225 Thermostat Prob?

[Matt Cole]

Chaps, i've had the 5 out today for a blast about. First real go since the engine conversion. Im having trouble with the cooling system still. The problem is the stat opens at 100 deg (89deg stat) then the rad heats up cool water flows round and the engine temp drops to about 80deg. Thing is the temp aint steady, it goes back up to 100 deg then stat opens and back to 80. Its as if the rad is over cooling/too large?? Im using the 172 rad.Any ideas? Is the rad too big??

[Scoff]

temp going up and down sounds like its air locking, are you running a pipe from the top port of the stat housing to the top of the header tank ? you need this to get rid of air that might otherwise pile up in front of the thermostat.

if the header tank is piped as above then you should be getting water running in to the header tank through that small pipe, especially when the stat is closed. is this happening ?

if all that sounds OK then have you tried a new stat incase that one's buggered ?

the rad won't be too big.

[Matt Cole]

Cheers scoff. Originally i did have the pipe from the stat housing to the top of the header tank. On the original 225 set up this port is blocked off. What i have done is reverted back to blocking that port off and im using a pipe from the top of the rad to the header tank to aid bleeding the rad ( i think we discussed this on another thread). The thermostat is new and i have tried others but it does the same. Are you suggesting i should re- enable a pipe from the stat housing to the top of the header tank?? Any idea why this port would be blocked off on the original set up?

[Scoff]

well, yeah maybe. maybe the other heater matrix ports (or turbo jacket ports in your case ? IE the pipes on the side of the stat housing) are enough to bleed off the air and get hot water onto the stat. but I think that the top port that comes off RIGHT before the stat aught to go back to the header tank to be sure there is no air there. maybe you could run both that and the rad-top pipe back to the tank, connected them with a T piece.

also, you could try drilling some small holes in the stat disc, that should make sure that water flows over the stat all the time.

[Matt Cole]

i did think about drilling the stat chief, but im thinking there is some underlying fault with the pipework. I do remember some of the pipes used for the turbo run etc had some small restictors in, but i thought they would not affect the main engine cooling circuit. This is also messing around with my adjustable temp fan switch as i can't get a steady temp after the stat housing.

[Scoff]

thats another point I guess, there may be too much coolant running around the turbo and heater circuit rarther than the radiator. I wouldn't have thought so, I don't run water to my turbo just the heater matrix with no restrictors in the pipe and that works fine. might be worth re-inserting the restrictors though.

are there any other differences between your pipework and the 225 ?

[Matt Cole]

thats another point I guess, there may be too much coolant running around the turbo and heater circuit rarther than the radiator. I wouldn't have thought so, I don't run water to my turbo just the heater matrix with no restrictors in the pipe and that works fine. might be worth re-inserting the restrictors though.

are there any other differences between your pipework and the 225 ?

Yeah the restrictors are in place scoff. I know nothing really on how the 225 system is hooked up, as i cant get any info on it, cant be much different from the 172 though but with a turbo cooling circuit added. I know the water pump is of a different configuration to the 172 but its pretty much the same. I'll take another look and map out how i have it plummed in.

[Adam 005]

It seems strange that the stat opens at 100 degs a full 11degs after it should.what gauges are you using to measure the temps

[Ashy]

It is a weird one, if i compare it to mine it. From cold it heats up to about 90 degrees, the stat opens and the temp drops to about 80 degrees, it then rises back to about 85 and stays there.. it may creep up to 90ish but is kept in check with the fan...

Mats just rises to 100 then the stat opens and it drops (in about 5 seconds) back to 80 then climbs back up to 100 and drops to 80.... It just keeps repeating this over and over?!?

Maybe it would be worth just drilling a small 2mm hole in one of your spare stats and giving it a shot m8?

[Adey aka Ewok]

try a different stat? is the water still going the wrong way through the rad?

[Ashy]

water is going the right way now... He's treid a few stats (one of which was a 172 stat) all do the same.

[Adam 005]

could the water in the rad only be flowing when stat is fully open.Is there a total lack of flow when stat is not open.
Is there air in the system causing the water pump to cavatate.

You could try half covering the rad remove stat and drive to see if cooling system preforms better.This may help to rule out stat problems.

i'm no expert in these mattres but it might help:agree::agree:

[Matt Cole]

ive drilled a 4mm hole in the stat today and it now holds about 80 deg. I think 4mm might have been a bit big but it seems to work. Strange really. Not sure how quick it will get up to temp on the move though.:agree:

[Adey aka Ewok]

could there be somthing wrong with the engine? slight hg leak into a cylinder causing the temp spikes?

[Matt Cole]

could there be somthing wrong with the engine? slight hg leak into a cylinder causing the temp spikes?

god i hope not!!! na mate does'nt seem to be burning water and the stat drilling proves water is circulating.

[Matt Cole]

temp going up and down sounds like its air locking, are you running a pipe from the top port of the stat housing to the top of the header tank ? you need this to get rid of air that might otherwise pile up in front of the thermostat.

if the header tank is piped as above then you should be getting water running in to the header tank through that small pipe, especially when the stat is closed. is this happening ?

if all that sounds OK then have you tried a new stat incase that one's buggered ?

the rad won't be too big.

Scoff, the bleed pipe from the top of the stat housing exits after the stat (flow direction of water) so can't see flow unless the stat opens?? Should there be some water flow pastr the stat even when its shut?? As mentioned iv'e drilled a 4mm hole and the rad heats up gently and holds about 80 deg on the road.