My son has a 1999 Discovery II that was overheating on occassion, approximately 3 times a month. I replaced the thermostat and vehicle is still doing the same thing.There is no pattern to the over heat issue. It occurs in all forms of driving from in town to on the highway. The overflow canister ends up with water boiling out of it. The water definitely stops flowing in the engine as the heat in the car goes cold when the overheating occurs.The fans are operating normally. I have not had the radiator removed and checked since the problem is so sporadic I just do not think it can be the raidator.What am I missing here? Have I overlooked something obvious or is there something different about Land Rovers that I do not understand?

 

First thing, if you are luckey and haven't burned the engine, your son has to quit driving it.
When you have worked on it, have you always bled the air out of the system?
I would suggest you do a coolant pressure test to see if you have a blown head gasket leaking exhaust into the coolant system.

 

Mike, I have completed a pressure test of the system on my son's car, I forgot to mention that in my original post. The system appears tight as a drum. I do not think the engine has been blown at this time, but I do not get it fixed soon, it may be ruined.

 

Would a pressure test show a clogged coolant line or clogged radiator?

 

Wolfpack,

Thanks for the input. If a hose or radiator were clogged would I not see the problem all the time? I am at best a "weekend" mechanic and not anexpert in this field, thus I am here with those that are more knowledable than I. I appreciate any other suggestions or info.

Mike,

In answer to you question concerning bleeding the cooling system of air, we have had this Disco II for 2 years and the only time the system was open was when I replaced the thermostat to try to eleviate the trouble. The car did not overheat the first 2 years we owned it.

 

Hah..good point...I guess it's been a long day [&:]

 

Are your electric fans working, how about your main fan?

 

Mike,

The fans are operating normally. I have checked both the electric and the regular fan. If the fans were inop, the car may get hot setting still, but should not overheat going down the road as airflow would be going through the radiator wouldn't it? ThisDevil Disco will decide toget hotgoing down the freeway asquick as it will get hot setting idle on the driveway. I even pulled a fully loaded U-Haul trailer for 4 hours with this Disco and it did not over heat. Note I siad "Dad" drove the car, cautiously watching gauges. This trouble just does not make sense to me what so ever.

I noted another discussion in these forums where someone had a smiliar trouble. The problem with that Discovery I was someone had placed a lot of "stop leak" in the radiator and that crude wasblocking the radiator outlet from time to time. Are the Disco I and Disco II radiators designed the same?

My son is about to head to Washington DC to work for a few months and I do not want him out on the raod until this is repaired. HELP !!!!

Tony

 

i have seen serveral times that the radiators on a disco II and p38 rr have been cloged with a sticky white milk like substance
and i beleave this is from small amounts of combustions gases entering the cooling system over a long
time. (the disco I radiator is a brass radiator and very differant front the disco II)
you may have reduced flow radiator. i think the next step is to but a combustion leak test kit
bluepoint by snap on i feel is the best kit. in this kit is a turkey baster like thing that sits in the fill
cap area and using a special blue fluid air from inside the cooling system will go through the fliud and
if there is combustion gases in the cooling system the fluid will turn green and then yellow.
instuctions will come with the kit.

 

A clogged radiator won't manifest as over heating all the time, depending on how clogged it is. There are too many factors that come in to play when driving.
There are two ways it could be clogged, one is just the fins are blocked with bugs/leaves/dirt from normal driving or off-roading. The other is internal passages are clogged.
I'd pull the radiator and get it flushed. If it's never been done on a 99 it probably wouldn't hurt even if that's not the problem, but I bet it is.