K Series Coolant Issues - Looking for guidance

[6Sel]

I’m looking for your collective wisdom with a coolant issue that has got me stumped, with the well earnt reputation of the Rover K series head gaskets its I guess I’m thinking that maybe the issue but before I go down that route looking that I have covered all option.

Apologies in advance for the long post.

Vehicle

Superlight R fitted with the 1800 VHPD K Series with heater

Symptoms

On the road the vehicle performs well with no evidence of overheating or loss of fluids although does always appear to run hot (90°C on gauge).

Each of the three trackdays I’ve done since owning the car has resulted in some coolant related issue.

Trackday 1 – Car performed well all day until the final session of the day when vapour traces was evident jetting from two pin holes in the (aluminium radiator).

Radiator replaced with replacement ‘red’ coolant mixed 50:50

 Trackday 2 – During the day spent time bleeding through the radiator (with the front raised), after each session the coolant level had dropped although no evidence of coolant escaping from the pressure cap seen. In the middle of the afternoon the top heater hose split releasing coolant. It was also noted that the radiator had ‘bowed’ on the top and bottom rails.

Hose replaced and checks detailed below performed

Trackday 3 – After each session traces of coolant evident around the expansion bottle from the pressure cap lifting. In the lunch break when the vehicle had cooled able to get a further 1.1/2 litres of coolant in the radiator by filling through the vent fitting (with the vehicle raised at the front).

At the end of the afternoon session the cap lifted releasing qty of coolant.

Work / Checks undertaken to-date

Radiator replaced

Vehicle ran up to temperature with pressure gauge in place of the pressure cap – no high readings (max below 1 bar)

Coolant system pressurised through the expansion bottle to 1 bar, no deterioration seen over an extended period (5 days)

Expansion Bottle Cap Replaced

Suggestions

Welcome suggestions on next steps, it feels like the system is pressurizing when used on the track. My next steps were to replace the water pump (deteriorating and not creating the necessary flow?) and thermostat.

Reluctant to replace the head gasket as it appears sound with the tests performed above although is it heard of for the stretch bolts to stretch when hot releasing tension on the gasket then re-seating when cooled down?

Appreciate any guidance you may have - once again, apologies for the long post.

Thanks,

Chris

 

[Jonathan Kay]

What temperature thermostat are you using? 

Does the fan come on when needed and not otherwise?

You've replaced the radiator and split hose and the expansion bottle cap. Are you sure you have the right sort of cap? Please add a photo if not.

Beyond those failed bits I'm not sure I'd suspect anything beyond the dreaded air lock. You have a heater and you're lifting the nose. Do you have a bleeding T-piece? Does the thermostat have the extra hole?

Jonathan

[6Sel]

Jonathan,

Thank you for your quick reply.

I have not removed the thermostat so not sure what temperature it is, other club members have suggested I remove it and check it has been modified (by drilling a relief hole) so as to reduce the thermal shock when it initially opens. The cooling fan cuts in and out as expected and the cap was purchased from Caterham online parts store with >PA66-GF30< embossed on the underside (I'll post the photo when I work out how to do that).

It would be good to think it was simply an airlock (I don't currently have a T piece bleed in the top heater hose), just cannot figure out in mind how such a pressure can be generated to deform the radiator.

Best Regards,

Chris

[Jonathan Kay]

I'll post the photo when I work out how to do that

Forum User Guide

Jonathan

[6Sel]

Jonathan,

Photo below;

Thanks for the instructions.

Best Regards,

Chris

 

[Silver Machine]

My only experience is with a 1600 super sport which is a different engine in some ways but in other ways has some common ground. Had similar problems and it turned out to be a ball valve in the inlet manifold. It had seized up and needed releasing. To sort things out in my case involved:

Remove tube from header tank to inlet manifold.

Use a piece of stiff or twisted wire to poke into the hole in the manifold

This  released the seized ball valve.

This may not be the issue with your engine but worth trying as it costs next to nothing and takes about 10 minutes in time

I must give acknowledgment to Richard Price for pointing me in this direction before I started on a possible head gasket replacement.

[paul mel]

Another thing to consider looking at would be the inlet manifold gasket, mine had failed around the forward water port.

I also found the fitment of a QED remote thermostat made the cooling system much less susceptible to air locks and a lot more stable in general.

[6Sel]

Thank you for all the replies.

I have had a little time over the weekend to investigate further, I removed the air-filter, back plate and throttle bodies so that I could better see the rear of the water pump / thermostat.

A fellow member who built a similar powered car a number of years ago suggested I removed and inspected the thermostat but even with the above removed am struggling to find it.

The bottom (large) hose from the radiator goes directly into the back of the water pump (with a tee piece off into the expansion bottle), the smaller hose from the water pump goes directly to the heater control valve. On the return side, the output from the heater goes via the diverter valve down into the solid water rail with a sender at the rear of the engine (brown multi plug) then another sender (single wire – gauge sender?) then into a large hose into the top of the radiator.

There is another small hose from the expansion bottle back into the inlet manifold which I have removed so as to clean the non-return ball valves (thank you Silver Machine) – it did seem to be gunged up.

I’m now intending to pressure test the system again now that it is drained from coolant (to eliminate a false reading caused by an airlock) but would like to find the thermostat location is this contained within back of the water pump?

One final thing – I assume unrelated, by the inlet manifold between cylinders 2 and 3 there was a foam air filter pointing down, this had disintegrated so will replace but was wondering what the correct term is for it (picture below).

Once again, thanks for all the help.

Chris

[SM25T]

Yes ... It is in the black plastic housing on the rear of the water pump. Held in place by the bolt that secures the diptube.

[tin duck dave]

Could be head gasket. Mine had a tiny break in a fire ring which allowed pressurised the cooling system giving the coolant being forced out symptom you have. Fine in gentle road use but couldn't handle track levels of performance. Could get about 2/3 of a lap of nurburgring before it would start blowing past header tank cap.