, now.
full flush and new thermostat.
6 year old thermostat are kind , END of LIFE now.

signs:
(rad id full of 50% antifreeze, look in rad not the overflow tank) COLD.
1: belt slips? to pump? makes noise or just slips?
2: fans never come on.
3: engine pings. (knocks or detonates)
4: steam or water spouting from RAD or side tank?
5: water in engine oil? or a/t trans? (dip stick end looks milky)
6: carbon dust in the AF , when looking on dead cold , rad cap off neck hole..
7: guage lies, or surges. gauges do lie, or air in the block below STAT makes this happen, no sender or STAT can work in AIR POCKET.
none. so did you really check the level cold at RAD cap off?
8: lost engine power?
9: try a new RAD cap yet, for 5bucks. (if the GASKET IS OK, IT'S OK)
10: if all the above works, Use any IR pyro heat gun meter, to see
if all rad tubes, (hot) read the same, top and bottom
if side flow rad? left and right,. each tube starts at about 180F
and drops by up to 50F degrees. to 130F at the other end of tube
if one tube is same temp end to end,it's clogged,

if all that pans out. the pump is bad.
like this one.

http://www.fixkick.com/Cooling-engine/electrolysis1.jpg



the gun
http://www.fixkick.com/my-IR-GUN.gif

for about 15bucks at Harbor Fright (pun)

im sure i missed a test. but that happens as you proceed.
as you gather evidence you will, do other test. or actions.
diagnostic logic.

no, not special but you failed to stated engine, there are many engines.
and some are very tricky here, like 2.0L.
First state the symptoms,
your post states its overheating, then no heat. (why?)
old post. but others might
Ill post , overheating ,
Example if me, with overheat.
I see my dash gauge, show overheating and engine power drops and pings, then steam vents from the rad, cap?
Over heating (ill skip cab heater but on 2L this path blocked causes thermostat to go quite nuts. not posting engine, makes this hard.)
1: full of 50% AF (antifreeze)
2: new thermoSTAT they age and fail fast. so get a new one.
put STAT in with the wax slug down, and jiggle bleed pin forward.
get air out of system after filling, (RTM)
start car, and....
4: then using and IR pyro gun we then check that
the thermostat housing hits 170F min. but not too hot.
run motor till top rad hose gets too hot to touch 180f is normal.
I had to drive 10 miles, to get it up to 180F.
my car has the hotter, 195 STA,T so runs at 195f. (helps cooling)
USING the pyro gun , the top and bottom of each rad tube.
This tool is Amazing.... and saves burn hands.
if the bottom of any RAD tube is way less than the others?, that is
a clogged UP rad tube. solution is , NEW RAD.
Usually rad repairs, are more costly than new. IN USA.
The water pump must spin at full speed, belt tight.
The impeller or some suz, motors likes disappear. from electrolysis action. so not looking at the impeller is a FAILURE on the mechanic side.
if this car has 2.0 I-4 (4 banger) it has a coolant tube on the rear
of the STAT housing, this tube must flow coolant at all times.
if it dont, the thermostat , will go nuts.
nuts means, that insufficient flow passes the thermostat wax block
causing the thermostat to cycle in a wild and random way.
I dont like this design but is reality. If applicable.
post country, post engine type and state the symptoms.

will it sounds like u tryed everything except what could be cousing the problem it is probley the heater core is pluged with hard water or calcium build up or is just pluged and a rad flush wont flush the heater core unless you start the vechial and flushing the rad to do the heaterd core to turn on the heat to high and the fasters fan speed and make shore the van is running.

is your water pump circulating the water nissans used to have a problem with impellers on pump
leave rad cap off and run enginge should see water circulating when stat opens

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.

Start with the cheapest part and that would be the thermostat. They are easy to replace and that appears to be the issue. They do wear out or stick.

Your radiator efficiency has been reduced by (what is called) blossoming. Blossoming is electrolytic growth of crystals inside radiator duct passages. This typically occurs in the older Troops as gradual overheating probs cause the vehicle to run low on coolant, then water is being used to top off system repeatedly, acid levels in cooling system rise as the coolant protectants degrade and the inside of the radiator ducts 'blossom' with small crystalline growths that reduce the radiators flow and ability to cool the engine. Flushing and blowing out the radiator are temporary fixes. Replacing the radiator is the permanent fix. You did the right thing by replacing the water pump, tstat and radiator cap. An old, original water pump usually fails soon after the radiator is replaced. New Trooper radiators are fairly cheap, $85+. The replacement can be done by any backyard mechanic or DIYer in under and hour. You know the typical warnings about the toxicity of antifreeze and the deadly affects on pets who drink improperly disposed coolant. Good luck to you. It's an easy remove and replace. Your Trooper will thank you with many cool running miles. -Geoff