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What coolant is best for a c4 L98?

stiej1977

CCCUK Member
I've been planning a coolant refresh on my 87 L98. i see the prestone stuff available in local Asdas etc. is that the right stuff for my year/engine? the bottle says it's fit for anything....
 

JonnyC4

CCCUK Member
I run ACDelco Dex-Cool Coolant in my '88 L98. Never had any problem with it. This is what they run also in modern Corvettes and it keep your system clean.
 

stiej1977

CCCUK Member
I run ACDelco Dex-Cool Coolant in my '88 L98. Never had any problem with it. This is what they run also in modern Corvettes and it keep your system clean.
Ok thanks Jonny. I’ll look that up. Where do you buy it from? You’re in the Netherlands aren’t you?
 

JonnyC4

CCCUK Member
I work for Opel/Vauxhall, they have it in stock at my work. Normally they have it in every Vauxhall dealership.

I'm in Belgium.
 

dm575

New user
There's lots of discussion about Dex-Cool on the US forums, I believe it was introduced with the LT1 engine and doesn't mix with old tech coolants. Not claiming to have the full info but I would advise doing your research before using it :)
 

JonnyC4

CCCUK Member
There is no problem with it, as it's being used in other GM cars and even Opel/Vauxhall cars. I'm running it now for a whole while, without any trouble.
 

Redlevel

CCCUK Member
As the '87 is an old technology classic car, you need non OAT (2 year silicate glycol) coolant.

There's been too much talk and warranty legal issues with Dexcool to take the chance on it. I play safe and use Bluecol or Bluestar in my own daily '87 and change it every two years. No problems and its normal running temp is 175-185..

If you do this and want to change to a 2 year coolant, flush and run thoroughly a few times (I use and run with a crushed dishwasher tab after the first drainage to clean it out well) as Dexcool will turn to Angel Delight in the pipes and galleries if you don't get rid of it all, so be advised
 

teamzr1

Well-known user
The early issues with using Dex-Cool was the vehicle owners were allowing the water to vaporize which caused the Dex-Cool to get thicker
because they were not assuring the coolant level was filled to proper level
As long as not mixing with other brand types Dex-Cool will be fine and does a better job of keeping rust down and does
a better job at higher coolant temps.
Dex-Cool became a standard and other anti-freeze makers sell a brand that meets the Dex-Cool makeup

I have only used Dex-Cool since my new 1984 C4 and even in hard hot racing worked just fine
 

stiej1977

CCCUK Member
Thanks all for the helpful advice. I'll make my choice after some consideration of the above replies.

is it ok to flush out the coolant system this way: remove radiator cap and bottom hose, drain, replace bottom hose, remove both knock sensors (each side of the block) and flush through by sticking a garden hose into the radiator using the garden tap?
 

teamzr1

Well-known user
While your doing this why not get some coolant flush and clean out the whole coolant system ?
You could get a coolant Tee to cut into a heater hose. Some flush kits come with that tee.
Also if the engine coolant thermostat is old good time to replace it with like a 180F deg one.

Follow the instuctions of flush product and
Then with opening up the radiator cock to coolant/flush drain out after connecting to a water faucet hose to that Tee, with engine at idle and the heater on run that water through and whole system will get flushed.

If installing that coolant tee, it can be left into that heater hose.
Maybe your auto parts store can test your radiator cap to see if still at correct PSI (pressure) relieve or if cheap replace it.

Once replacing water/anti-freeze engine might need 2-3 cold/hot cycles and check as there may have been some air in system
and top off coolant to fill level
 

Redlevel

CCCUK Member
I have a 160 thermostat and a fan controller that keeps it at about 175-185 in all weathers (its a daily all year round). Not got the bottle for this 230deg stuff after my fan failed one time and it hit 260 in an instant! I like some warning of impending doom! Been that way for 10 years now, without any problem.
For flushing, I backflush when I can, and use a crushed dishwasher tab to clean it out before I refill.
My radiator cap is one of those ones with a lever so I can burp out any air safely.

Tips..
When fitting a new thermostat, bore a couple of 3mm holes each side of the flange to allow air to pass to the top of the radiator.
Leave the block plug and knocksensor in place or you might find it and its threaded hole, will crumble.. Let sleeping dogs lie.
 

teamzr1

Well-known user
Another way to purge out air pockets easy is put the thermostat in hot water until it opens
Take Tstat out of pot of hot water, before it closes put like a hard aspirin in-between the opening so that when
Tstat closes the aspirin will prevent it from fully closing

Install back into engine
Fill coolant system, being Tstat is still open the water and air pockets will flow and air will purge out
Start engine, once it is hot the Tstat will fully open and aspirin will fall down and then de-solve doing no harm.
 
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