Ok to just drain radiator and not engine block?

[StevieC]

Whatever the interval from the manufacturer is I go by 1/2 that and just drain the radiator and refill, that way by the time it gets to the mileage where the coolant would be totally spent system wide, all the coolant in the system has been changed because the radiator holds approximately 1/2 the systems coolant more or less and you are draining and refilling it twice as often.

This way you always have really fresh coolant in the system and lots of active additives for maximum efficacy. My Santa Fe which had a timing belt drove on its original water pump and radiator when the camshaft let go at 535,000km (300K miles) The water pump is supposed to be changed with the belt but I never did it.

 

[Malo83]

My driveway is sloped down, backing my cars in it's easy to drain the block by pulling the lower radiator hose and letting the block drain, easy to flush the radiator while i'm at it, refill with anti-freeze then turn the car around and finish topping off, works every time.

 

[Gasbuggy]

I mean, when you drain the radiator you should also lose about half the coolant in the engine so you're getting the majority of it. Unless the 4Runner has some weird design.

 

[RyanY]

Originally Posted by hallstevenson
On some cars, doing a coolant replacement sometimes gets (excessive) air into the system and some can be tricky to get fully vented. Does this happen when draining/refilling like described in this thread ?

I never had a problem as long as I burp the hose after filling. Any additional air is released to the reservoir, which would lower the coolant level; just top it off if necessary.

 

[demarpaint]

In 40+ years of car ownership and maintenance I never drained a block. I've done flushes and refills but never drained a block. I don't want to jinx myself I only had to replace one radiator, and that was in a vehicle which I owned for 20+ years. My 88 E-150 is still has the original radiator and it is spotless inside. I don't let the coolant go bad.

 

[dlundblad]

It depends on the condition of the system IMO.

A lot of rust junk came out of my truck when I removed the block plugs, but it was neglected.

 

[HowAboutThis]

When I had a Civic that's all I did. Usually got out nearly the capacity it said it held. Other engine designs are probably better at retaining coolant but if you just drained and filled, say, twice as often as required you'd probably be fine.