Hey guys,

What do you guys do to relieve the pressure that builds up in the cooling system when you boost your cars? I was thinking about running a line out of the reservoir bottle. Any thoughts?

Thanks

 

Well, there are many techniques but the one that really works is to replace your head gasket before the entire engine blows up. The coolant system should NEVER gain pressure from boost.

 

Interesting, why do you think its the head gasket? I thought that perhaps pressure was building up because of something to do with the coolant that flows into the turbocharger. Were exactly does that coolant flow?

Thanks

 

The coolant flowing through the turbo is separate from the workings of the turbo. It is part of the cooling system to be sure, but is separate from the workings of the turbo...which is first and foremost oil cooled. The water jacket is added simply to increase longevity as most folks are lax about proper shut down of hot turbos.
Coolant flows throughout the engine in water galleys. These are cast into the engine block and cylinder head. There are matching holes on the top of the block and bottom of the cylinder head for the coolant to flow uninterrupted. The head gasket keeps the combustion gases from entering the coolant system and coolant from entering the oil galleys, etc. Head gaskets fail. Engines with cylinder heads and blocks made from different metals fail sooner. B230's have aluminum heads and cast iron blocks. Different metals expand and contract at different rates. Add to the mix a turbocharger adding positive pressure to the combustion chamber and...the head gasket fails.
Here's three things to check: 1.Pull the dip stick and look at the oil on the end. If it looks like a chocolate milk shake...don't drive it, you have coolant mixing with the oil 2. With the engine cold, pop the hood and remove the overflow bottle lid. Allow the engine to warm to operating temperatures. With the transmission in park or neutral, rev the snot out of the engine a few times, to 4k at least. Not being under load, the turbo will not boost. Coolant erupting out of the coolant bottle is a sure sign of a blown head gasket. 3. If your car passes both of these tests, take it to a shop and have them do a coolant test. They can expose a chemical to your coolant and detect the presence of hydrocarbons which are a by-product of combustion. Hydrocarbons should not be in the coolant.
Trust me...your head gasket is blown...probably between cylinder 3 and 4.

 

Thanks very much for the information. Ok well the good news is that my oil isnt milk shakey, I'll do the cap-less test tomorrow. also I forgot to mention that I see a small coolant leak at the top of were the water pump meets the block, could that have anything to do with it? If I reduce boost back to were it was originaly do you think that will extend the head gaskets life?

Thanks

 

Not really...now that it's breached, it's just a matter of time before your radiator explodes and/or you overheat the engine...

 

sort of off your guys subject here but is there any difference to the head on my non-turbo 90 740 GL and a turbo version

 

The head casting is the same...it's a 530 head. The difference is that turbo's have stellite coated, sodium infused exhaust valves to better dissipate the additional heat. Lots of folks have run n/a valves without issue...

 

well the main thing is I am thinking about trying to turbo my engine and am trying to figure out if it will hold up and what modifications I am going to need to do it

 

Any Volvo redblock that is 20 years old has a headgasket that's not too far off failing, all it needs is the right conditions.
I've pulled a few heads of unopened redblocks and the gaskets have all been ready to fail in many locations. It's not a design flaw, just the fact these engines last so long the gaskets plain die of old age and heat cycles.
At the very first sign of a suspected head gasket issue, change it out.
I've also had head gaskets weep externally when using the green cap for prolonged periods too.
Don't ignore the symptoms and assume you must have all the signs for a head gasket failure, there are many indicators for head gasket failure and even one of them means you must dig deeper or risk losing the engine.
I've run a 740 turbo with 14psi of boost in some extremely hot weather and NEVER had a problem with excess coolant pressure. Those that do have poorly maintained vehicles.

 

so what your saying is if I am going to run a turbo I am going to need to do some preventive maintenance before I strap on some boost?