Airlock?

Speedfreak

Speedfreak

Active Member
Ive just replaced my water pump and rad. I'm now experiencing a small rise and fall in temperature in normal driving conditions, almost in to the red at the top end of the fluctuation. Also the rad is sometimes cool and sometime warm/hot at the top.
I think I may have an airlock? Anyone have any clues how to cure this? Many thanks.
 
How did you refill the cooling system? Are both heater hoses hot at normal running temperature? The rad should be hot at the top when the stat opens, and be cooler towards the bottom and towards the bottom hose outlet, that shows the rad is doing its job.
 
Hi, Yes both heater hoses hot. Top of rad is sometimes warm/hot and sometimes very cool. That's all at normal running temp after a good 20 mins driving. Btw I filled system from the top of the rad, slowly from a bottle.
 
I refilled (with the heater set to hot) by the top of the rad, slowly from a bottle. Perhaps not slowly enough?
 
The position of the heater controls makes absolutely no difference whatsoever, it's a flap heater so coolant flows through the matrix all the time. Fill with coolant, then run the engine until the stat opens with the rad cap off, then once the stat is open, rev the engine to 12-1500 rpm, watch the coolent level in the rad drop, and top up to within 2" of the top of the rad, with the engine at that RPM, and then with it still at that rpm, fit the cap.
 
Harvey's procedure is spot on for filling the radiator. If you still have a problem after doing that, then I would suggest checking the thermostat. I always check thermostats even if new prior to installation. Is it the correct temperature thermostat? Is it the correct type of thermostat, in stalled the right way around?

Here is what they look like:

http://www.rockauto.com/catalog/x,carcode,1312573,parttype,2200

I would suggest 180 degrees should work fine. In a warm climate you may need to try a 160 degree thermostat, however TC's tend to foul plugs if they are run too cool. I run 180 in northern NY in my TC, and 160 degrees in my SC automatic, which is in Australia, a warm climate! Original spec on the 2000's was 170 degrees, which are hard to find. The 2200 spec was 180 degrees.

James.
 
j_radcliffe said:
Harvey's procedure is spot on for filling the radiator. If you still have a problem after doing that, then I would suggest checking the thermostat. I always check thermostats even if new prior to installation. Is it the correct temperature thermostat? Is it the correct type of thermostat, in stalled the right way around?

Here is what they look like:

http://www.rockauto.com/catalog/x,carcode,1312573,parttype,2200

I would suggest 180 degrees should work fine. In a warm climate you may need to try a 160 degree thermostat, however TC's tend to foul plugs if they are run too cool. I run 180 in northern NY in my TC, and 160 degrees in my SC automatic, which is in Australia, a warm climate! Original spec on the 2000's was 170 degrees, which are hard to find. The 2200 spec was 180 degrees.

James.
Click to expand...

I filled her up as instructed, OK all day, did some Motorway and town driving and all seemed good, however when I got home a huge amount of coolent was expelled via the over flow pipe by the rad cap. All of a sudden after switching off the engine. If thermostat was faulty would you expect this sort of behaviour? I'm starting to think the head gasket may be in need of replacing....anyone else had this behaviour?
 
It shouldn't do that. Test the cap to see if it can hold pressure, if you can't test it then eliminate it as the cause by fitting a new one.
 
if you suspect an air lock running with the engine cool and slightly undoing the top heater hose and making sure water comes out and doing it up once you've seen it flow out can help....
 
Sounds a bit like an overheating problem or a localised hot spot. What is happening is that when you stop the engine the water pump stops circulating the coolant through the radiator and the residual heat retained in the block boils the coolant, but you must have been pretty close to boiling anyway for this to happen and the problem will be made worse by a faulty cap.
 
I had the same problem with my Land Rover, water being ejected when switching off the engine and it was the cap. Replaced it and all OK. This as happened on a number of vehicles over the years and apart from one instance of a blocked radiator, it has been the cap at fault.
 
New cap fitted(blimey that's a tight fit) I can see in the top of the cap there is a rubber seal. That seal is missing on my old cap so I guess that won,t have helped. New thermostat goes on this weekend. Fingers crossed.
 
"I can see in the top of the cap there is a rubber seal. That seal is missing on my old cap so I guess that won,t have helped."

You have bought a recovery radiator cap, to replace a non recovery type. This is okay, a recovery cap can be used in a non recovery application, but not the other way round. I assume that you do not have an overflow / recovery bottle? You can add one very easily if you drive in a hot climate. With a recovery bottle you know that you will be using 100 percent of the radiator capacity.
 
j_radcliffe said:
"I can see in the top of the cap there is a rubber seal. That seal is missing on my old cap so I guess that won,t have helped."

You have bought a recovery radiator cap, to replace a non recovery type. This is okay, a recovery cap can be used in a non recovery application, but not the other way round. I assume that you do not have an overflow / recovery bottle? You can add one very easily if you drive in a hot climate. With a recovery bottle you know that you will be using 100 percent of the radiator capacity.
Click to expand...
Ahh thanks for the heads up. You are correct I do not have a recovery bottle, however I think you are saying that I am OK to use the cap with the rubber seal anyhow?? Moving forward I may fit a recovery bottle.
 
Thanks to everyone for you help with this, and you were correct. New rad cap has stopped the old girl spurting coolent all over the garage floor when I stop. More importantly the teamp gauge is now sitting right in the middle of the green. Rises a tad when I turn engine off, however recovers in a few moments when I fire up the engine. Falls a tad at speed on the motorway, however these rise and falls are very small. At all times I'm well in the green and nowhere near the red zone! So guys a new thermostat has made my day, also no broken studs!
 
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