Logo

D4 overheating (or not?)

gkaramalis

New member
I have had my 37' express cruiser with 2xD4-300 engines since 2008. After the first year I noticed the port engine coolant temperature indicator to rise from the normal 85 degrees centigrade to a bit over 90 every time I pushed it above 3000 rpm (I normally cruise her at 2800 - 2900 rpm), then falling back to 85 degrees when I eased her back to 2900 rpm. Both the rise and fall of temperature happens instantly, which does not indicate a true change (which would be more gradual), but feels more like a thermostat or indicator malfunction. This year it has started happening quite some times even at 2800 rpm, staying there for maybe 5-10 minutes and then falling to 85 degrees without any action (again instantly), while other times it rises and falls instantly ("playing" between 85 and 92 degrees). Any suggestions?
 
get infrared laser thermometer, and measure exact temperature to verify what is going on. its a great inexpensive tool, and you can get readings by just pointing it into various parts of the engine. I would check thermostat housing temperature, exhaust manifold temperature, and temperature along raw water cooling circuit. I have seen before where temp gauge reads higher when instrument panel light is turned on, and then back to normal when light is turned off. So check for any electrical components that might be turning on at the same time your gauge jumps up, and turning off when gauge returns to normal.
 
Thanks!!
Following a friend's suggestion, I checked the digital (EVC) reading and it coincided with the analog temperature gauge that I had been reading all the time, showing 92 - 93 degrees centigrade. So, I don't think it has to do with the panel light. I can't think of any other electronic device turned on and off. It looks to me like thermostat matter. Is there any sensor involved, that might be giving wrong data to the thermostat?
I will try the infrared thermometer too and get back to you.
Thanks again.
 
diesel engine doesnt make heat until RPMs are over 3000. i used to have almost completely clogged aftercooler element (on the raw water side), and could cruise all day under 3000rpm with normal temperature, however attempting to go over 3000rpm would overheat in 30 seconds. if evc is recording high (92-93), you most likely have an issue, and 99% of the time its raw water related. Check coolant level first, then impeller blades/integrity, then check for flow at exhaust elbow with engine idling, then check along raw water route with IR gun making note where component (raw water pump, oil cooler, aftercooler, heat exchanger) water exit temperature is much higher than entry temperature. this will pinpoint the obstruction in the seawater cooling path, remove, clean, and reinstall. you have to run 85c or so all the time, no matter the RPM
 
My mechanic suggested opening and cleaning the heat exchanger, since impeller had been changed last March and 60 hours (on the engine) ago. I told him to bring the IR gun along, to check temp differences before anything else. I will get back to you with results. Thanks!!
 
A build up of lime scale the heat exchanger and aftercooler is most probably the issue here, I find that running the engine on a 50:50 mix of Rydlyme sorts the issue most times with out major stripping of exchangers.
 
Check the raw water system and clean the coolers. Unless you are doing lots of hours it seems pretty early to have to do the coolers, but some of the Volvo's don't have the spare cooling capacity that other engines do. They get to sell more engines that way :-(
At 3.7l and 300hp I wouldn't be surprised if the cooling was marginal unless Volvo seriously upspec'd it when they decided to stretch 300hp out of a 210hp engine.
 
Back
Top