Land Rover Repair: 96 Disco Overheating in Alaska - air in radiator hose, land rover model, head gasket leak

Question
John,

Make: Land Rover
Model: Discovery I
Year: 1996
Engine: 4.0L V8
Fuel: Petrol
Problem: See below

I have a 1996 Disco that is overheating with air in the radiator hose. I have replaced the water pump and thermostat. I keep getting air in my top hose over my thermostat that causes the engine to overheat. Can you please help me identify what could be introducing air into my cooling system. The following is information on what I have done and discovered:

 If the engine temperature appears to be rising I will pull over and bleed the air off of the top hose (loosen the top radiator hose clamp just enough to let the air escape) and squeeze the hose like a pump to get coolant to the thermostat. There are times I may have to do this every 5 minutes of driving, there are other times I can drive for 20 minuntes (most of my trips are no more than 20 minutes) with no rise in temperature.

 I tried to narrow it down, first thinking it was a head gasket leak. I purchased a block tester kit (blue fluid you pour into large glass vapor trap and use a asperator to suck the air off of the radiator) from NAPA (Leak Detector Kit/Engine Block  Item#BK 7001006).  All of the local mechanics I spoke with confirmed that this is a method they reguraly use when a DGA is not available. The engine tested negative (I used the entire kit which accounts for about 10-15 tests and hours of my time) for emission gases in the cooling system. I should also point out that no evidence of antifreeze was found in my oil nor does the vehicle smoke.

 I then spent hours trying to bleed the air from my system, which proved to be a challenge to say the least. After that I did not have overheating for 3 weeks worth of driving and then I began getting air back in the lines.

 I have parked the vehicle since that time and curse it every morning I bike to work (the biking is great fun now that it is summer, but winter is not far ahead and I need to either part it out, buy an inexpensive vehicle with the proceeds and  pay to have its stripped carcass dragged to a scrap yard or fix it and be happy once again.

 Please if there is any help you can offer I would be most appreciative.  

Answer
Hi Charles,

have you examined your radiator?  Micro leaks can exist without leaving a spill on your garage floor or driveway.

Pressure test the rad.

Glad to read that its not a headgasket problem...usually it is.  I always test the rad first then move to the engine.

Enjoy your summer on the bike but get that rad tested soon.

Regards,

JohnMc
Quebec, Canada  
I know all about cold winters too!