I replaced an engine in a 89 DL wagon (Jap motor w\40k on it).

 

It has an occasional overheat problem. Doesn't seem to matter what the outside temp is or driving conditions. Can go for several days (owner puts on 60 miles per day driving to work) without heating up and then all of a sudden one day it will overheat. Timing has been rechecked and is right on. Almost seems like a restriction in a hose (flap of rubber etc...).

 

Was advised to replace radiator.... had flow checked on current one and it seems to be ok.

 

Any suggestions!!!

 

Jamin

Thermostat?

What kind of conditions does it overheat under? City driving? Highway? Does it lose coolant at all?

Thermostat?

Have tried two known good stats.

What kind of conditions does it overheat under? City driving? Highway? Does it lose coolant at all?

It usually happens going down the highway. Seems to boil the coolant out of the overflow tank but leaves some in the rad.

>> It usually happens going down the highway. Seems to boil the coolant out of the overflow tank but leaves some in the rad.

 

Exactly the symptoms I chased a year ago -- the radiator cap, or the radiator, or both. The cap gets old an weak and can't hold 14psi, so coolant expands into the "overflow" tank, air gets sucked back into the radiator when it cools a bit, and it's a vicious cycle.

 

But my radiator was 15 years old at the time, and I replaced that, too. The inside channels collect a layer of scum, and over the years that adds insulation so heat transfer suffers. If it's the original radiator, consider replacing it.

 

Overheating at highway speeds points to the radiator. The engine's doing a ton of work, and it has to shed heat. The cooling system isn't overdesigned enough to allow for an inefficient radiator in that case.

 

-- Mark

>> It usually happens going down the highway. Seems to boil the coolant out of the overflow tank but leaves some in the rad.

 

Exactly the symptoms I chased a year ago -- the radiator cap, or the radiator, or both. The cap gets old an weak and can't hold 14psi, so coolant expands into the "overflow" tank, air gets sucked back into the radiator when it cools a bit, and it's a vicious cycle.

 

But my radiator was 15 years old at the time, and I replaced that, too. The inside channels collect a layer of scum, and over the years that adds insulation so heat transfer suffers. If it's the original radiator, consider replacing it.

 

Overheating at highway speeds points to the radiator. The engine's doing a ton of work, and it has to shed heat. The cooling system isn't overdesigned enough to allow for an inefficient radiator in that case.

 

-- Mark

Thanks for the headsup. I figured that was probably what was happening.

It is the original rad but I have one on order for it.

 

appreciate the feedback.

 

Jamin

Yah, the exact thing I'm experiencing right now. I was able to make it over a big mountain range to start the drive with no overheating then about an hour later on the long straight away, it begins to heat up. I'm losing coolant too and I'm not sure where it is. The next time it heats up, I'm going to check the fans and see if they are on.

 

 

Simon