Overheated But No warning lights and temp gauge normal?

[J44EAG]

If you don`t already have one, suggest you get a infra-red heat sensing gun. Loads on ebay and cheap as chips. They are worth their weight in gold to find hot spots. When I hand a boat back to a customer after engine cooling system overhaul, my final shot before presenting my invoice is to show them various temperatures at vital points on the installation. That proves a proper job with a quantifiable result. "No problem with the huge bill, is there, Guv?"!

You could certainly experience rough running if a head gasket had given up. Look for oil in the coolant and coolant in the oil. Both faults would need urgent attention.

The S-type on which my advice is based, is very similar in cooling operation to the 308 and indeed the K8. What I found on the S-type was that if after a fast run, a brief sit in traffic and then arrival at Forum HQ then set the fans going (even on a hot day), then my first action was to check coolant level. Low coolant meant the fans came on. In normal use with the car in apple pie order, those fans never operated. If they did, then there was an issue to deal with urgently...or blow up!

I`d suggest a new metal impeller type water pump be fitted before going much further. If a plastic impeller is currently fitted and is broken and missing lumps of it, then there could be debris in the cooling system. The lowest point is the place to investigate for missing pieces of plastic impeller. That is a nice job. Try not to get wet! If the impeller is slipping on the shaft, that is less of an issue and binning it is a nice easy option.

Note the two extra bolts on the 4.2 pump which make it distinguishable from the plastic impeller type on typical 3.2/4.0 cars of the period. Fitting is straight forward and a new gasket is recommended. Burp the system again and let the thermostat open before adjusting coolant level and putting the cap back on.

See how you get on.

Mike K

[rod3751]

OK Thanks Mike. Pump ordered and due Friday, will drain down and remove items tomorrow.
Deep joy. At least i sold my boat and can look for another,Just haven't got anything to tow with until jag fixed.
Rod