well i busted a heater control valve hose,and im wanting to do some stuff "while im in there".well,i want to do a full gasket job but i want to check the compression first to make sure im in need of a head gasket change.my questions is could i check my compression without coolant in the system?TIA

 

What hose, on what car? Compression test is best done when engine is up to operating temp. (hot), not when cold.

 

i busted a heater control valve hose on my 87 951.

 

You can check the compression with the engine cold, but it won't give you an accurate reading. On my car with 150psi compression when warm, registers something like 130 cold.

 

thanx ken and danno.so can i do a compression check without coolant in the system?i see it kinda waste if i fix the busted hose,do a compression check only to find out that ill need to drain it again because of a bad headgasket.thanx again

 

Fix the hose and just fill the cooling system with water. Do a proper compression check with the engine "hot". If the compression check is OK, then just flush and fill with coolant.

 

Jut don't forget to have WOT (Wide Open Throttle) and pull the DME (fuel pump) relay.

 

If you are the type who can handle risk, then it is possible to warm the engine without coolant by idling it for a minute or two.

If there is some coolant in the system, then the temperature sensors will work on the steam, that is generated and if there is no coolant, then the only feedback is your hand.

I have successfully run my 750iL without coolant for 4 miles to the mechanic (burst hose) starting with a lukewarm engine.

Laust

 

thanx again guys!

 

I'd just test it cold, that's my opinion. It's not as accurate as a warm test, and the numbers are always lower, but if you have a head gasket issue, you'll find it on a cold compression test.

 

Leakdown test is the only way to ensure it is the head gasket and not another internal problem. Plus you do not need to have coolant in the system.

 

well thanx again to the help of rennlist!i just did a compression check and all 4 cylinders showed 120psi.so everything seems fine with my headgasket and all.thanx again guys!!!!

 

i forgot to add that,when doing the compression check,#1 and 2 couldnt hold the #.like,it would hit 120psi and go back to zero or each time the engine would crank,it would hit 120 and drop,120 and drop and so on.could this mean that i have a blow head gasket?TIA

 

Why do you think you might have a head gasket problem? Many of us have had small leaks that weren't revealed by a compression test. And I'm not clear on why you'd want to do a head gasket job while you're fixing a burst hose. Your numbers say your rings and valves are OK, but if you're seeing head gasket symptoms, those numbers do not rule out a slow leak.

 

the cam tower gets real hot real quick.so hot it chips the paint off of my hood!i dunno whats causing my engine to get so hot.i just changed the thermostat a few months ago,flushed out the system,try bleeding the system(might have some air).i even changed all the vac hoses and took out the CV,HCV,ISV and Venturi.updated all the hoses and still getting 14"hg at idle,thats when its hot because my engine gets hot in 5-10 mins. from startup.TIA