Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Can a coolant pressure check damage a 10 year old van?

Hi, I have a 2000 grand caravan that lately there is a little white in the oil cap, the coolant is 1 inch below minimum and the heater is hardly working - so, sadly, I’m thinking either head gasket or intake manifold. The vehicle is pretty good otherwise except kind of rusty and the oil pan is really rusty. I want to get a coolant pressure check done so I know exactly what’s wrong with it, cause I know you shouldn’t drive a vehicle with intake problems due to leaking of coolant into your oil, etc. But, I am worried if I get a coolant pressure check done that the test itself may spring new leaks in the system or damage the system more? Anyone know if it works like that? I’ve seen there is another thing like a turkey baster that you can get some coolant out and if it has oil in it changes a different colour - do most garages have this - and is it as good as a coolant pressure check?

If it is bad, I want to try some silica sealer when the weather gets warmer,since it is a pretty old car and I don’t want to put alot more money into it. I already put in some tie-rods, a tranny pan, timing belt with special non-slip rig, rear shocks, tires, front strut work. I am disabled and living on a very small fixed income.

One garage I went to said its probably just condensation - but they didn’t even look at it , and I am suspicious, and I want to catch it before the engine is toast if possible. It is the 3.0 l. v6. I bought it a year ago, and the owners didn’t do much maintenance on it - the plugs and wires are original and I don’t think they’d changed the air filter in years (if ever). The oil was newly changed before I bought it. I have put 40,000 kms. on it since I got it, mostly highway.

When you pressure check the system, you should pump it up only to the rated pressure of the cap, so it is unlikely to provoke further leakage, and if it does, it is just triggering something that was just about to let go anyway. Might as well find out about it now.

If recent trips have been short trips, then a little white under the oil fill cap is nothing to worry about. Pull the dipstick when the car has been running. If the oil on the dipstick is milky, then you may have a problem.

Sampling the water for the presence of oil, is interesting, but remember that water in your oil (if indeed you have water in your oil) does not necessarily mean that there will also be oil in your water. Depends on where the leak (if any) is located.

I understand the temptation to use radiator sealant in an older vehicle, but do not use it unless you need it. If the choice is to junk the car or try sealant, then try sealant. That stuff can keep you on the road, but it can do a lot of damage too.

A properly operating cooling system always operates under pressure. The pressure is controlled by the radiator cap. When the pressure reaches a certain psi level, the cap allows the coolant to flow into the overflow reservoir. The pressure test just simulates what should be happening when the system is functioning correctly.

When I had a leaking water pump and needed to make it home, I loosened the pressure cap on my old Rambler years ago. This reduced the pressure and I made it home. I changed the water pump right away and, of course, tightened the radiator cap. If your cooling system isn’t maintaining pressure, the coolant loss may be slowed. I don’t think a pressure test will make the situation worse.

Yes, especially if the radiator is weakened and leaks a little, already. Been there, done it. By taking the pressure tester up to 15 psi, which is the normal maximum working pressure of the cooling system, the cooling system pressure may go higher than the vehicle usually goes (which may be, say, 11 psi). Remember, at max operating pressure, the radiator cap releases at 15 psi.
If YOU are doing the pressure testing, don’t pump up the tester more than 10 psi. If 10 psi causes it to leak a lot, you were just days away from the same thing, regardless.

Thanks for all the replies guys, it’s a big help! I try to be a “car gal” but there is alot i still don’t know. I just came back from checking the cap again (last time a day ago) and it is just oil now, so i hope its ok, but lately I have been parking it nose uphill rather than nose downhill - would this make a difference depending where the gasket was leaking? I’m suspicious, cause when I bought it, they had the rear end kind of sagging. If its the water pump, I will be happy cause its not soooo bad. I’ve topped up the coolant and I’m going to keep a close eye on it.

Before you do the coolant prssure check take it to a shop that can evaluate the cause of thet “white in the oil cap”. A coolant system pressure check only checks for leaks, your white gump and your poor heater operation are from some other cause. You may meed to flush the system and a pressure check done first would have meaning less.

And yes, you may have another problem causing contamination of the fluid and perhaps also of the oil. You’ll want to look into this.