This will prob. be long,But will try and make it short?
1999 land rover/range rover,4.0 V8,Manf. date 11/98.its a very good friends ride,138,000 miles on it,Some a$$hole charged him 2400.00 to replace radiator,thermostat,and hoses,but not water pump,then after i told him,radiator needen replacement,any mechanic should power flush system and replace water pump,he went and had water pump installed,also heater core had been bypassed.
SYMPTOMS:drive it for a day or so,then right back to overheaten,this is the problem after the radiator and thermostat and gasket job,and still after a new water pump.
so i checked it out and it did have a bad head gasket.
Now what i want to know is:After i get it back together,can i be assured it will stay cool with the heater core bypassed?In my opion,on a pressure run system like this,without that extra 1/2 gallon of water running in and out of the heater core,and motor,It can affect the cooling process,Unlike chevy and other makes-that only run water in and out of the motor through the H/core,when the heat/cool dial is turned on,these motors run coolent in and out reguardless of A/C being on or heat being on.
Any suggestions let me know?thanx and god bless our troops and america.

 

How do you know it is overheating? Are you going by the gauge or is coolant spewing out. If you are relying on the gauge, it was probably never overheating in the first place. Check it with a different type of gauge. The heater core is most likely bypassed because someone didn't want to change the o-rings. Hope that helps you.

 

Seen this a hundred times, slipped liner, did you check the liners when you had the heads off ?

 

OK,When the temp guage went to red,the coolent was flowen out of the jug.But thats past tense,2nd:after pressure testing and ellemating the problems and finding the leaking head gasket problem,i removed the heads and first thing i did was check the sleeves,and all are well,none have slid down any.So once again my question is?:AFTER i reinstall the heads and new gaskets etc;... is there any reason to beleive or worry about,that it might still overheat after a few days,becuase the heatercore has been bypassed???? Im still waiting on the headgasket kit to arrive from british atlantic,whitch should come in tommorrow,then ill be putting it back together.

 

I doubt that the flow through the heater core has much if any impact on the overall cooling of the system but why was it by-passed to begin with ? O-Rings ? Easy enough (if fiddly) to replace while you are waiting for your other parts to arrive.
On another note, I hope you have had those heads skimmed and crack tested, this a notorious weak spot on these older V8's and you won't be the first person re-install a damaged / cracked head only to face another tear down.Another big cause of overheating is the viscous fan clutch.
BTW, NEVER drive one of these beasties if the temperature gauge goes past the 12.00 position. Let the sucker cool off before your engine becomes an expensive boat anchor.

 

You may or may not be ok with bypassing the heater core, these are sensitive vehicles. I also have to ask why did you bypass it to begin with? Also, how bad was the head gasket? You would be surprised how long a rover will run with a blown gasket and show no signs of it except for a very clean cylinder and spark plug. The temp gauge is very unreliable and will move all over the place due to electrical shorts in the system. Once you have it buttoned up, see if turning on your heated seats, wind screens, and mirrors will cause the temp to rise. I also found that if it says it is overheating, pull over and turn it off. Then turn the key to the on position, most of the time it will return to center indicating a short.

 

This solved my overheating issue.....
I have a 1996 p38, the water pump went bad, so I replace it along with the therostat, upper and lower Radiator hose. Filled it with 50/50 coolant (per the manual), drove it for about 20 min.'s then watched it overheat. I couldn't figure out why it was overheating the radiator wasn't clogged. A friend of mine explained it to me and provided the fix... when I filled the coolant reservoir it didn't fill the engine block all the way, there was still air in the system, so the coolant would get hot and boil back through the reservoir before it got hot enough to open the the theromstat and allow the coolant to flow. The Fix: When everything is cooled off, disconnect the upper radiator hose (from the radiator). Pour coolant through that hose directly into the engine block until it is full, reconnect the hose, top off the coolant, then start it up. This makes sure there is no air in the system, thus as the engine block heats up all it is heating is coolant (not air), once it is hot enough the theromstat will open and the coolant will flow. Hope this helps , it worked for me.