D1-30 overheating after running above 2000rpm for some time

[jlavery]

I know there are several threads on overheating Volvos, but want to distil my experience and garner some advice.

Symptoms:

• Engine been running fine for some time, but recently has had overheat alarm after running at more than 2,000rpm for a long period (1 hr).
• When up to temperature but not alarming, engine seems hotter than should be to the touch, but runs fine.
• Raw water system is fine. Good flow.
• Raw water out through exhaust seems unnaturally cool, would expect it to be hotter.
• When engine up to temperature, can see coolant entering expansion tank via the thin (overflow/relief?) pipe
• Coolant pump turning find, and belt tension seems OK.
• I've taken front off the heat exchanger and it looked OK. Ran a coat-hanger through holes to clear any debris if there was any I could see.

Thoughts:

• Heat exchanger blocked at other end? -> Should I remove completely and check?
• Coolant pump broken? -> How can I check this?
• Thermostat not opening? -> Check this by removing and seeing if it opens in a pan of hot water? Do I need a thermometer to check operation temperature?
• Other?

Thanks!

James

 

[jlavery]

So I removed and tested the thermostat - working.

Removed (with a bit of effort) the exchanger core). Wasn't bad at all, cleaned out salt side and scrubbed fresh side - no chemicals available.

On reassembly, seems to be behaving better, although to date have not run at higher revs for a long time.

Meanwhile it occurs to me that the fact that I'm getting lots of hot water in the calorifier indicates the fresh pump is working - convection unlikely to be circulating the water that efficiently.

 

[penfold]

HX may need pickled if everything else is as you've described.

 

[jlavery]

Yes, pickling the HX is on the list (if that's what you mean).

 However - rear O-ring teltale on HX is leaking now, after several hours running. So will need to replace that O-ring when I've got a new one.

Thiink OK to run still - or will I be gettin salt water crossing into fresh? Need to check schematic.

 

[penfold]

What is coming from the telltale? New O rings are a good idea after servicing the HX, the old may be damaged on removal and depending on age will have lost flexibility. Not sure how it works at the far end, two O rings in the one groove is odd.

 

[jlavery]

Salt water steadily dribbling out of telltale, and eventually filling engine bilge. Exhaust elbow pipe (short flexible one which is a bugger to get back on) might also be leaking slightly.

Annoying that happened now 1/2 way to Muck, and not when I ran the engine for an hour under load on reassembly!

 

[jlavery]

What is coming from the telltale? New O rings are a good idea after servicing the HX, the old may be damaged on removal and depending on age will have lost flexibility. Not sure how it works at the far end, two O rings in the one groove is odd.

View attachment 159605

Thanks for diagram, I have workshop manual.