savala88

Here's the symptoms they started a about a week ago I noticed that I was having to refill the coolant more often then usual I figured there might be a small leak somewhere. It began to heat up and then quickly fall back down to normal temps. I checked the hoses and notices coolant squirting from the hoses going into the EGR valve. Tightened those but it didnt seem to help, although the coolant isnt disappearing as it was the car will still get very hot(almost to the red line) and then rapidly fall back to normal. what could be the problem?

its a 1990 ls400

NjRican

iTrader: (1)

sounds like your thermostat might be getting stuck then opening when it gets realy hot

deanshark

OR, it could be that there is air in the system, which there probably is b/c you say you need to keep adding coolant. Does the engine actually get hot or is it just the gauge goes to hot? If just the gauge then it's air. Very unlikely would be a head gasket, they don't usually go bad on these engines. I would suggest fixing whatever leaks ya have, add coolant, and bleed the system. You should be set after that. If that doesn't work then I would think about changing the t-stat. When was the t-stat changed last?

Extrudedco

It sounds like air in the system. Top off the coolant at the fill plug after you fix the leak. What's happening is you have an air bubble that collects behind the thermostat, which insulates it from the hot coolant. Once the engine gets hot enough, the thermostat still opens, and the engine cools down to normal operating temperature.

I lived with this problem for a couple years with my last car due to a leaking head gasket. Don't just ignore it, or else you could end up like me...fixing a ruptured heater line in August with a wine key in a gas station parking lot, and missing a friend's wedding in the process.