Coolant overheat Question

[Peter]

I have used the search and still baffled…for an 1986 turbo diesel ...could a low compression engine cause the engine to run overly hot….a slight amount of coolant is going thru the cap when driving…30K/kilo ago installed new rad , thermostat, water pump and 3 thermostats…just finished a 5hr trip and had to fill the plastic tank once…the needle remains study and when the sun comes out will move slight upward and if the hill has an extended climb will turn on the fan

[fatmobile]

 Check to see if there is coolant flowing through the small hose into the coolant resevoir.
 If that is plugged, and it's a pretty common problem, it will cause an overheat as air gets trapped in the head.

[bajacalal]

Are you sure the cap is good? The problem may be as simple as a leaky old $10 cap. I've also seen little cracks form in old coolant bottles.

[Peter]

the small coolant hose going into the plastic bottle is flowing well…found 2 other caps and having no change to the problem…pressure test does not find anything..I am just wondering if the exhaust valves are so carboned up or clogged  so that the exhaust gases are not being removed efficiently enough…the head has never been off with about 300K/mi on the engine...

[wolf_walker]

Headgasket. It's being nice enough to warn you now.

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[theman53]

The water pump you replaced didn't have the plastic impeller did it?

[Dakotakid]

Stop being so logical.