'90 740 - heater core hose routing

e777 · Post by **e777** » 06 Oct 2010, 22:46

I was wondering what the proper routing was for the two hoses exiting the heater core into the engine compartment. I'm not 100% sure the routing is correct right now. Thanks!

90 740 N/T
270K

Retired MVS Contributor · Post by **Retired MVS Contributor** » 07 Oct 2010, 07:04

A hard line (pipe) comes off the water pump on the right side of the engine and runs to the firewall behind the engine...It changes to a hose behind the engine and connects to the LOWER firewall feedthrough...

e777 · Post by **e777** » 07 Oct 2010, 09:06

Thanks for the info. I'm glad I asked, given that the pipe/hose leading from the water pump currently feeds into the UPPER fixture on the firewall leading to the heater core.

e777 · Post by **e777** » 08 Oct 2010, 08:50

The hose that should connect to the UPPER heater core tube in the firewall should then connect to the water heater valve on its way to connecting to a point near the motor head. Is that correct? Thanks again.

Samm93 · Post by **Samm93** » 06 Dec 2020, 05:06

So how can I re route the line that goes to the pump in order to gain more heat in the cab I live in Alaska and it gets fairly chilly up here and even though my blower motor as well as my heater core are both functional I still only get so much heat from my heater it's hot just not as hot as I'd like

e777 · Post by **e777** » 06 Dec 2020, 11:05

I'm not sure about rerouting. However, a friend of mine did a thorough coolant flush - including a flush of the heater core - and he says it raised the maximum temperature of his heater output by several degrees. You may want to try that first.

Post by **volvolugnut** » 06 Dec 2020, 11:19

Do you have the proper engine thermostat that is working properly? A bad thermostat is likely cause of poor heating. The 240 and 740 cars have very good heaters.

I agree a good coolant flush is good idea if it has not been done in a few years.

volvolugnut