[g259fsg]

Our 1990 214 has been showing some slightly abnormal behaviour recently. As some of you know, we took it down to POL, and apart from alternator problems the engine itself seemed to be running fine. Things have been complicated because I recently had to fit a new thermostatic radiator fan switch and have had trouble getting a good seal to the radiator. It's a bit of bad design and can take several goes to get a reliable seal. So, I've been losing some coolant and have had to drain the system about three times. I'm careful to remove airlocks when refilling but it always possible there was some air left in it. I've been monitoring it over the last three weeks, and have found some coolant loss, I think, but nothing dramatic. No obvious leaks from hoses, thermostat housing etc.

The other thing I noticed was that the tick-over was a bit uneven when starting-up (slight misfiring), but that usually cleared in about 10 seconds. I wondered if this was due to some coolant leaking into one of the cylinders through the HG or inlet manifold gasket, when the car has been standing for a while. I did a compression test and when I took out the plugs, No.2 looked a bit dodgy. It had some brown streaking up the insulator and black deposits on the electrodes as though it hadn't been firing properly. The other three looked normal grey/brown. I replaced them with a new set of Bosch FR78X, the same as what had been in. They had done 13000 miles. I did another hot compression test a few days later and the new plugs were all very clean after about 50 to 70 miles, and the running is better though not perfect.

These are the compression figures I got

Cold Hot
1 130 120
2 125 120
3 130 120
4 130 110

The other worrying symptom is that the coolant system does seem quite pressurised when it's hot, the top coolant tank is pretty well empty, though it comes back more or less to the right level when cold. When the engine is really hot, releasing the coolant cap very slightly, the coolant comes surging back in under pressure through the two vent hoses and would overflow the tank if left open. The vent hoses are clear including the one to the O/S end of the inlet manifold. There seems to be quite a lot of gas/steam forcing the coolant back.

I got one of these combustion gas leak testers:

https://www.drheadgasket.co.uk/COMBUSTI ... dgasket-uk

It didn't detect any combustion gases, but not sure how reliable it is. Has anyone else used this kit?

One final issue is that I replaced the thermostat a couple of years ago (the original one was opening too early and ran the engine too cool). The new one I got from Rimmers PEL10016 is rated at 88 deg C whereas the original one was 82 deg C, so it's possible the engine is much closer to boiling point. Of course it might be opening at an even higher temperature now. I should have tested it before installation. Incidentally, the temperature gauge always reads normal, slightly below middle, even when on the motorway. I'm wondering if the problem would be eased if I fitted a lower temp thermostat. Pity it's such a big job to change it. Has anyone fitted a remote thermostat like this one:

https://qedmotorsport.co.uk/wp-content/ ... itting.pdf

I'm going to do some more tests with a digital thermometer to see what the actual temperatures are.

Basically, I'm a bit worried about driving the car at the moment and getting overheating. There is no oil contamination in the coolant or coolant in the oil, so neither of the classic HGF symptoms. The head gasket was replaced and the head skimmed in 2005. The head gasket was an uprated one in the set LVQ701201EVA.

Would be grateful for any advice or suggestion of further tests I could do.

Hugh

[itcaptainslow]

Those compressions, while even, look rather low-from memory 10 bar/145psi is the minimum for a K-Series, and healthy engines I've tested have usually given figures of 160-180psi. The next step I'd suggest here would to be conducting a leak test on the engine, where compressed air is forced into each cylinder in turn with the valves closed to listen for an air escaping. If it's coming out of the exhaust or inlet tract, then it's a valve sealing issue. If the leak is further down (e.g. into the sump) then it's a piston ring issue. A garage should have the equipment to do this. This will help diagnose if it's a mechanical problem with the engine internally or something else. Those kind of compression figures I've seen before when the timing is a tooth or two out...

I wouldn't expect to see black deposits on a plug with coolant leaking into the cylinders. Has the cooling system been pressure tested to check for an external leak?

The pressurisation of the cooling system as you describe doesn't sound normal, either. I'd expect with this behaviour to get a positive result on the combustion gas leak detector though...those "sniff" testers which react with combustion gases in the coolant are usually pretty good! I've got one and it's always been accurate. The colour of my test fluid is blue, changing to green if there's slight contamination, and yellow if it's really bad news! You do sometimes have to leave them on the car with the engine running at a fast idle for ten minutes or so to get an accurate result, together with squeezing the bulb at the top to draw through the test fluid.

Not sure where you are but if you're local to me (Bedfordshire) I'm happy to try my tester on your car to compare results.

Edit-just seen you're north of the border

[g259fsg]

Thanks for those insights. It's given me a few more ideas. I agree, the compression figures seem a bit low, however I'm now wondering if when I took the second set of hot numbers, did I have the throttle open. I remember doing it first time but not the second. Maybe should do those again. I was surprised they are a bit low. Using the same tester, I typically get about 160 psi on the Humber Sceptre (which is 9.5:1) and about 145 psi on the Super Snipe which has a lower compression engine.

If the engine had a lot of wear or the valves were leaking, I'd expect loss of performance whereas it seems fine and was impressive on the trip to Birmingham in April. I got nearly 47 mpg overall at typical motorway speeds of 70 to 75 mph. Didn't feel like a worn engine. I'm at the local garage for an MOT on Monday, so I'll ask them about doing some further pressure tests.

I'll try the HGF tester again. There was so much coming up when the engine is hot that it took out the fluid from test kit. Seemed too much to be coming from combustion gases, more likely steam. I'll try doing it when the engine is cooler.

Will report back.

Thanks for your help,

Hugh

[itcaptainslow]

Definitely worth doing another test then with the throttle open-also do a test on one of your other cars at the same time, just to rule out a defective compression tester.

Keep us posted!

[g259fsg]

Have repeated the compression test with the engine hot and the throttle held fully open. This is what I got:

1 140 psi
2 140 psi
3 140 psi
4 135 psi

Better than the last lot of results, although a bit lower than I expected for this engine. No.4 appears to be down slightly, and when I took the old plugs out, the electrodes on that were a brown colour, whereas 1 and 3 were light grey. No.2 was a faulty plug (as mentioned in my first message), so I replaced all four and they are now quite uniform in colour. I did use the compression tester (without the extension tube) on the Minx and got 150 psi with the engine cold, so I think the gauge is fine.

I also had another go with the headgasket test kit. The problem was the coolant backing up into the coolant tank quite quickly when the engine is hot, and this interfered with the test. I siphoned out some of the coolant and also ran the heater/fan at full to help extract heat from the engine. As I said previously, the temperature gauge always shows normal so although I've got an 88 deg C thermostat rather than 82 deg C, I don't think it is the cause of the problem. If it was more accessible, it would be nice to take it out for testing.

Running the engine from a cooler start, I did find the blue fluid turned a greeny-yellow after a few minutes and there was a steady stream of bubbles coming through from the coolant tank. It also increased if I revved the engine. I'm now fairly convinced there is leakage of combustion gases into the coolant circuit. There's certainly something pressurising the cooling system.

I'll ask at the garage tomorrow if they can do some further pressure tests to diagnose the problem. Although the engine runs nicely and drives OK, I wouldn't be happy taking it any distance at the moment.

Thanks for the advice,

Hugh

[Mr Teddy Bear]

My experience with a M reg' 414 was that the temp' gauge was very sensitive to change.

They are very difficult to bleed after a coolant change mine took around a month to get all of the air out.

Despite the low volume of coolant in the system the fan shouldn't activate unless your sat in traffic.

If your model has the fan switch or thermistor fitted to the rad, a simple test of the switch is to remove the connector and bridge it; the fan should run continuously with the igition on.

A hot system will be pressurised, its designed that way to raise the boiling point of the coolant.

I have read that the MLS head gasket is thicker and thus will lower compression compared to an alternative [ that's why Matt from Furious Driving didn't have one fitted].

[itcaptainslow]

Running the engine from a cooler start, I did find the blue fluid turned a greeny-yellow after a few minutes and there was a steady stream of bubbles coming through from the coolant tank. It also increased if I revved the engine. I'm now fairly convinced there is leakage of combustion gasses into the coolant circuit. There's certainly something pressurising the cooling system.

On that evidence, I’d say the head gasket is starting to fail. Off with her head, Sir…

It’s a massive subject in itself but don’t order a head gasket until the engine has been stripped and the cylinder liner heights checked-if they’re low or uneven, you’ll definitely be wanting an elastomer gasket.

[g259fsg]

Hope I did get all the air out of the system when I refilled it. I fill with the heater control fully on and the bleed screw out of the coolant rail until coolant starts to come out, then put it back in. Usually find a run up to full temperature so that the thermostat opens is enough to clear the air. You then need to top up again. Some folk have suggested drilling a 3 mm hole in the thermostat to help with the bleeding.

I agree, the hot system is pressurised by the pressure relief valve in the coolant cap, however this seems a lot more active than that. Looks like it wants to boil over when I try to release the cap, as though there is gas or steam building up somewhere. Don't remember that effect before things started playing up. It is a bit confusing as the symptoms aren't that hard.

The fan thermostatic fan switch is working. If I leave it running in the garage, the fan does come on intermittently. I checked all that fully after I had to replace it recently. As mentioned the temperature gauge reads normal and steady after the warm-up. I'll do some checks on actual temperature when I get the digital thermometer.

Having read the article on the DMGR website, I'm now aware of the head gasket options available. I agree it is probably wise to go for the elastomer version, presumably with the lower tensile stretch bolts.

https://www.dmgrs.co.uk/pages/choosing- ... gasket-kit

I'll report back when I've seen the garage folk tomorrow.

Thanks for your help,
Hugh

[Vinny1979]

I have always re used the bolts without issue but each to their own !

[961tat]

I have always re used the bolts without issue but each to their own !

Yep same here 1.4/1.6 same bolts the only time I have used 10 .9 bolts is when I have built 1.8 that have been ported and mapped .