1969Mk3Spitfire Posted March 24, 2022 Report Share Posted March 24, 2022 As you may know, I’ve just replaced the heater valve. Heater had never worked since car in my ownership. First start after 4-5 months and first drive on Tuesday. Less than a mile from home, warm/hot air through the heat exchanger. Noticed that the water temp gauge didn’t move as quickly as I recalled, in fact, for a while I was thinking that it was not working. 5-10 miles from home, temp gauge started to move, simultaneously, very little warm air via the heat exchanger. Stopped for a couple of hours. On the return journey, water temp gauge behaved as expected and little heat into the cab. At home, lifted the bonnet, there was a lot of coolant spray from around the radiator cap and the expansion tank was half full (normally empty). I did not refill the radiator. Been out again today. Water temp gauge moves quickly to middle of display from cold start, very little heat coming into the cab from the heat exchanger. Expansion tank empty. It doesn’t feel right. Anyone offer and explanation, please? Link to comment Share on other sites More sharing options...
dougbgt6 Posted March 24, 2022 Report Share Posted March 24, 2022 3 minutes ago, 1969Mk3Spitfire said: very little heat coming into the cab from the heat exchanger Were you wanting heat or not? I mean was the heater on or off? What happens when you switch it the other way? Doug Link to comment Share on other sites More sharing options...
1969Mk3Spitfire Posted March 24, 2022 Author Report Share Posted March 24, 2022 Just now, dougbgt6 said: Were you wanting heat or not? I mean was the heater on or off? What happens when you switch it the other way? Doug Yes, Doug, I wanted heat. I tried full in and full out, the new valve has opposite actuation compared to the one removed and I’m very easily confused and can’t quite recall which is which, so tried both and also in the middle. Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 24, 2022 Report Share Posted March 24, 2022 i would also undo the highest hose clip and pull the hose off enough to let any air lock out do this with the engine idling if this doesnt work think about replacing the thermostat use a 82c stat. Pete Link to comment Share on other sites More sharing options...
1969Mk3Spitfire Posted March 24, 2022 Author Report Share Posted March 24, 2022 Just now, Pete Lewis said: i would also undo the highest hose clip and pull the hose off enough to let any air lock out do this with the engine idling Pete Will do, Pete……..a small hose near the heater or engine top hose? It felt as though the temp sender was measuring coldish water until the radiator cap blew, then all returned to normal. I seem to be back where I started with no heater but new valve 😂 Link to comment Share on other sites More sharing options...
NonMember Posted March 24, 2022 Report Share Posted March 24, 2022 24 minutes ago, 1969Mk3Spitfire said: It felt as though the temp sender was measuring coldish water until the radiator cap blew, That can happen if there's a big air lock in the thermostat housing. The sender and the stat are both measuring the air, so they stay cold. Meanwhile the engine is getting really hot (so the heater works better than ever)... until the pressure cap opens and sprays water out and - if you're lucky - the air lock escapes too. Worth making sure your thermostat has the bleed hole in the rim. Link to comment Share on other sites More sharing options...
johny Posted March 24, 2022 Report Share Posted March 24, 2022 Also, as an observation, surely the expansion bottle should always be at least half full so coolant can be drawn back into the system when it cools? Link to comment Share on other sites More sharing options...
1969Mk3Spitfire Posted March 24, 2022 Author Report Share Posted March 24, 2022 37 minutes ago, NonMember said: That can happen if there's a big air lock in the thermostat housing. The sender and the stat are both measuring the air, so they stay cold. Meanwhile the engine is getting really hot (so the heater works better than ever)... until the pressure cap opens and sprays water out and - if you're lucky - the air lock escapes too. Worth making sure your thermostat has the bleed hole in the rim. That makes sense, thanks. My car is now back in the garage with its cover on as I’m doing a bit of sailing malarkey next week. I’ll check upon my return. Where is the bleed hole and how does it function? There’s no evidence of coolant leakage around the pump or thermostat housing, from memory. Link to comment Share on other sites More sharing options...
1969Mk3Spitfire Posted March 24, 2022 Author Report Share Posted March 24, 2022 20 minutes ago, johny said: Also, as an observation, surely the expansion bottle should always be at least half full so coolant can be drawn back into the system when it cools? I agree with your observation. For the last couple of years, I’ve half filled the expansion tank with new/clear coolant. It seems to have never discoloured so I concluded that there is no expansion/contraction flow. Strange. Link to comment Share on other sites More sharing options...
johny Posted March 24, 2022 Report Share Posted March 24, 2022 I have a clear pipe so I confirm its always full of coolant plus the level in the expansion bottle goes up quite a lot when hot. I think the only way this wont happen is if theres a pocket of air in the system somewhere which absorbs the expansion of the coolant when heated so it doesnt get pushed out to the bottle. However we've talked about this before and there maybe cars that dont have a bottle so the excess just runs onto the road and as a result the radiator is never stays full. This pocket of air in the top of the rad then stops any more coolant being expelled. The type of system depends on the rad cap used as to be able to draw coolant back into the system it has to have a small spring loaded reverse flow valve under the main relief valve... Link to comment Share on other sites More sharing options...
NonMember Posted March 24, 2022 Report Share Posted March 24, 2022 51 minutes ago, 1969Mk3Spitfire said: Where is the bleed hole and how does it function? The thermostats originally fitted had a small hole with a plastic float hooked in it, in the middle of the flat ring around the mechanism. This was intended to allow air to pass up through when re-filling the cooling system. The bit of plastic might (or might not!) have then sealed the hole once the block and head (and pump housing) were full. Most current after-market thermostats don't have this, so if the engine is cold when you replace the coolant, you get an air lock. Some knowledgeable people recommend drilling a small hole - it only needs to be a couple of millimetres so it won't give much flow when cold. Link to comment Share on other sites More sharing options...
daverclasper Posted March 24, 2022 Report Share Posted March 24, 2022 Few things I understand can affect the expansion bottle working. Cap must be sealing top and bottom (Also bottom seal must seating on the lower filler neck flange, as there are different lengths of cap, mine was too short and I spaced it out with a thick washer, with an extra seal underneath it). The hose must have no leaks. The top of filler neck must be flat, or the cap top seal, won't. I had all these issues, though now fine 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 24, 2022 Report Share Posted March 24, 2022 what is the bleed hole /jiggle pin simple wiggly thing in a hole in the rim there are a few variations but finding a picture has been a faf most shonw by our suppliers dont have the bleed , it is most important as it lets air out when the stat is fully closed if you dont have one when refitting one just add a 2-3 mm hole drilled in the rim to let trapped wind escape Pwete Link to comment Share on other sites More sharing options...
Nick Jones Posted March 24, 2022 Report Share Posted March 24, 2022 4 hours ago, NonMember said: That can happen if there's a big air lock in the thermostat housing. The sender and the stat are both measuring the air, so they stay cold. Meanwhile the engine is getting really hot (so the heater works better than ever)... until the pressure cap opens and sprays water out and - if you're lucky - the air lock escapes too. Worth making sure your thermostat has the bleed hole in the rim. This. The jiggle pin or plain hole in the thermostat matters in these circumstances. You sometimes get away without if the thermostat just plain doesn’t seal well enough to stop air passing through it. Nick Link to comment Share on other sites More sharing options...
1969Mk3Spitfire Posted March 25, 2022 Author Report Share Posted March 25, 2022 Thanks to all for your words of wisdom. I’ve done a bit of tinkering this morning and, based upon the engine idling on the drive, it now seems to be working much better. Sadly, I don’t have time to take the car for a drive, it will have to wait a couple more weeks. There’s no jiggle pin to be seen so I “burped” the hose going into the heater valve. I’ll also keep an eye on the expansion bottle. After being off the road for approx 30 years, it’s restoration was completed at the end of 2019. A year ago, I changed the coolant but I’m not altogether happy with its colour now, black, so I may use a proprietary flush and refill. Any suggestions for a favoured brand? Prestone? Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 25, 2022 Report Share Posted March 25, 2022 a couple of cupfuls od cheap washing soda crystals for a hot flush and a few good drives to circulate it flush out twice with a hose etc to clear the mixture . and any blue /glycol antirfeeze will work ok make is by your preference do not use pink OAT they wont mix at all . Pete Link to comment Share on other sites More sharing options...
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